U.S. patent application number 13/363028 was filed with the patent office on 2012-10-11 for control unit for an electric motor, in particular for a fan motor.
This patent application is currently assigned to Papst Licensing GmbH & Co. KG. Invention is credited to Andras Lelkes.
Application Number | 20120256576 13/363028 |
Document ID | / |
Family ID | 36710335 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120256576 |
Kind Code |
A1 |
Lelkes; Andras |
October 11, 2012 |
Control Unit For An Electric Motor, In Particular For A Fan
Motor
Abstract
The invention provides a control unit for at least one electric
motor, wherein the control unit performs open-loop or closed-loop
control of the motor speed of the electric motor in such a way that
in the case of control values in specific ranges which are typical
of a fault when the setpoint value is being predefined, such a
fault being, for example, a line break, a voltage failure or a
short circuit, the control unit drives the motor with a predefined
setpoint value which differs from the current control value.
Inventors: |
Lelkes; Andras; (Bad
Durrheim, DE) |
Assignee: |
Papst Licensing GmbH & Co.
KG
St Georgen
DE
|
Family ID: |
36710335 |
Appl. No.: |
13/363028 |
Filed: |
January 31, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12299425 |
Nov 3, 2008 |
|
|
|
13363028 |
|
|
|
|
Current U.S.
Class: |
318/400.42 |
Current CPC
Class: |
H02P 29/02 20130101;
H02P 6/08 20130101; H02P 6/12 20130101 |
Class at
Publication: |
318/400.42 |
International
Class: |
H02P 6/08 20060101
H02P006/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2006 |
DE |
20 2006007136.9 |
May 3, 2007 |
WO |
PCTEP2007054301 |
Claims
1-14. (canceled)
15. A cooling fan, comprising: a housing; a brushless DC motor
mounted in the housing; a fan wheel operatively engaged with a
rotor of the brushless DC motor, wherein the fan wheel is adapted
to rotate when the brushless DC motor is operated in order to
create a flow of cooling air; a motor controller mounted in the
housing in a fixed relationship with the brushless DC motor,
wherein the motor controller is adapted (a) to cause the rotor and
the fan wheel to rotate at a nonzero speed if the magnitude of a
control signal is in a range of values associated with a fault
condition and (b) to stop rotation of the rotor and the fan wheel
if the control signal is between a nonzero first threshold value
and a second threshold value greater than the first threshold
value.
16. The cooling fan of claim 15, wherein the range of values
associated with the fault condition is a range from zero to the
first threshold value.
17. The cooling fan of claim 15, wherein the control signal is one
of a pulse-width modulated signal and a voltage.
18. The cooling fan of claim 15, wherein control signal is an
analog voltage signal.
19. The cooling fan of claim 18, wherein the range of values
associated with a fault condition includes a value that represents
one of zero volts and a voltage identical to a supply voltage.
20. The cooling fan of claim 15, wherein the control signal is a
modulated signal and the range of values associated with a fault
includes a value associated with a signal modulated 0% and a value
associated with a signal modulated 100%.
21. The cooling fan of claim 15, comprising an analog-to-digital
converter adapted to convert an analog control signal into a
digital control signal.
22. The cooling fan of claim 15, wherein the first threshold value
is one of 0.5 volts and 5% modulation.
23. The cooling fan of claim 22, wherein the second threshold value
is one of 1 volt and 10% modulation.
24. The cooling fan of claim 23, comprising a further circuit to
generate a warning signal if the control value indicates a
fault.
25. The cooling fan of claim 24, wherein the further circuit
generates one of a visual warning signal, an audible warning
signal, and a combination thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation of U.S. patent
application Ser. No. 12/299,426, which was filed on Nov. 30, 2008,
and is the U.S. National Stage of International Patent Application
No. PCT/EP2007/054301, filed on May 3, 2007, which in turn claims
priority to German Patent Application No. 20 2006 007 136.9, filed
May 4, 2006. The entire text of all of the above-listed
applications are hereby incorporated herein by reference in their
entireties.
DESCRIPTION
[0002] The invention relates to a control unit for an electric
motor. Such control units are used to perform open-loop or
closed-loop control of the motor speed. In many cases, in
particular in fan applications, the motor speed is lowered
according to demand in order to reduce the consumption of electric
power. In the case of a fan, not only the power demand but also the
flow noise are highly dependent on the motor speed. Referring to
FIG. 8A and FIG. 1, FIG. 1 shows the shaft power output (1) of the
fan motor 100 and the flow noise (2) of the fan 106 as a function
of the motor speed. The torque demand of a fan wheel 106 increases
to the power of two of the motor speed. As a result, the shaft
power output of the motor 100 even increases to the power of three
of the motor speed. This means that, for example, at half the motor
speed the output power of the motor 100 only reaches 12.5% of the
rated power. The shaft power output even drops below 1% if the
motor speed is less than 21.5% of the rated motor speed. The flow
noise (2) has been found empirically to drop to 15-17 dB(A) when
the motor speed is halved.
[0003] In addition to the energy demand, the noise can therefore
also be significantly reduced if motor-speed-controlled fan motors
are used and if open-loop control of the motor speed and therefore
of the air line is performed according to demand. The motor speed
of a fan can be influenced in different ways as a function of the
types of motor used. In the case of direct current motors,
open-loop control of the motor speed is performed by means of the
motor voltage. The control unit can predefine the motor voltage
with a clocked voltage converter (chopper) or by means of a
controlled rectifier. For universal motors, the amplitude of the
alternating voltage can be set by means of a phase angle
controller. In the case of a brushless motor (also referred to as
BLDC or electronically commutated motor, referred to as EC motor),
the control unit performs the electronic commutation. The control
unit can additionally influence the motor voltage and as a result
the motor speed through corresponding clocking of the transistors
in the commutation electronics. In the case of asynchronous motors,
either the frequency and the amplitude of the motor voltage are
predefined with a frequency converter, or in the case of
cost-effective systems, in particular in the case of fan drives,
only the motor voltage is changed, for example, by means of a phase
angle controller (referred to as slip controller).
[0004] The desired motor speed is usually defined by means of
superimposed open-loop control. The setpoint value of the motor
speed is often transmitted with an analogue value (for example 0-10
V) or with a pulse-width-modulated, digital value (PWM). FIG. 2
shows an input characteristic which is typical of fan applications.
In this example, the superimposed controller has to output 0-10% of
the control signal (x) for the motor to be stationary (nsetp=0). A
disadvantage of this method is that in the case of faults, for
example in the case of a line break or a short circuit in the
control line, the fan can stop. In this case, it is not possible to
ensure sufficient cooling, which may lead to a failure of the
system. As a result, considerable material damage may occur and
large losses due to a failure of production.
SUMMARY OF THE INVENTION
[0005] The present invention is therefore based on the object of
configuring the input characteristic of the control unit in such a
way that in the case of such a fault the motor continues to operate
with a predefined motor speed. In the case of a fault such as a
line break or a short circuit in the control line or in the case of
the failure of the superimposed controller, the probability is high
that the control signal x will record the value 0% or 100%.
[0006] According to the invention, the customary input
characteristic is therefore changed according to FIG. 2 in such a
way that in the case of input values in specific ranges, primarily
approximately 0% or 100%, the controller drives the motor with a
predefined setpoint value which differs from the current setpoint
value.
[0007] In one advantageous embodiment, the controller additionally
outputs a warning in the case of such a fault. This warning can be
output by means of a visual or audible signal, by means of an
analogue or digital electronic signal or by means of a commutation
bus, for example, CAN bus.
BRIEF SUMMARY OF THE DRAWINGS
[0008] In the figures:
[0009] FIG. 1 shows the shaft output power of the fan motor and the
flow noise of the fan as a function of the motor speed;
[0010] FIG. 2 shows an input characteristic which is typical of fan
applications;
[0011] FIG. 3 shows the input characteristic of the control unit in
an advantageous embodiment;
[0012] FIG. 4 shows the inventive input characteristic of the
control unit if a setpoint value of nsetp=75% is used when such a
fault is detected;
[0013] FIG. 5 shows the program sequence for implementing the input
characteristic curve;
[0014] FIG. 6 shows a exemplary circuit;
[0015] FIG. 7 shows a further exemplary circuit with a warning
output;
[0016] FIG. 8A is an isometric view of a fan that may be operated
by a motor controlled by a control unit in accordance with present
invention; and
[0017] FIG. 8B is an isometric view of a pump that may be operated
by a motor controlled by a control unit in accordance with present
with present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 3 shows the input characteristic of the control unit in
an advantageous embodiment. In this example, the superimposed
controller must output 5-10% of the control signal (x) instead of
0-10% in order to stop the motor. In the case of an analogue
control signal (0-10 V) this means that in the case of a control
voltage of 0.5 V to 1 V the motor is stationary (nsetp=0). A
control voltage of less than 0.5 V indicates a fault (for example a
failure of the superimposed controller, a line break or a short
circuit in the control line). When a setpoint value is predefined
with a PWM controlled digital signal, the motor will be stationary
given a control signal of 5 to 10% PWM. A PWM factor of less than
5% means a fault. This is the case, for example, if the control
signal is continuously at a low level (corresponds to 0% PWM). In
this case, a predefined setpoint value of the motor speed is used.
In FIG. 3, this value is for the fault nsetp=100%. For applications
such as, for example, with fans, reliable operation is therefore
ensured even in the case of a fault in the transferring of setpoint
values. Although in fan applications, the power and noise are not
reduced when such a fault occurs, sufficient cooling is
ensured.
[0019] A setpoint value which differs from the maximum (100%)
setpoint value of the motor speed can also be used in the event of
a fault. In some cases, a reduced motor speed is sufficient for
cooling in a normal situation, and the maximum motor speed (100%)
is provided only for specific exceptional situations, for example
for the failure of one of the fans which operate in parallel. FIG.
4 shows the inventive input characteristic of the control unit if a
setpoint value of nsetp=75% is used for the detected fault. This
value is therefore used if the control signal assumes x values in
the ranges 0-5% and 95%-400%.
[0020] In order to implement an input characteristic curve
according to FIG. 4, the analogue control signal can firstly be
converted into a digital value using an analogue/digital converter.
The signal is then further processed in digital form. In one
advantageous refinement of the invention, this can be carried out
by means of a programmable component such as a microprocessor,
digital signal processor (DSP) or microcontroller. The programme
sequence for implementing the input characteristic curve is
illustrated in FIG. 5.
[0021] In a further refinement of the invention, the input
characteristic curve is implemented using an electronic analogue
circuit. FIG. 6 shows an exemplary circuit for this. This circuit
is composed of four analogue comparators (K1 to K4), two
operational amplifiers (V1, V2), two digital NAND gates, and of an
analogue multiplexer (MUX). The comparators compare the control
signal X with the voltage values at the discontinuities in the
input characteristic according to FIG. 4, that is to say with 0.5
V, 1 V, 9 V and 9.5 V. These voltages are produced here from the 10
V supply voltage with a resistor series. The output signals of the
comparators are further processed with the NAND gates and control
the analogue multiplexer, as is shown by the following table.
TABLE-US-00001 Control signal X K4 K3 K2 K1 Al AO Y 0 . . . 0.5 V 1
1 F 0.5 . . . 1 V 1 0 0 V 1 . . . 9 V 0 0 9X - 1V/8 9 . . . 9.5 V 0
1 10 V 9.5 . . . 10 V 0 0 1 1 1 1 F
[0022] F is here the predefined setpoint value for the fault. If
this value is, for example, 75%, as in FIG. 4, 7.5 V has to be
connected here.
[0023] This circuit can be supplemented with a warning output (W),
as illustrated in FIG. 7. In a normal situation this output
supplies a logic "1" and in the case of a fault it supplies a logic
"0". This warning is output if the control signal X assumes values
lower than 0.5 V or higher than 9.5 V.
[0024] Referring to FIGS. 8A and 8B, the control unit 102 according
to the invention can form a separate unit or can be integrated into
the motor housing or into the terminal box of the motor 100 so that
motor 100 and control unit 102 form one mechanical unit. The
solution according to the invention can also advantageously be used
in compact fans where control unit 102 and motor 100 are integrated
parts of the compact fan. The solution according to the invention
can, however, be used not only in fans, blowers and pumps 108 but
also in any application in which in the event of a fault it is more
favourable to operate the motor 100 with a predefined motor speed
than to switch off the motor 100. Correspondingly, the invention is
not only limited to the illustrated and described exemplary
embodiments but rather also comprises all embodiments of like
effect within the sense of the invention.
[0025] As one example, a brushless DC motor that incorporates
aspects of the invention disclosed herein can be used to spin one
or more hard disks in operative relation to at least one read/write
head inside of a clean room environment that is manufactured to HDD
industry contamination standards. As another example, the motors
disclosed herein can be used to move storage media in other
information storage devices such as, for example, an optical disk
drive, a magneto-optical disk drive, a tape drive or a VCR.
* * * * *