U.S. patent application number 11/760208 was filed with the patent office on 2007-12-06 for switching pattern ac induction motor.
Invention is credited to Wei Huang, Youguo Huang.
Application Number | 20070278890 11/760208 |
Document ID | / |
Family ID | 27735508 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070278890 |
Kind Code |
A1 |
Huang; Youguo ; et
al. |
December 6, 2007 |
SWITCHING PATTERN AC INDUCTION MOTOR
Abstract
Both the stator core and the rotor core of a switching pattern
AC induction motor are fabricated by soft magnetic material
laminations or ferrite material, etc., both of which have
corresponding frequency characteristic. The excitation voltage is
sine wave pulse width modulated or sine wave pulse amplitude
modulated within the frequency range of voice and ultrasonic. Under
the condition of the same power output, the present motor reduces
its size and mass to a fraction of or tenth of that of an ordinary
one. Meanwhile, it reduces the cost of manufacture. It realizes
stepless speed regulating from zero to several thousand rpm while
keeping well mechanical characteristic performance.
Inventors: |
Huang; Youguo; (Wuhan City,
CN) ; Huang; Wei; (Wuhan City, CN) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
27735508 |
Appl. No.: |
11/760208 |
Filed: |
June 8, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10504023 |
Sep 24, 2004 |
7239061 |
|
|
PCT/CN03/00017 |
Jan 9, 2003 |
|
|
|
11760208 |
Jun 8, 2007 |
|
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|
Current U.S.
Class: |
310/211 ;
310/166; 318/811 |
Current CPC
Class: |
H02K 3/28 20130101; H02K
17/16 20130101; H02K 17/12 20130101 |
Class at
Publication: |
310/211 ;
310/166; 318/811 |
International
Class: |
H02K 17/16 20060101
H02K017/16; H02K 1/16 20060101 H02K001/16; H02P 27/04 20060101
H02P027/04; H02K 1/26 20060101 H02K001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2002 |
CN |
02115544.5 |
Feb 9, 2002 |
CN |
02228424.9 |
Claims
1. A switching pattern AC induction motor comprising a machine
base, a stator and a rotor, said stator including a core with
stator teeth and grooves disposed alternately and excitation
windings being disposed in the stator grooves, and said rotor being
of a squirrel cage structure with metal conducting bars, wherein
the number of the stator grooves or teeth being determined by the
following equation: Z=2*M*P*Q, where M being the number of phases
of excitation voltages applied to the excitation windings, P being
number of pairs of stator poles, and Q being the number of grooves
or teeth per pole per phase; said excitation windings on the stator
of the motor being excited by a sine wave switching AC pulse
modulated excitation voltages, and the number K of the metal
conducting bars in the rotor `squirrel cage` being twice of the
number P of pairs of the stator poles, i.e. K=2*P*Q, wherein, the
sine wave switching AC pulse modulated excitation voltages are
generated by performing pulse width modulation or pulse amplitude
modulation on two phases of continuous modulating sine wave
voltages with phase difference of 90 degree or three phases of
continuous modulating sine wave voltages with phase difference of
120 degree with equal virtual values and frequencies, together with
a pulse square wave voltage having a waveform of symmetric square
wave with a duty factor of 50% of which the frequency (F2) is
within the frequency range of voice or ultrasonic and much larger
than the frequency (F1) of said continuous modulating sine wave
voltages.
2. The motor according to claim 1, wherein the frequency (F1) of
the continuous modulating sine wave voltages determines the
rotation speed of the motor, and can be changed to perform speed
control of the motor.
3. The motor according to claim 1, wherein the resistance of the
excitation windings of the motor is proportional to the frequency
(F2) of the pulse square wave voltage, and the higher F2 is, the
smaller the size and mass of the stator core, the rotor core and
the windings of the motor are.
4. The motor according to claim 1, wherein said motor is of a
cylinder type by disposing said rotor on inner side and the stator
on outer side, and said stator core is of cylinder shape, and said
stator teeth are disposed on the inner surface of said stator core
in equal angles and extending inward along a radial direction with
stator grooves penetrating along an axial direction between the
teeth, and said metal conducting bars of the `squirrel cage` being
disposed along the axial direction and distributed at equal
intervals in parallel with a cylindrical surface of the rotor.
5. The motor according to claim 1, wherein said motor is of a
cylinder type by disposing said rotor on outer side and the stator
on inner side, said stator core is of cylinder shape, and said
stator teeth are disposed on the outer surface of said stator core
in equal angles and extending outward along a radial direction with
stator grooves penetrating along an axial direction between the
teeth, and said metal conducting bars of the squirrel cage being
disposed along the axial direction and distributed at equal
intervals in parallel with a inner cylindrical surface of the
rotor.
6. The motor according to claim 1, wherein said motor is of a disk
type motor, said stator core and said squirrel cage of said rotor
are of a ring shape, and said stator teeth are disposed on a plane
vertical to an axis of said ring shape along a radial direction on
the surface of said stator core in equal angles with stator grooves
penetrating along the radial direction between the teeth, and said
squirrel cage includes metal conducting bars disposed along the
radial direction and distributed at equal intervals and conducting
rings to form a squirrel cage of a disk type.
7. The motor according to claim 1, wherein, when the number of
grooves or teeth per pole per phase is Q=1, the excitation windings
on the stator adopt centralized windings with 1/M pole pitch or
integral multiple pitch.
8. The motor according to claim 1, wherein, when the number of
grooves or teeth per pole per phase is Q>1, the excitation
windings on the stator adopt distributed windings.
9. The motor according to claim 1, wherein cores of the rotor and
the stator are made by soft magnetic material laminations which
meet corresponding frequency characteristics (F2) within the
frequency range of the pulse square wave voltage, and subject to
surface insulation treatment, then to piling along the axial
direction, or made of ferrite materials with corresponding
frequency characteristic as a whole or in a manner of sectioning
along the axial direction.
10. The motor according to claim 6, wherein the stator core and the
rotor core are made by belt-shaped soft magnetic materials which
are subject to surface insulation treatment, and then wrapped along
the axial direction to form a shape of disk, and treated along the
radial direction to form grooves or teeth, or made of ferrite
materials with corresponding frequency characteristic as a whole.
Description
[0001] This application is a Continuation-In-Part of copending
application Ser. No. 10/504,023 filed on Sep. 24, 2004 the entire
contents of which are hereby incorporated by reference and for
which priority is claimed under 35 U.S.C .sctn.120.
TECHNICAL FIELD
[0002] The present invention relates to a novel motor, more
particularly, to a switching pattern AC induction motor within the
frequency range of voice and ultrasonic.
BACKGROUND ART
[0003] Existing AC induction motor, which is mainly squirrel cage
type AC asynchronous induction motor, has the advantages of simple
structure, low cost and larger output torque as compared with brush
DC motor. Such a motor is typically excited with continuous two
phases of sine wave voltages with a phase difference of 90.degree.
or three phases of sine wave voltages with a phase difference of
120.degree.. A continuous sine wave rotating magnetic field is
generated in the air gap between the stator and the rotor, which
causes the squirrel cage type rotor rotating. The rotating speed of
the motor can be approximately calculated by the rotating speed
formula for the rotating magnetic field: n=60*f1/p, where p is the
number of pole pairs of the stator in the motor, f1 is the
frequency of the excitation AC. It can be seen that with the
structure of the motor fixed, the rotating speed is mainly
determined by the frequency f1. Thus, an effective way to control
the rotating speed is to vary the excitation AC frequency f1. For
example, supposing the number of pole pairs in the motor is p=2,
the rotating speed per minute is n=1500 r/min when the excitation
AC frequency f1=50 Hertz; the rotating speed is n=1200 r/min when
f1=40 Hertz, and so on. For this reason, a plurality of methods of
controlling the speed have been developed, such as
frequency-converting speed regulating and vector-controlling speed
regulating, etc. However, since the actually required operating
speed is typically much lower than the rotating speed of the motor,
and because of the resistance characteristic of the excitation
windings and the torque requirement of the motor, such as the
torque of the AC asynchronous motor is somewhat low during
low-speed running, sometimes a lower rotating speed can not be
obtained by decreasing the excitation AC frequency f1 without
limitation. Therefore, it is often required to employ at the same
time, for example, mechanical gears to vary speed, so as to meet
various requirements in actual usage. In this way, the cost, size
and weight of the apparatus are undoubtedly increased, and the
effect is not satisfying.
[0004] In the recent twenty to thirty years, permanent magnetic
brushless DC motor, step motor and switching reluctance motor,
which can be generally referred to as electronic electromotor or
electronic motor, are invented and widely used. Mostly, their
running principle is to rotate the rotor by alternatively using the
attraction force or repulsion force generated between the poles
with the different polarity by control technology. This kind of
motor has apparent improvement in aspects of speed regulating, the
size and the weight, but the cost of manufacture, the speed
regulating range and the output torque still do not meet the
increasing requirements for higher performance.
SUMMARY OF THE INVENTION
[0005] The technical problems to be solved in the present invention
are:
[0006] First, such a novel motor should have larger power density,
that is to say, under the condition of equivalent output power, the
size and mass of the motor is reduced to a fraction of or tenth of
that of an existing one.
[0007] Second, such a novel motor has larger range of speed
regulation as compared with existing motors, the output speed
thereof can be continuously stepless adjusted between the rating
rotating speed of thousands of circles per minute and zero rotating
speed, the manufacturing cost is cheaper, the size and mass is very
small, and the speed can be changed without gears while keeping
constant torque.
[0008] The technical solution adopted to solve the above technical
problems in the present invention is:
[0009] Such a motor is achieved by adopting the AC electromagnetic
induction technique with switching frequency within the frequency
range of voice and ultrasonic, thus, it can be referred to as a
voice frequency and ultrasonic frequency switching pattern AC
induction motor. Such a motor is composed of a machine base, a
stator and a rotor, said stator including a core of cylinder shape,
and stator teeth being disposed on the internal surface of said
stator core in equal angles and extending inward along a radial
direction with stator grooves penetrating along an axial direction
between the teeth; the number of the stator grooves or teeth being
determined by the following equation: Z=2*M*P*Q, where M being the
number of phases of the excitation voltages, P being the number of
pairs of stator poles, and Q being the number of grooves or teeth
per pole per phase; excitation windings being disposed in the
stator grooves, and the rotor of the motor being of a squirrel cage
structure; metal conducting bars of the `squirrel cage` being
disposed along the axial direction and distributed at equal
intervals in parallel with a cylindrical surface of the rotor,
characterized in that: said excitation windings on the stator of
the motor being excited by switching AC pulse pattern modulated
excitation voltages, and the number K of the metal conducting bars
in the rotor `squirrel cage` being twice of the number P of pairs
of the stator poles, i.e. K=2*P*Q. The excitation windings on the
stator are excited by switching AC pulse pattern modulated
excitation technique, and the excitation voltage is a pulse
modulated voltage, which can be referred to as a sine wave pulse
modulated excitation voltage, generated after pulse width
modulation or pulse amplitude modulation is performed on two phases
of continuous sine wave voltages with phase difference of
90.degree. or three phases of continuous sine wave voltages with
phase difference of 120.degree., which can be referred to as
modulating sine wave voltages and have equal virtual values and
frequencies, together with a pulse square wave voltage within the
frequency range of voice or ultrasonic, which can be referred to as
a modulating square wave voltage. When Q=1, the structure of the
excitation windings on the stator adopts centralized windings with
1/M pole pitch or integral multiple pitch. When Q>1, the
distributed windings are adopted. The cores of the rotor and the
stator are made by soft magnetic material laminations which meet
corresponding frequency characteristics within the frequency range
of voice and ultrasonic, and subject to surface insulation
treatment, then to piling along the axial direction, and it can
also be made of ferrite materials with corresponding frequency
characteristic as a whole or in a manner of sectioning along the
axial direction.
[0010] The most essential innovation of the novel motor according
to the present invention is the innovation of the excitation
technique, i.e. it is excited by sine wave pulse modulated voltages
within the frequency range of voice or ultrasonic, when the
excitation windings in the stator ate excited, the required
pulsating alternating rotating magnetic field is generated in the
air gap between the stator and the rotor, induced current is
generated in the conducting bars on the rotor, and the torque of
electromagnetic force in such a pulsating alternating rotating
magnetic field is applied on the conducting bars, so that the rotor
of the motor rotates. Supposing the frequency of the modulating
sine wave voltages is F1, the frequency of the modulating square
wave voltage is F2, when the motor operates, the rotating speed of
the pulsating alternating rotating magnetic field only depends on
the frequency F1 of the modulating sine wave voltages, and is
independent of the frequency F2 of the modulating square wave
voltage, thereby the speed regulation of the motor can be achieved
by changing the frequency F1 of the modulating sine wave voltages
with a control circuit. Since the pulse frequency of the sine wave
pulse modulated excitation voltages, i.e. the pulsating alternating
frequency of the rotating field, equals to the frequency F2 of the
modulating square wave voltage with its value within the frequency
range of voice or ultrasonic, and is much larger than the frequency
F1 of the modulating sine wave voltages. It can be derived from the
basic principle of the electromagnet theory that, the resistance of
the excitation windings of the motor is proportional to frequency
F2, and is independent of frequency F1 of the modulating sine wave
voltages. The higher F2 is, the smaller the size and mass of the
stator core, the rotor core and the windings of the motor are. As
long as the frequency F2 is maintained to be relatively fixed, a
stable output torque of the motor can be ensured even when the F1
approaches to zero frequency to obtain an extremely low rotating
speed, thereby the continuous stepless speed regulation between the
rating rotating speed of thousands of circles per minute and zero
rotating speed can be achieved under good mechanism characteristic.
Since the size of the motor is reduced, materials consumption can
be greatly saved, and the stator core and the rotor core can adopt
cheaper soft magnetic materials, so the manufacture cost can be
greatly reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a transverse sectional view of the stator and the
rotor in a two-phase motor with 16 grooves and 4 pairs of
poles.
[0012] FIG. 2 is a schematic diagram of connection of the 1/2 pole
pitch excitation windings of the motor shown in FIG. 1 and the
excitation voltages.
[0013] FIG. 3 is a stretch-out view of the 1/2 pole pitch
centralized excitation windings in the motor shown in FIG. 2.
[0014] FIG. 4 is a schematic view of the waveforms of the sine wave
pulse modulated excitation voltages in the motor shown in FIG.
1.
[0015] FIGS. 5A, 5B are a view of the pulsating and rotating
magnetic field generated by the excitation voltages shown in FIG. 4
and a schematic diagram of the running of the rotor.
[0016] FIGS. 6A.about.8B are stretch-out views of several kinds of
integral multiple pitch excitation windings in the motor shown in
FIG. 1.
[0017] FIG. 9 is a transverse sectional view of the stator and the
rotor in a three-phase motor with 24 grooves and 4 pairs of
poles.
[0018] FIG. 10 is a stretch-out view of the 1/3 pole pitch
centralized excitation windings in the motor shown in FIG. 9.
[0019] FIG. 11 is a schematic view of the waveforms of the sine
wave pulse modulated excitation voltages in the motor shown in FIG.
9.
[0020] FIGS. 12, 13 are views of the pulsating and rotating
magnetic field generated by the excitation voltages shown in FIG.
11 and schematic diagrams of the running of the rotor.
[0021] FIGS. 14A.about.16B are stretch-out views of several kinds
of centralized excitation windings in the motor shown in FIG.
9.
[0022] FIGS. 17, 18 are block diagrams of the excitation control
circuits of the motor shown in FIG. 9.
[0023] FIG. 19 is a transverse sectional view of the stator and the
rotor in a two-phase outer rotor type motor with 16 grooves and 4
pairs of poles corresponding to the motor shown in FIG. 1.
[0024] FIG. 20 is a transverse sectional view of the stator and the
rotor in a three-phase outer rotor type motor with 24 grooves and 4
pairs of poles corresponding to the motor shown in FIG. 9.
[0025] FIG. 21A-C are transverse sectional views of the stator and
the rotor in a three-phase disc type motor with 48 grooves and 8
pairs of poles.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0026] FIG. 1 shows a transverse sectional view of the stator and
the rotor in a two-phase motor with 16 grooves and 4 pairs of
poles, wherein "010" is a stator core with a shape of hollow
cylinder, "101" are stator grooves penetrating along the axial
direction, "102" is a stator yoke, "103" are stator teeth
distributed in an identical angle and extending inward along the
radial direction, the stator grooves and the stator teeth are
arranged alternatively surrounding the internal surface, "020" is a
rotor having a cylindrical surface, "104" are conducting bars
distributed in parallel with equal intervals along the cylindrical
surface of the rotor core of the motor, the conducting bars and the
conducting rings (not shown in the drawings) located at the two
end-faces of the cylinder are welded to be a metal inductor like a
squirrel cage structure, "105" is a rotor core, "106" is a rotor
shaft, "107" is the air gap between the rotor and the stator, the
rotor shaft is supported by a rotor bearing (not shown in the
drawings) on a machine base connected with the stator core as a
whole. When the number Z of the stator grooves or teeth is fixed,
if the number of the stator grooves or teeth per pole per phase is
Q=1, the number of pole-pairs and the number of conducting bars
corresponding thereto in the rotor can be increased to obtain a
larger output torque. In the embodiment shown in FIG. 1, since the
number of phases of the excitation voltages is M=2, and the number
of stator grooves [101] or teeth [103] is Z=16, when Q=1, the
number of pole-pairs is P=Z/(2*M*Q)=4, there are 8 conducting bars
in the rotor, which is twice of the number of pole-pairs.
[0027] As described above, the excitation voltages concerned in the
present invention are pulse excitation voltages generated by pulse
width modulation or amplitude modulation on two phases of
modulating sine wave voltages with a phase difference of 90.degree.
or three phases of modulating sine wave voltages with a phase
difference of 120.degree., together with a modulating square wave
voltage within the frequency range of voice or ultrasonic. The
modulating sine wave voltages can be referred to as A phase, B
phase and C phase modulating sine wave voltages respectively. For
the convenience of explanation, the excitation voltage generated by
pulse modulation on the A phase modulating sine wave voltage can be
referred to as A phase excitation voltage, the excitation voltage
generated by pulse modulation on the B phase modulating sine wave
voltage can be referred to as B phase excitation voltage, and so
on. As shown in FIG. 4, Ur is a modulating square wave voltage
having a waveform of symmetric square wave with a duty factor of
50%. Uas is the A phase modulating sine wave voltage, Ubs is the B
phase modulating sine wave voltage, and Uas leads Ubs by
90.degree.. Uwa, Uwb are respectively the A, B phase width
modulated excitation voltages, and Uma, Umb are respectively the A,
B phase amplitude modulated excitation voltages. As well known, for
a pulse width modulated excitation voltage, the pulse amplitude of
the excitation voltage is fixed, and the pulse width thereof is
proportional to the amplitude value sampled on the modulating sine
wave voltage at respective corresponding timings of modulating
square wave voltage. In the drawing, the lagging edge of each pulse
in the pulse width modulated excitation voltage is fixed at the
rising edge or falling edge of the modulating square wave voltage,
and its leading edge is variable. For a pulse amplitude modulated
excitation voltage, its pulse width is fixed, and the pulse
amplitude is proportional to the amplitude value sampled on the
modulating sine wave voltage at respective corresponding timings of
the modulating square wave voltage. It can be seen from the
drawing, the polarity orienting principle of the pulse amplitude of
the pulse width modulated or pulse amplitude modulated excitation
voltages is: when the directions of the amplitudes of the
modulating sine wave voltage and the modulating square wave voltage
are the same (i.e. both are positive or both are negative), a
positive value is taken, which is a positive pulse; when the
directions of the amplitudes of the modulating sine wave voltage
and the modulating square wave voltage are the different (i.e. one
is positive and the other is negative), a negative value is taken,
which is a negative pulse. Further, the pulse amplitudes of the
same phase excitation voltage are always alternated positively and
negatively along the time axis, except for the zero point of the
modulating sine wave voltage.
[0028] FIG. 2 shows the centralized excitation winding with half
pole pitch or 1/2 pole pitch and the schematic diagram of its being
connected with the excitation voltages, the winding has separate
excitation windings on each stator tooth, thus it can be referred
to as separate type excitation windings. For a centralized
excitation winding with 1/2 pole pitch, it is more convenient to
describe with stator teeth. It can be seen from FIG. 2 that, as for
16 stator teeth thereof, in the order of numbers 1.about.16, every
two adjacent teeth constitute one pole, for example, the teeth 1, 2
constitute the first pole, the teeth 3, 4 constitute the second
pole, the teeth 5, 6 constitute the third pole, and so on, there
are totally 8 poles. Every two adjacent poles are a pair of poles,
for example, the first and the second poles constitute the first
pair of poles, the third and the fourth poles constitute the second
pair of poles, and so on. There are totally 4 pairs of poles. Thus,
each pole includes two stator teeth and two stator grooves, thereby
includes two separate excitation windings, and are switched in one
phase of the two-phases of excitation voltages in a certain phase
sequence respectively. As shown in FIG. 2, for the odd teeth in
each pole, such as 1, 3, 5, 7 and so on, the excitation windings
switch in the A phase excitation voltage; for the even teeth, such
as 2, 4, 6, 8 and so on, the excitation windings switch in the B
phase excitation voltage. The leading-in terminals of the
excitation voltages as shown in the drawing are terminals A1 and A2
respectively for the A phase excitation voltage, and are terminals
B1 and B2 respectively for the B phase excitation voltage. Further,
it is stipulated that, when the excitation voltage is positive
pulse, the terminal "1" of respective phases of excitation
voltages, i.e. A1, B1 are the inflow terminals of the excitation
current, and are referred to as a head end; the terminal "2"
thereof, i.e. A2, B2 are the outflow terminals of the excitation
current, and are referred to as a tail end. The manufacturing
parameters of all excitation windings are identical, and it is
stipulated that when the excitation voltage is positive direction
pulse, if the magnetometive force excited, on the end-face toward
the rotor, by the stator teeth winded by the windings is N
polarity, the excitation current is always flowing in from the head
end of the winding, and flowing out frown the tail end of the
winding, that is, the current inflow terminal of the winding is
referred to as the head end, and the current outflow terminal is
referred to as the tail end. Thus, the connection relations between
the two excitation windings in each pole and the excitation
voltages should be able to ensure that: when the two phases of
excitation voltages are both positive pulses, the pole is N
polarity; when the two phases of excitation voltages are both
negative pulses, the pole is S polarity. The two poles in each pair
of poles are antithetic poles of each other, the windings excited
by the same phase excitation voltage and the stator teeth winded by
them in the antithetic poles are antithetic windings and antithetic
stator teeth of each other. The winding direction of the antithetic
windings and the connection relations of them with the excitation
voltages should be able to ensure that, the polarities of the
stator teeth excited by them are opposite to each other, i.e. one
is N polarity, and the other is S polarity. Typically, the
antithetic windings in the same pair of poles, such as the windings
of teeth 1, 3 and the windings of teeth 2, 4 in the first pair of
poles, are connected in serial to be an antithetic branch circuit
in a manner of head to head or tail to tail. Then, the same numbers
of antithetic branch circuits are further connected in serial to be
a parallel branch circuit which is connected with the excitation
voltages in parallel, so as to ensure that the resistances in every
parallel branch circuit are equal, for example, the number of the
parallel branch circuits for every phase excitation voltage shown
in FIG. 2 is .alpha.=4. FIG. 3 is a stretch-out view of the 1/2
pole pitch centralized excitation windings corresponding to FIG. 2,
in which the terminal with a dot ".circle-solid." in each
excitation winding represents the head end, and the terminal
without dot represents the tail end, each antithetic branch circuit
acts as a parallel branch circuit. Thus, the number of parallel
branch circuits for each phase is .alpha.=Z/2*M=4, which are
respectively represented by (1), (2), (3), and (4). If the
terminals A2, B2 in (1) are respectively connected with the
terminals A1, B1 in (2), and the terminals A2, B2 in (3) are
respectively connected with the terminals A1, B1 in (4), the number
of parallel branch circuits for each phase can be reduced to
.alpha.=2; if the two parallel branch circuits are connected with
each other in serial in the same manner, the number of parallel
branch circuits can be reduced to .alpha.=1. As known from the
basic electromagnet theory, when the excitation winding is switched
in the sine wave pulse width modulated or pulse amplitude modulated
excitation voltage, after the winding direction of the winding and
the connection relations between the winding and the excitation
voltage are determined, the direction of the excitation current
generated in the winding is determined in accordance with the
positive and/or negative polarity of the excitation pulse at each
timing, and the amplitude of the current is related to the pulse
width or pulse amplitude of the excitation voltage, and a
corresponding magnetomotive force is generated across the stator
teeth winded by the winding. Obviously, a larger excitation current
can be obtained by increasing the number of parallel branch
circuits, so as to meet the requirement for larger output power of
the motor.
[0029] In FIG. 5A, Fm represents the magnetomotive force generated
by the pulse modulated excitation voltage, wherein the maximum
intensity of the magnetomotive force is roughly indicated by the
number of magnetic lines of force, and the polarity of the
magnetomotive force is indicated by the arrow of the magnetic lines
of force. In the drawing, according to the connection manner
between the excitation windings and the excitation voltages, the
polarity of the magnetomotive force excited by the positive
direction excitation pulse on the corresponding stator tooth is N,
the magnetic lines of force direct from the stator tooth to the
rotor, and is represented by a downward arrow; the polarity of the
magnetomotive force excited by the negative direction excitation
pulse is S, the magnetic lines of force direct from the rotor to
the stator tooth, and is represented by an upward arrow. Since the
excitation voltage is a pulse alternating positively and
negatively, the generated magnetic field is a pulsating magnetic
field alternating positively and negatively.
[0030] Hereinafter, the rotating status of the pulsating magnetic
field alternating positively and negatively and the running
principle of the motor will be explained with an example of the
motor shown in FIG. 1, which is excited by the sine wave pulse
modulated excitation voltages shown in FIG. 4, in which the
excitation windings and the excitation voltages are connected in
the manner shown in FIG. 2 and FIG. 3, with reference to FIGS. 5A
and 5B, FIG. 5B comprises two parts on the left and on the right,
in which the column (1) on the left is a sketch view of the
amplitudes and phases of the modulating sine wave voltages Uas, Ubs
corresponding to FIG. 4, with the horizontal axis representing the
amplitude of the modulating sine wave voltage and the vertical axis
being the time axis; there are a plurality of sub-diagrams on the
right, arranged along the vertical axis in two columns (2) and (3),
each sub-diagram has the same structure, and represents a part of
the stretch-out view of the cross section of the stator and rotor
in the motor shown in FIG. 1 being cut along a line A-A' and
further dissected clockwise along the internal surface of the
stator, with the section line on the internal surface of the stator
as the horizontal axis, and its origin of coordinate being located
at the intersection point of the line A-A' and the internal surface
of the stator, so as to show, corresponding to several specific
timings shown in FIG. 4, the correspondence relations of the
magnetomotive force generated by the excitation windings and the
running status of the rotor versus the amplitude values of the
modulating sine wave voltages sampled at the timings. Supposing,
for the sampled value at each specific time, there are positive and
negative excitation pulses temporally close to each other to
correspond to it, and in the drawing, column (2) corresponds to
positive direction pulses, and column (3) corresponds to negative
direction pulses. The temporal relation between the two parts on
the left and on the right in the drawing is indicated by dot
lines.
[0031] Refer to FIG. 2 and FIG. 3, as described above, the
excitation windings of the 20 odd teeth and the even teeth in each
stator pole are respectively excited by the A phase and B phase
excitation voltages, for example, teeth 1, 3, 5, 7 etc. are excited
by the A phase width modulated excitation voltage Uwa (or amplitude
modulated excitation voltage Uma), teeth 2, 4, 6, 8 etc. are
excited by the B phase width modulated excitation voltage Uwb (or
amplitude modulated excitation voltage Umb). The letters A, B on
the stator yoke are used to represent the excitation phase sequence
for the corresponding stator teeth, the numbers drawn in box "" are
used to represent the serial number of the stator teeth, the
magnetic lines of force drawn on the section of the stator teeth
are used to represent the strength and direction of the
magnetomotive force generated on the stator teeth at respective
timings. Since the frequency F2 of the modulating square wave
voltage is much larger than the frequency F1 of the modulating sine
wave voltages Uas, Ubs, it can be regarded that the positive and
negative excitation pulses temporally close to each other in the
excitation voltages respectively have similar width (or amplitude),
and the strength of the magnetomotive force generated in the
corresponding stator teeth should also be approximately identical,
with the directions being opposite.
[0032] Referring to column (1) and the first row of columns (2),
(3) in FIG. 4 and FIG. 5B, at the timing of t=00, since the A phase
modulating sine voltage Uas has a maximal value, the positive and
negative pulses of the A phase excitation voltage Uwa corresponding
to the timing have maximal pulse width value as well (the positive
and negative pulses of Uwa have maximal amplitude value as well);
since the B phase modulated sine wave voltage Ubs is 0, the pulse
width of the B phase excitation voltage Uwb (or the amplitude of
Uma) corresponding to this timing is 0 for both positive direction
and negative direction. Therefore, the teeth number 1 and number 3
excited by the A phase excitation voltage have the maximal strength
of magnetomotive force, which are represented by four magnetic
lines of force respectively. When the excitation voltage is a
positive pulse, the magnetomotive force generated at the tooth
number 1 is N polarity, and the arrow of the magnetic line of force
directs to the rotor, the magnetomotive force generated at the
tooth number 3 is S polarity, and the arrow of the magnetic line of
force directs to the stator yoke. The strength of the magnetomotive
force generated at teeth number 2 and 4 excited by the B phase
excitation voltage is 0, so the number of its magnetic line of
force is 0 as well. Supposing the position of the rotor of the
motor is just in the state as shown in the drawing, that is to say,
the conducting bars with serial number X1 and X2 on the rotor core
are facing against exactly the middle of the stator teeth number 1,
3, then the close galvanic circuit formed by the conducting bars X1
and X2 together with the parts between the welding points on the
conducting rings of the two end-faces of the rotor can be referred
to as a X1-X2 induction circuit, which exactly faces against the
stator segment centered on the middle of the tooth number 2. Thus,
as shown in the cells in column (2), in the X1-X2 induction
circuit, the magnetic flux flowed from the stator tooth number 1
into the rotor through the air gap is exactly equal to the magnetic
flux flowed from the rotor core into the stator tooth number 3
through the air gap. Similarly, as shown in column (3), in the
X1-X2 induction circuit the magnetic flux flowed from the stator
tooth number 3 into the rotor core through the air gap is exactly
equal to the magnetic flux flowed from the rotor core into the
stator tooth number 1 through the air gap. Thus, the variance ratio
of the magnetic flux flowing in the X1-X2 induction circuit at the
moment versus time is 0, so no induced current is generated in the
close induction circuit, and no electromagnetic force is applied on
the conducting bars X1 and X2. As described above, because of the
uniformity and symmetry of the structures of the rotor and stator
in the motor, all of the other close induction circuits in the
rotor are in the same status. Since all conducting bars in the
rotor are not subject to any torque of electromagnetic force, the
rotor does not rotate.
[0033] However, during a period of changing from t=00 to t=04 via
t=02, the thing is different. In the cells in columns (2) and (3)
of the second row in FIG. 5B, the strength and direction of the
magnetomotive force generated by the positive and negative
excitation pulses corresponding to the timing t=02 in column (1)
are shown. It can be seen that the amplitude of the A phase
modulating sine wave voltage Uas is decreased at t=02 as compared
with that at t=00, the pulse width of the excitation voltage Uwb
(or the amplitude of Uma) corresponding to this is also decreased
accordingly. Therefore, the magnetic lines of force representing
the strength of the magnetomotive force of tooth number 1 and tooth
number 3 in the cells of column (2) is decreased from 4 to 3, in
which tooth number 1 has arrows directing to the rotor and is N
polarity, tooth number 3 has arrows directing to the stator yoke
and is S polarity. The amplitude of the B phase modulating sine
wave voltage Ubs is increased at t=02 as compared with that at
t=00, the pulse width of the excitation voltage Uwb (or the
amplitude of Uma) corresponding to this is also increased
accordingly. Therefore, the magnetic lines of force representing
the strength of the magnetomotive force of tooth number 2 and tooth
number 4 in the cells of column (2) is increased from 0 to 1, in
which tooth number 2 has arrow directing to the rotor and is N
polarity, tooth number 4 has arrow directing to the stator yoke and
is S polarity. If the rotor of the motor and the X1-X2 close
induction circuit thereof are still at the position of t=00, since
the excited magnetomotive force or magnetic field on the respective
stator teeth corresponding to it are changed, in the close
induction circuit X1-X2, the magnetic flux flowing from stator
teeth number 1, 2 into the rotor core through the air gap is larger
than the magnetic flux flowing from the rotor core into stator
tooth number 3 through the air gap. Therefore, it can be known from
the theory of electromagnetic induction that an induced current as
shown in the drawing is generated in the X1-X2 close circuit and
its direction is as follows: the current in the conducting bar X1
facing against stator tooth number 1 flows outward, and the current
in the conducting bar X2 facing against stator tooth number 3 flows
inward. Thus, both of the two conducting bars X1 and X2 are subject
to an electromagnetic force rightward, i.e. clockwise in relation
to the stator poles. Because of the uniformity and symmetry of the
structures of the stator and rotor in the motor, the conducting
bars in all of the other close inducting circuits in the rotor are
subject to the same electromagnetic force, thus the rotor will
rotate clockwise until a balance point of the torque is reached. At
almost the same time, in the cells shown in column (3), supposing
the width (or amplitude) of its excitation pulse is scarcely
changed, with only the direction being reversed, i.e. changed from
a positive pulse to a negative pulse, the number of the magnetic
lines of force representing the strength of the magnetomotive force
is not changed, but the direction of the magnetic lines of force
are reversed as compared with those of column (2). If the rotor and
its X1-X2 close induction circuit has reached a balance point of
the torque when the excitation voltage is a positive pulse,
obviously, there is no induced current in the close induced
circuit, and the rotor does not rotate; if the X1-X2 close
induction circuit has not reached a balance point of the torque
when the excitation voltage is a positive pulse, an induced current
opposite in direction with respect to column (2) is generated in
the X1-X2 close induction circuit. However, since the magnetomotive
force or magnetic field corresponding to the conducting bars X1, X2
is also reversed, the electromagnetic force causes the circuit to
move in the original direction, until a balance point is reached.
The situation when time goes to t=04 is shown in cells of column
(2) and column (3) of the third row in FIG. 5B. According to the
same theory, the rotor also rotates clockwise with respect to the
stator, until a new balance point of the torque is reached. So long
as the excitation phase sequence is not changed, such an
alternating pulsating rotating magnetic field, as well as the
direction of the torque of electromagnetic force generated in
respective conducting bars of the rotor, will not change.
[0034] It can be seen from FIG. 5B that when the time changes from
t=00 to t=08 in the drawing, the modulating sine wave voltages in
the excitation voltages pass 1/4 period, the conducting bars X1, X2
rotate along with the rotor of the motor from the position facing
respectively against the stator teeth number 1, 3 to the position
facing respectively against the stator teeth number 2, 4, the
number of teeth or grooves rotated by is 1. It can be concluded
that when the modulating sine wave voltages pass 1/2 period, the
number of the teeth or grooves that the rotor of the motor rotates
by is 2, i.e. a spatial angle of one pole pitch (shown as .tau. in
the drawing). When the modulating sine wave voltages pass 1 period,
the rotor of the motor rotates by exactly a spatial angle of one
pair of poles, i.e. the rotor rotates by 1/P circle. Hence, the
rotating speed per minute of such a motor can be approximately
calculated as: n=60*F1/P, which is the same as the above mentioned
rotating speed formula of the conventional induction motor.
However, for the motor, since the frequency F1 of its modulating
sine wave voltages can approach to value of "0" without limit, its
rotating speed can approach to zero without limit. It can be seen
that the rotation of the rotor can be reversed by changing any
phase of the two phases of excitation voltages into an excitation
voltage reversed from the original excitation voltage (the reversed
excitation voltage can be regarded as an excitation voltage
generated by modulating the modulating sine wave voltage of this
phase and the negative modulating square wave voltage).
[0035] Similar to the conventional induction motor, the manner
constituting the excitation windings of the present motor is not
only like this one. FIGS. 6A.about.8B show the structures of
several kinds of integral multiple pitch excitation windings in the
motor shown in FIG. 1 with Q=1, wherein FIG. 6A shows a schematic
view of A phase integral multiple pitch and single layer windings
connected to be a parallel branch circuit, and the excitation
windings in the branch circuit are connected in serial with head to
tail or tail to heads FIG. 6B is a schematic diagram of connection
of the A, B phases of integral multiple pitch and single layer
windings, wherein the number of the parallel branch circuits is
.alpha.=2, which are represented by (1) and (2) respectively. If
the terminals A2, B2 in (1) are respectively connected with the
terminals A1, B1 in (2), the number of the parallel branch circuits
of each phase can be reduced to .alpha.=1. The windings have simple
structures with each stator groove having only one coil side, which
is adaptive for a motor with lower power. FIG. 7A is a schematic
diagram of connection of the integral multiple pitch windings in
chain excited by the A phase excitation voltage, wherein each
excitation winding is connected in serial with head to head or tail
to tail, and constitutes a parallel branch circuit, i.e. .alpha.=1.
FIG. 7B is a schematic diagram of connection of the integral
multiple pitch windings in chain excited by both of A and B phases
of excitation voltages, with each stator groove having two coil
sides. In the drawing, the number of parallel branch circuits of
each phase is .alpha.=4, which are represented by (1), (2), (3),
(4) respectively. If the terminals A2, B2 in (1) are respectively
connected with the terminals A1, B1 in (2), and the terminals A2,
B2 in (3) are respectively connected with the terminals Al, B1 in
(4), the number of the parallel branch circuits of each phase can
be reduced to .alpha.=2. In the same manner, the number of the
parallel branch circuits of each phase can be reduced to
.alpha.=1.
[0036] FIG. 8A shows a schematic diagram of connection of the
integral multiple pitch wave windings excited by the A phase
excitation voltage, in which the number of the parallel branch
circuits is .alpha.=2. FIG. 8B shows a schematic diagram of
connection of the integral multiple pitch wave windings excited by
both of A and B phases of excitation voltages, in which the number
of the parallel branch circuits of each phase is still .alpha.=2,
if the excitation windings in phase are connected in serial in the
direction of the current, the number of the parallel branch
circuits of each phase can be reduced to .alpha.=1.
[0037] Since the magnetic field excited by these integral multiple
pitch excitation windings are substantially the same as that
excited by 1/2 pole pitch windings, the previous analysis to the
operational principle of the 1/2 pole pitch windings is also
applicable. The present invention does not exclude excitation
windings in other manner having equivalent functions as the
excitation windings listed above.
[0038] FIG. 9 shows a transverse sectional view of the stator and
the rotor in a three-phase switching induction motor with 24
grooves and 4 pairs of poles. In the drawing, "010" is a stator
core, "101" are stator grooves, "102" is a stator yoke, "103" are
stator teeth, "020" is a rotor having a cylindrical surface, "104"
are conducting bars, and the conducting bars and the conducting
rings (not shown in the drawings) located at the two end-faces of
the cylinder are welded to be a metal inductor like a squirrel cage
structure. "105" is a rotor core, "106" is a rotor shaft, "107" is
the air gap between the rotor and the stator, and the rotor shaft
is supported by a rotor bearing (not shown) on a machine base
connected with the stator core as a whole. It can be seen from the
drawing that, supposing Q=1, the number of phases of the excitation
voltages in the motor is M=3, and the number of stator grooves
[101] or teeth [103] is Z=24, the number of pole-pairs is
P=Z/(2*M*Q)=4, and there are eight conducting bars in the rotor,
which is twice of the number of pole-pairs.
[0039] The 24 stator teeth in FIG. 9 are grouped in the order of
number 1-24, every three adjacent teeth constitute one pole, for
example, the teeth 1, 2, 3 constitute the first pole, the teeth 4,
5, 6 constitute the second pole, the teeth 7, 8, 9 constitute the
third pole, and so on, there are totally eight poles. Every two
adjacent poles are a pair of poles, for example, the first and the
second poles constitute the first pair of poles, and the three and
the fourth poles constitute tile second pair of poles, and so on,
there are totally four pairs of poles. Since each pole includes
three stator teeth, three stator grooves and three separate
windings, they are divided into three groups according to the
spatial relative position in each pole. For example, the excitation
windings on teeth 1, 4, 7, 10, 13, 16, 19 and 22 are the first
group, the excitation windings on teeth 2, 5, 8, 11, 14, 17, 20 and
23 are the second group, and the excitation windings on teeth 3, 6,
9, 12, 15, 18, 21 and 24 are the third group, which switch into one
phase of the three phases of excitation voltages respectively.
[0040] FIG. 11 is a schematic view of the waveforms of the three
phases of pulse excitation voltages in the motor shown in FIG. 9.
In the drawing, Ur is the modulating square wave voltage, Uas, Ubs
and Ucs are three phases of modulating sine wave voltages A, B, C,
wherein Uas leads Ubs by an angle of 120.degree., Ubs leads Ucs by
an angle of 120.degree., and Ucs leads Uas by an angle of
120.degree.. It can be seen from the drawing that, the polarity
orienting principle of the pulse amplitude of the pulse width
modulated (or amplitude) modulated excitation voltages is still as
described above, that is to say, a positive value is taken when the
directions of the amplitudes of the modulating sine wave voltages
and the modulating square wave voltage are the same, and a negative
value is taken when the directions are different. Further, the
pulse amplitudes of the same phase excitation voltage are always
alternated in the positive and negative directions along the time
axis, except for the zero point of the modulating sine wave
voltage.
[0041] FIG. 10 is a stretch-out view of the 1/3 pole pitch
centralized excitation windings in the motor shown in FIG. 9, the
definitions and reference signs of the leading-in terminal for the
excitation voltages, the head ends and the tail ends of tile
excitation windings are the same as mentioned above. In the
drawing, the A phase excitation voltage Uwa (or Uma) is switched
into the excitation windings in the respective teeth in the first
group mentioned above, the C phase excitation voltage Uwc (or Umc)
is switched into the excitation windings in the respective teeth in
the second group mentioned above, and the B phase excitation
voltage Uwb (or Umb) is switched into the excitation windings in
the respective teeth in the third group mentioned above. Such a
phase sequence makes the motor shown in FIG. 9 rotate clockwise,
thus it can be referred to as clockwise excitation phase sequence.
If the phase sequences of any two phases of excitation voltages are
exchanged, for example, the three phases of pulse modulated
excitation voltages shown in FIG. 11 are respectively switched into
the excitation windings in the respective teeth in the first,
second, and third group mentioned above in a phase sequence of Uwa
(or Uma), Uwb (or Umb), and Uwc (or Umc), the motor shown in FIG. 9
will rotate anticlockwise, thus it can be referred to as
anticlockwise excitation phase sequence. In the drawing, all
antithetic windings are connected in serial to be an antithetic
branch circuit in a manner of head to head or tail to tail, and
each antithetic branch circuit acts as a parallel branch circuit.
Thus, the number of parallel branch circuits of each phase is
.alpha.=Z/2*M=4, which are represented by (1), (2), (3), (4)
respectively. If the terminals A2, C1, B2 in (1) are respectively
connected with terminals A1, C2, B1 in (2), and the terminals A2,
C1, B2 in (3) are respectively connected with terminals A1, C2, B1
in (4), the number of the parallel branch circuits of each phase
can be reduced to .alpha.=2. If the two parallel branch circuits
are further connected in serial in the same manner, the number of
parallel branch circuits of each phase can be reduced to
.alpha.=1.
[0042] FIG. 12 schematically shows the pulsating rotating magnetic
field generated when it is excited by the excitation voltages shown
in FIG. 11 in the above mentioned clockwise excitation phase
sequence, as well as the running of the motor. FIG. 12 also
comprises two parts on the left and on the right, in which the
column (1) on the left is a schematic view of the amplitudes and
phases of the A, B, C phases of the modulating sine wave voltages
Uas, Ubs, Ucs shown in FIG. 12, with the horizontal axis
representing the amplitudes of the modulating sine wave voltages,
and the vertical axis being the time axis; there are a plurality of
sub-diagrams on the right part column (2), arranged along the
vertical axis in one column. Each sub-diagram has the same
structure, and represents a part of the stretch-out view of the
cross section of the stator and rotor in the motor shown in FIG. 9
being cut along line A-A' and further dissected clockwise along the
internal surface of the stator, with the section line on the
internal surface of the stator as the horizontal axis, and its
origin of coordinate being located at the intersection point of the
line A-A' and the internal surface of the stator, so as to
schematically show, at several specific timings shown in FIG. 11,
the correspondence relation of the magnetomotive force generated at
the stator teeth and the running status of the rotor versus the
sampled amplitude values of the modulating sine wave voltages at
the timings. In order to simplify the analysis, supposing, for the
sampled values at each specific time, there is only one positive or
negative excitation pulse to correspond to it, which appears
alternatively in a time sequence as sampled. The temporal relation
between the two parts on the left and the right in the drawing is
indicated by dot lines, and the definitions of the reference signs
and expressions in the drawing is the same as those used above. It
can be seen from the drawing that, at time t=03, the conducting
bars X1, X2 are respectively located at the positions facing
against the stator teeth number 3 and number 6; at t=21, the
excitation voltages pass exactly 1/2 period, and the conducting
bars X1, X2 are rotated together with the rotor to the positions
respectively facing against the stator teeth number 6 and number 9,
i.e. a spatial angle of one pole pitch (shown as .tau. in the
drawing) is rotated by. When the modulating sine wave voltages pass
1 period, the rotor of the motor rotates by exactly a spatial angle
of one pair of poles, i.e. the rotor rotates 1/P circle. Thus, for
the three-phase motor shown in FIG. 9, the formula for the rotating
speed is the same as that of the above mentioned two-phase motor.
FIG. 13 schematically shows the pulsating rotating magnetic field
generated when it is excited by the excitation voltages shown in
FIG. 11 in the above mentioned anticlockwise excitation phase
sequence, as well as the running of the motor. It can be seen from
the drawing that, since the phase sequence of the excitation
voltages is changed, the motor rotates reversely.
[0043] FIGS. 14A.about.16B show the structures of several kinds of
integral multiple pitch excitation windings in the motor shown in
FIG. 9 with Q=1, wherein FIG. 14A shows a schematic diagram of A
phase integral multiple pitch and single layer windings connected
to be one parallel branch circuit, and the excitation windings in
the branch circuit are connected in serial in a manner of head to
tail or tail to head. FIG. 14B is a schematic diagram of connection
of the A, B, C phases of integral multiple pitch and single layer
windings, wherein the number of the parallel branch circuits is
.alpha.=2, which are represented by (1) and (2) respectively. If
the terminals A2, C1, B2 in (1) are respectively connected with the
terminals A1, C2, B1 in (2), the number of the parallel branch
circuits of each phase can be reduced to .alpha.=1. The windings
have simple structure with each stator groove having only one coil
side, which is adaptive for a motor with lower power. FIG. 15A is a
schematic diagram of connection of the integral multiple pitch
windings in chain excited by the A phase excitation voltage,
wherein each excitation winding is connected in serial in a manner
of head to head or tail to tail, and constitutes one parallel
branch circuit, i.e. .alpha.=1. FIG. 15B is a schematic diagram of
connection of the integral multiple pitch windings in chain excited
by three phases of excitation voltages A, B, C, with each stator
groove having two coil sides. In the drawing, the number of
parallel branch circuits of each phase is .alpha.=4, which are
represented by (1), (2), (3), (4) respectively. If the terminals
A2, C1, B2 in (1) are respectively connected with the terminals A1,
C2, B1 in (2), and the terminals A2, C1, B2 in (3) are respectively
connected with the terminals A1, C2, B1 in (4), the number of the
parallel branch circuits of each phase can be reduced to .alpha.=2.
In the same manner, the number of the parallel branch circuits of
each phase can be reduced to .alpha.=1. FIG. 16A is a schematic
diagram of connection of the integral multiple pitch wave windings
excited by the A phase excitation voltage, the number of parallel
branch circuits in the drawing is .alpha.=2. FIG. 16B is a
schematic diagram of connection of the integral multiple pitch wave
windings excited by three phases of excitation voltages A, B, C,
the number of parallel branch circuits of each phase in the drawing
is still 2, if the excitation windings in phase are connected in
serial in the direction of the current, the number of the parallel
branch circuits of each phase can be reduced to .alpha.=1.
[0044] FIG. 17 is a block diagram of the pulse width modulated
excitation control circuit of the motor with 24 grooves and 4 pairs
of poles as shown in FIG. 9. In the drawing, the synchronous
control pulse output by the clock signal generating unit [11] is
transmitted to the modulating square wave generating unit [12] and
frequency-converting sine wave voltage generating unit [13]
respectively. After subjecting to micro-power pulse width
modulation in pulse width modulating unit [14], the frequency
convertible three phases of modulating sine wave voltages Uas, Ubs,
Ucs with a 120.degree. phase difference with respect to one another
which are output by the frequency-converting sine wave voltage
generating unit, and the modulating square wave voltage Ur output
by the modulating square wave generating unit, are used to drive
the power switching devices in the main switching unit [16] via A,
C, B three phase driving unit [15]. The main switching unit has
three groups of DC half-bridge switching circuit made up of 6 power
field effect switching transistors and 6 capacitors. Under the
control of the driving circuit, two switching transistors in each
DC half-bridge switching circuit turn on and off alternatively, so
that three phases of pulse width modulated excitation voltages are
output from A1, A2; C1, C2; B1, B2 respectively, so as to excite
the stator windings. The power devices contained in this circuit is
fewer, the circuit of the control part can be analogous or digital,
and can be integrated to dedicated circuits, and can be deployed
within the motor together with the power device, so as to further
reduce its total size. High and low voltage DC power generating
unit [17] outputs DC high voltage required by the main switching
circuit and DC low voltage required by the integrate circuit.
[0045] FIG. 18 is a block diagram of the pulse amplitude modulated
excitation control circuit of the three-phase motor with 24 grooves
and 4 pairs of poles as shown in FIG. 7. It can be seen from the
drawing that the circuit is characterized in that: under the
control of the synchronous signal output by the clock signal
generating unit [21], the driving unit 25 is directly driven by the
modulating square voltage output by the modulating square wave
generating unit [22], the frequency-converting controlling unit
[23] synchronized by the clock signal generating unit controls the
frequency-converting sine wave voltage generating unit [24] to
output three phases of frequency convertible modulating sine wave
voltages Uas, Ubs, Ucs with sufficient power and amplitude. The
modulating sine wave voltage and the modulating square wave output
by the driving unit are subject to the amplitude modulation on
power sine wave voltage in the main switching unit [26] by three
groups of AC half-bridge switching circuits made up of 12 power
field effect switching transistors and 6 capacitors, and then three
phases of amplitude modulated excitation voltages are output from
its output terminals A1, A2; C1, C2; B1, B2 respectively. The low
voltage DC power generating unit [27] outputs DC low power to be
used in the integrate circuit.
[0046] Obviously, the excitation control on pulse width modulation
and pulse amplitude modulation in the two-phase motor with 16
grooves and 4 pairs of poles as shown in FIG. 1 can also be
achieved in the same manner as described above. The present
invention does not exclude other control circuits having equivalent
functions as described above.
[0047] It is well known that the structures and forms of
traditional switching pattern AC induction motors with the same
basic principle are not limited to a specific implementation,
neither are the switching pattern AC induction motors according to
the present invention. In FIG. 1-18, only one kind of inner rotor
motor structures is described. In fact, motors with different
structures and forms such as outer rotor type motors and disc type
motors can be manufactured by using the same principle and
technology. The following describes further embodiments of the
present invention.
[0048] FIG. 19 shows a transverse sectional view of the stator and
the rotor in a two-phase outer rotor type motor with 16 grooves and
4 pairs of poles. It can be seen that such an outer rotor type
motor is made by reversing the positions of the stator and the
rotor of an inner rotor type motor. In FIG. 19, "010" is a stator
core with a shape of column or hollow cylinder, "101" are stator
grooves penetrating along the axial direction, "102" is a stator
yoke, "103" are stator teeth distributed in an identical angle and
extending outward along a radial direction, the stator grooves and
the stator teeth are arranged alternatively surrounding the outer
surface of the stator, "020" is a rotor with a shape of hollow
cylinder, "104" are conducting bars distributed in parallel with
equal intervals along the cylindrical inner surface of the rotor
core of the motor, the conducting bars and the conducting rings
(not shown) located at the two end-surfaces of the cylinder are
welded to be a metal inductor like a squirrel cage structure, "105"
is a rotor core, "107" is the air gap between the stator and the
rotor, and the rotor rotates along the cylindrical outer surface of
the stator core with the support of a shaft (not shown) connected
with the rotor. The number Z of the stator grooves or teeth is
still determined by the following equation: Z=2*M*P*Q, wherein M
being the number of phases of the excitation voltages, P being the
number of pairs of the stator poles, Q being the number of the
grooves or teeth per pole per phase, and the number K of the
parallel conducting bars of the metal inductor in the rotor
"squirrel cage" of the motor being twice of the number P of pairs
of the stator poles, i.e. K=2*P*Q. When the number Z of the stator
grooves or teeth is fixed, if the number of the stator grooves or
teeth per pole per phase is Q=1, the number of the pole-pairs and
the number of the conducting bars corresponding thereto in the
rotor can be increased to obtain a larger output torque. In the
embodiment shown in FIG. 19, since the number of the phases of the
excitation voltages is M=2, and the number of the stator grooves
[101] or teeth [103] is Z=16, when Q=1, the number of pole-pairs is
P=Z/(2*M*Q)=4, and there are 8 conducting bars in the rotor, which
are twice of the number of pole-pairs.
[0049] FIG. 20 shows a transverse sectional view of the stator and
the rotor in a three-phase outer rotor type switching pattern
induction motor with 24 grooves and 4 pairs of poles, wherein "010"
is a stator core with a shape of cylinder or column, "101" are
stator grooves, "102" is a stator yoke, "103" are stator teeth,
"020" is a rotor with a shape of cylinder, "104" are conducting
bars, the conducting bars and the conducting rings (not shown)
located at the two end-surfaces of the cylinder are welded to be a
metal inductor like a squirrel cage structure, "105" is a rotor
core, "107" is the air gap between the stator and the rotor, and
the rotor rotates along the cylindrical outer surface of the stator
core with the support of a shaft (not shown) connected with the
rotor. It can be seen that, given Q=1, the number of the phases of
the excitation voltages of the motor is M=3, the number of the
stator grooves [101] or teeth [103] is Z=24, the number of
pole-pairs is P=Z/(2*M*Q)=4, and there are 8 conducting bars in the
rotor, which are twice of 4 pole-pairs.
[0050] FIG. 21A shows the three-dimension solid schematic diagram
of the stator core and the rotor core of a three-phase disk type
motor with 48 grooves and 8 pairs of poles, wherein "010" is a
ring-shaped stator core with a shape of disk, "101" are stator
grooves, "102" is a stator yoke, "103" are stator teeth and the
plan view of the stator grooves is shown as FIG. 21B1. "020" is a
ring-shaped rotor core with a shape of disk, the conducting bars
"104" are located in the rotor grooves, and welded with two
conducting end-rings "108" and "109" respectively located at the
inner ring surface and the outer ring surface of the ring-shaped
stator core, and the conducting bars "104" and conducting end-rings
"108" and "109" form a squirrel cage type metal conductor with a
disc type structure, whose plane view is shown as FIG. 21B2. It can
be seen that the number of grooves or teeth per pole per phase is
Q=1, the number of the phases of the excitation voltages of the
motor is M=3, the number of the stator grooves [101] or teeth [103]
is Z=48, the number of pole-pairs is P=Z/(2*M*Q)=8, and there are
16 conducting bars in the rotor, which are twice of 8 pole-pairs.
If the stator core and the rotor core of this three-phase disk type
motor are sectioned along the line A-A' in the drawing, it may be
found that the structures of the stator and the rotor, as well as
the function and the principle of exciting the excitation windings
of the rotor to form a rotating magnetic field, are the same as
those of the cylindrical motor. Therefore, the winding structure
and the exciting manner of the disk type motor are entirely
identical with those of the cylindrical motor.
[0051] FIG. 21C is a transverse sectional view of a disk type
motor, wherein "301" are disk-shaped stators, "302" is a
disk-shaped rotor, "303" are excitation windings. "304" is a shaft
connected with the rotor, "305" is a bearing, and "306" is a
housing. It can be seen that this kind of disk type motor is
disposed with two stators and one rotor in the middle along the
axial direction, wherein in fact the rotor is made by two
back-to-back rotors, whereby there are two air gaps "307", and the
disk type motor has a higher power density compared with the
cylindrical motor. Meanwhile, since the disk type motor has reduced
the axial size, the motor torque can be increased by properly
enlarging the radial size. To meet different needs, this kind of
disc type motor can be formed by either one stator and one rotor,
or more stators and more rotors.
[0052] The exciting manner of the stator excitation windings is the
same as those in FIGS. 1-18, i.e. switching AC pulse excitation
technique, wherein the excitation voltages are two-phase continuous
sine wave voltage with phase difference of 90.degree. or
three-phase continuous sine voltage wave with phase difference of
120.degree. with equal virtual values and frequencies, which can be
referred to as modulating sine voltages, and a pulse square wave
voltage within the frequency range of voice or ultrasonic, which
can be referred to as a modulating square wave voltage, as well as
a pulse modulating voltage generated by performing pulse width
modulation or pulse amplitude modulation, which can be referred to
as a sine wave pulse modulating excitation voltage.
[0053] The most essential innovation of the novel motor according
to the present invention is the innovation of the excitation
technique, i.e. it is excited by sine wave pulse modulated voltages
within the frequency range of voice or ultrasonic, when the
excitation windings in the stator are excited, the required
pulsating alternating rotating magnetic field is generated in the
air gap between the stator and the rotor, induced current is
generated in the conducting bars on the rotor, and the torque of
electromagnetic force in such a pulsating alternating rotating
magnetic field is applied on the conducting bars, so that the rotor
of the motor rotates. Supposing the frequency of the modulating
sine wave voltages is F1, the frequency of the modulating square
wave voltage is F2, when the motor operates, the rotating speed of
the pulsating alternating rotating magnetic field only depends on
the frequency F1 of the modulating sine wave voltages, and is
independent of the frequency F2 of the modulating square wave
voltage, thereby the speed regulation of the motor can be achieved
by changing the frequency F1 of the modulating sine wave voltage
with a control circuit. Since the pulse frequency of the sine wave
pulse modulated excitation voltage, i.e. the pulsating alternating
frequency of the rotating magnetic field, equals to the frequency
F2 of the modulating square wave voltage with its value within the
frequency range of voice or ultrasonic, which is much greater than
the frequency F1 of the modulating sine wave voltages, the
resistance of the excitation windings of the motor is proportional
to frequency F2, and is independent of frequency F1 of the
modulating sine wave voltages. The higher F2 is, the smaller the
size and mass of the stator core, the rotor core and the windings
of the motor are.
[0054] The cores of the stator and the rotor, such as the cores of
the stator and the rotor of the outer rotor type motor, are made by
soft magnetic material laminations which meet corresponding
frequency characteristics within the frequency range of voice and
ultrasonic, which are subject to surface insulation treatment, and
then to piling along the axial direction, and it can also be made
of ferrite materials with corresponding frequency characteristic as
a whole or in a manner of sectioning along the axial direction.
[0055] The stator core and the rotor core of the disk type motor
can be made by belt-shaped soft magnetic materials which are
subject to surface insulation treatment, and then wrapped along the
axial direction to form a shape of disk, the belt-width being the
thickness of the disk-type rotor or stator core, and treated along
the radial direction to form grooves and teeth, or it can also be
made of ferrite materials with corresponding frequency
characteristic as a whole.
[0056] The same as FIGS. 1-18, when the number of the grooves or
teeth per pole per phase is Q=1, the structure of the stator
excitation windings adopts centralized windings with 1/M pole pitch
or integral pitch. When the number of the grooves or teeth per pole
per phase is Q>1, the distributed windings are adopted. The
structure manner of the excitation windings are the same as those
described in FIGS. 1-18.
[0057] Therefore, the operating principle of the outer rotor type
motor and the disk type motor, and the circuit structure of the
excitation voltages are the same as those in FIGS. 1-18.
* * * * *