U.S. patent application number 11/109743 was filed with the patent office on 2005-12-08 for reciprocating compressor, driving unit and control method for the same.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Chang, Keun Sik, Chang, Phil Soo.
Application Number | 20050271526 11/109743 |
Document ID | / |
Family ID | 34939524 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050271526 |
Kind Code |
A1 |
Chang, Keun Sik ; et
al. |
December 8, 2005 |
Reciprocating compressor, driving unit and control method for the
same
Abstract
A driving unit and control method for a reciprocating compressor
for controlling a frequency of input power so that an operational
frequency of the compressor follows a resonant frequency, which
varies depending on a variation of the load applied to the
compressor. The reciprocating compressor includes an inverter to
adjust the frequency of the input power, so that the frequency of
the input power is set at a value corresponding to the resonant
frequency by the inverter. The resonant frequency is set in a range
of 60% to 90% of the normal power frequency. The compressor further
includes a controller to control the frequency of the input power
so that the operational frequency of the compressor follows the
resonant frequency, which varies depending on the operation of the
compressor.
Inventors: |
Chang, Keun Sik; (Suwon-si,
KR) ; Chang, Phil Soo; (Seongnam-Si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
34939524 |
Appl. No.: |
11/109743 |
Filed: |
April 20, 2005 |
Current U.S.
Class: |
417/417 ;
417/415; 417/416; 417/44.1; 417/44.11 |
Current CPC
Class: |
F04B 2203/0401 20130101;
F04B 2201/0806 20130101; F04B 2203/0402 20130101; F04B 35/045
20130101; F04B 2203/0404 20130101 |
Class at
Publication: |
417/417 ;
417/415; 417/416; 417/044.1; 417/044.11 |
International
Class: |
F04B 017/00; F04B
049/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2004 |
KR |
10-2004-0040994 |
Sep 13, 2004 |
KR |
10-2004-0073172 |
Claims
What is claimed is:
1. A reciprocating compressor comprising: an inverter to receive a
power and adjust a frequency of the received power and to input the
adjusted power to the compressor, wherein: a resonant frequency of
the compressor is less than a typical frequency of the received
power, and a frequency of the input power corresponds to the
resonant frequency.
2. The compressor according to claim 1, wherein the resonant
frequency is between 60% to 90% of the typical frequency of the
received power.
3. The compressor according to claim 2, further comprising: a
controller to control an operation of the compressor, wherein the
controller controls the frequency of the input power so that an
operational frequency of the compressor follows the resonant
frequency as the resonant frequency varies depending on the
operation of the compressor.
4. The compressor according to claim 3, wherein the controller
determines a phase difference between the frequency of the input
power and the operational frequency of the compressor, thereby
controlling the inverter to increase or decrease the frequency of
the input power according to a correction value corresponding to
the phase difference.
5. The compressor according to claim 4, further comprising: a
piston mounted in the compressor; a current detector to detect the
frequency of the input power; and a displacement detector to detect
a displacement of the piston to determine the operational
frequency.
6. The compressor according to claim 5, further comprising: a load
detector to detect a load applied to the compressor wherein the
controller controls the inverter so that the frequency of the input
power is equal to the resonant frequency when the load detected by
the load detector is a normal load, and the frequency of the input
power is greater than the resonant frequency when the detected load
is higher than the normal load.
7. A reciprocating compressor comprising: an inverter to adjust a
frequency of power input to the compressor; and a controller to
control the inverter so that an operational frequency of the
compressor coincides with the frequency of the input power
according to a determined phase difference between the operational
frequency and the frequency of the input power.
8. The compressor according to claim 7, wherein the controller
controls the inverter to increase or decrease the frequency of the
input power according to a correction value corresponding to the
phase difference, thereby allowing the operational frequency to
follow a resonant frequency of the compressor which varies
depending on an operation of the compressor.
9. A driving unit for driving a reciprocating compressor,
comprising: an inverter to adjust a frequency of input power to be
applied to the compressor; a load detector to determine a load
applied to the compressor; and a controller to control the inverter
so that the frequency of the input power is equal to a resonant
frequency of the compressor when the load determined by the load
detector is a normal load, whereas the frequency of the input power
is greater than the resonant frequency when the determined load is
greater than the normal load.
10. A driving unit for driving a reciprocating compressor,
comprising: a piston; an inverter to adjust a frequency of input
power to be applied to the compressor; a current detector to detect
the frequency of the input power; a displacement detector to detect
a displacement of the piston to thereby determine an operational
frequency of the compressor; and a controller to control the
inverter to thereby determine a phase difference between the
operational frequency and the frequency of the input power and then
increase or decrease the frequency of the input power based on the
determined phase difference, wherein the operational frequency
follows a resonant frequency, which varies depending on an
operation of the compressor.
11. A control method for a reciprocating compressor comprising:
determining whether a load applied to the compressor is a high load
or normal load; applying a power, having a frequency equal to a
resonant frequency of the compressor, to the compressor if the load
applied to the compressor is the normal load; and applying a power,
having a frequency greater than the resonant frequency of the
compressor, to the compressor if the load applied to the compressor
is the high load.
12. A control method for a reciprocating compressor having an
inverter, comprising: determining a phase difference between a
frequency of input power and an operational frequency of the
compressor; and controlling the inverter to increase or decrease
the frequency of the input power with a correction value
corresponding to the phase difference.
13. The compressor according to claim 4, wherein the controller
maintains the frequency of the input power when the determined
phase difference is zero.
14. The compressor according to claim 5, wherein the resonant
frequency varies according to a gas pressure acting on the
piston.
15. A control method for a reciprocating compressor: inputting a
power having a frequency greater than a resonant frequency of the
compressor; adjusting the input power to the resonant frequency of
the compressor; and driving the compressor with the adjusted power.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2004-40994, filed on Jun. 4, 2004 in the Korean
Intellectual Property Office and Korean Patent Application No.
2004-73172, filed on Sep. 13, 2004 in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a reciprocating compressor,
and more particularly, to a driving unit and control method for a
reciprocating compressor for controlling a frequency of input power
so that an operational frequency of the compressor is a resonant
frequency which varies based on a variation of load applied to the
compressor, and also for improving efficiency of the reciprocating
compressor in a low load state.
[0004] 2. Description of the Related Art
[0005] In general, compressors are used in air conditioning
systems, refrigerators, etc. to compress a refrigerant. One type of
compressor is a reciprocating compressor, which compresses the
refrigerant by making use of variation in the volume of a
compressing chamber caused by reciprocating movements of a piston.
Certain reciprocating compressors employ a rotary motor as a
driving unit, and others employ a conventional linear motor.
[0006] The reciprocating compressors employing the conventional
linear motor are configured such that the piston, which
reciprocates in the compressing chamber, is directly connected to a
rectilinearly-reciprocati- ng mover of the linear motor and is
supported by an elastic resonant spring. In such a reciprocating
compressor, the compression of the refrigerant is achieved as the
mover rectilinearly reciprocates in correspondence with a frequency
of input power when an alternating current is applied to the linear
motor. The piston reciprocates in accordance with the rectilinear
reciprocation of the mover. Here, the resonant spring achieves an
exciting force which facilitates the movement of the piston and
thus ensures smooth reciprocating motion of the piston.
[0007] The motion of the piston increases when operational
efficiency of the piston coincides with the resonant frequency
(i.e. natural frequency) of the compressors. Therefore, there have
been attempts to make the resonant frequency of the compressors
coincide with a typical power frequency for the purpose of
improving the efficiency of the compressors. That is, in order to
improve compression capability of the compressors, it is important
to adjust the resonant frequency of the compressors to correspond
to the typical power frequency. Such an adjustment of the resonant
frequency of the compressors can be achieved through control of the
mass of the moving units, including the piston and the mover of the
linear motor, as well as controlling an elasticity of the resonant
spring.
[0008] However, in conventional reciprocating compressors which are
controlled to have the resonant frequency equal to the power
frequency, the typical power having a high frequency (i.e., the
conventional 60 Hz) must be used as an input power, resulting in an
acceleration in an operational speed of the compressors. This makes
it difficult to expand the available range of compression
capabilities of the compressors and thus limits the operation of
the compressors to a relatively low frequency range, and also
results in reduced efficiency of the compressors due to motor core
loss and mechanical friction loss.
[0009] Further, the conventional reciprocating compressors may
experience a variation in resonant frequency due to a gas pressure
variation acting on the piston when a load varies during operation
of the compressors. Such a variation of the resonant frequency
leads to an inconsistency between the resonant frequency and the
operational frequency, resulting in a deterioration in the
efficiency of the compressors.
SUMMARY OF THE INVENTION
[0010] Accordingly, it is an aspect of the present invention to
provide a driving unit and control method for a reciprocating
compressor for setting a resonant frequency of the compressor at a
value less than a frequency of the typical power and making a
frequency of input power to be applied to the compressor coincide
with the resonant frequency, thereby being capable of expanding.
Thus, the available range of compression capabilities of the
compressor allows the compressor to resonate in a low frequency
range which is less than the frequency of the typical power,
resulting in an improvement in efficiency of the compressor.
[0011] It is another aspect of the present invention to provide a
driving unit and control method for a reciprocating compressor for
allowing an operational frequency of the compressor to coincide
with a varying resonant frequency based on a variation of load
applied to the compressor, thereby improving efficiency of the
compressor.
[0012] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be apparent from the description, or may be learned by
practice of the invention.
[0013] The forgoing and/or other aspects may be achieved by
providing a reciprocating compressor including an inverter to
receive a power and adjust a frequency of the received power and to
input the adjusted power to the compressor, wherein: a resonant
frequency of the compressor is less than a typical frequency of the
received power, and a frequency of the input power corresponds to
the resonant frequency.
[0014] The resonant frequency may be between 60% and 90% of the
typical frequency of the power.
[0015] The compressor may further include a controller to control
operation of the compressor, and the controller may control the
frequency of the input power so that an operational frequency of
the compressor follows the resonant frequency as the resonant
frequency varies depending on the operation of the compressor.
[0016] The controller may determine a phase difference between the
frequency of the input power and the operational frequency of the
compressor, thereby controlling the inverter to increase or
decrease the frequency of the input power according to a correction
value corresponding to the phase difference.
[0017] The compressor may further include a current detector to
detect the frequency of the input power applied from the inverter
to the compressor; and a displacement detector to detect
displacement of a piston mounted in the compressor so as to
determine the operational frequency.
[0018] The compressor may further include a load detector to detect
a load applied to the compressor; the controller may control the
inverter so that the frequency of the input power is equal to the
resonant frequency when the load detected by the load detector is a
normal load, and the frequency of the input power is greater than
the resonant frequency when the detected load is a higher than the
normal load.
[0019] The forgoing and/or other aspects are achieved by providing
a reciprocating compressor an inverter to adjust a frequency of
power input to the compressor including: and a controller to
control the inverter so that an operational frequency of the
compressor coincides with the frequency of the input power
according to a determined phase difference between the operational
frequency and the frequency of the input power.
[0020] The forgoing and/or other aspects are achieved by providing
a driving unit for driving a reciprocating compressor including: an
inverter to adjust a frequency of input power to be applied to the
compressor; a load detector to determine a load applied to the
compressor; and a controller to control the inverter so that the
frequency of the input power is equal to a resonant frequency of
the compressor when the load determined by the load detector is a
normal load, whereas the frequency of the input power is greater
than the resonant frequency when the determined load is greater
than the normal load.
[0021] The forgoing and/or other aspects are achieved by providing
a driving unit for driving a reciprocating compressor including: a
piston; an inverter to adjust a frequency of input power to be
applied to the compressor; a current detector to detect the
frequency of the input power; a displacement detector to detect a
displacement of the piston to thereby determine an operational
frequency of the compressor; and a controller to control the
inverter to thereby determine a phase difference between the
operational frequency and the frequency of the input power and then
increase or decrease the frequency of the input power based on the
determined phase difference, wherein the operational frequency
follows a resonant frequency, which varies depending on an
operation of the compressor.
[0022] The forgoing and/or other aspects are achieved by providing
a control method for a reciprocating compressor including:
determining whether a load applied to the compressor is a high load
or normal load; applying a power, having a frequency equal to a
resonant frequency of the compressor, to the compressor if the load
applied to the compressor is the normal load; and applying a power,
having a frequency greater than the resonant frequency of the
compressor, to the compressor if the load applied to the compressor
is the high load.
[0023] The forgoing and/or other aspects are achieved by providing
a control method for a reciprocating compressor having an inverter,
including: determining a phase difference between a frequency of
input power and an operational frequency of the compressor; and
controlling the inverter to increase or decrease the frequency of
the input power with a correction value corresponding to the phase
difference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] These and/or other aspects and advantages of the invention
will become apparent and more easily appreciated from the following
description of the embodiments, taken in conjunction with the
accompanying drawings of which:
[0025] FIG. 1 is a sectional view of a reciprocating compressor in
accordance with an embodiment of the present invention;
[0026] FIG. 2 is a control block diagram of a driving unit provided
in the reciprocating compressor of FIG. 1; and
[0027] FIG. 3 is a flow chart illustrating a control method for the
reciprocating compressor of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Reference will now be made in detail to the embodiment of
the present invention, an example of which is illustrated in the
accompanying drawings, wherein like reference numerals refer to
like elements throughout. The embodiment is described below to
explain the present invention by referring to the figures.
[0029] FIG. 1 is a sectional view of a reciprocating compressor in
accordance with an embodiment of the present invention. As shown in
FIG. 1, the reciprocating compressor includes a hermetically sealed
container 10 formed by coupling an upper container 10a and a lower
container 10b. The reciprocating compressor further includes: a
compression unit 20 having a cylinder block 21, a piston 22 and a
cylinder head 23; and a linear motor 30. The linear motor 30 drives
the compression unit 20 and has a mover 31 and inner and outer
stators 32 and 33. The compression unit 20 and the linear motor 30
are mounted as a set in the hermetically sealed container 10.
[0030] The cylinder block 21 of the compression unit 20 includes: a
cylinder portion 21a internally defining a compressing chamber 24
and a supporting portion 21b radially extending from the outer
circumference of a lower region of the cylinder portion 21a to
support the outer stator 33 thereon. The cylinder block 21 is
supported, at a lower end of the supporting portion 21b thereof, by
means of a plurality of damping members 25, so that the cylinder
block 21 is spaced apart from an inner wall surface of the lower
container 10b.
[0031] The piston 22 is mounted in the compressing chamber 24 of
the cylinder block 21 in a vertically reciprocable manner. The
cylinder head 23 is located under the cylinder block 21 and
internally defines an introducing chamber 23a and a discharge
chamber 23b. At the introducing chamber 23a of the cylinder head 23
is formed an introducing port 23c containing an introducing valve
plate, and at the discharge chamber 23b of the cylinder head 23 is
formed a discharge port 23d containing a discharge valve plate.
Reference numeral 11 designates an outer introducing pipe,
reference numeral 12 designates an introducing pipe connected to
the introducing chamber 23a, and reference numeral 13 designates a
discharge pipe connected to the discharge chamber 23b so as to
extend to the outside of the hermetically sealed container 10.
[0032] The linear motor 30, adapted to actuate the piston 22, is
mounted so that the mover 31 is located inside of the cylinder
portion 21a and the inner and outer stators 32 and 33 are located
outside of the cylinder portion 21a. The mover 31 has a hollow
cylindrical form so that an upper fixing portion 31a thereof is
coupled to the outer circumference of an upper region of the piston
22, thereby allowing the mover 31 to vertically reciprocate along
with the piston 22. The mover 31 has a magnet 35 attached to a
lower end of the upper fixing portion 31a. The magnet 35 allows the
mover 31 to vertically reciprocate through an interaction between
the magnet 35 and the outer stator 33.
[0033] Both the inner stator 32 and the outer stator 33 have a
cylindrical form and are located, respectively, inside and outside
of the mover 31. The inner stator 32 is fixed to the outer
circumference of the cylinder portion 21a and guides the vertical
reciprocation of the mover 31 and ensures smooth flow of magnetic
flux through the magnet 35 of the mover 31. The outer stator 33 has
an exciting coil 34 to electromagnetically interact with the magnet
35. A lower end of the outer stator 33 is supported on the
supporting portion 21b of the cylinder block 21 and an upper end of
the outer stator 33 is supported by a fixing frame 36.
[0034] The reciprocating compressor further includes a resonant
spring 37 in the form of a multi-layered plate spring. The resonant
spring 37 is mounted on the fixing frame 36 to be spaced upward
apart from the mover 31. The resonant spring 37 is centrally
coupled to an upper end of the piston 22, and an outer
circumferential edge of the resonant spring 37 is coupled to a
spring supporting member 38 extending upward from the fixing frame
36. The resonant spring 37 configured as described above produces
an exciting force by making use of elasticity thereof, so as to
improve the movability of the piston 22.
[0035] To the resonant spring 37 are mounted a sensor core 41 and a
coil-type displacement detecting sensor 42. The sensor core 41
extends upward from an upper surface of the mover 31 and is
reciprocatable following reciprocating movements of the mover 31
and the piston 22. The displacement detecting sensor 42 detects a
distance of movement of the sensor core 41.
[0036] In the reciprocating compressor configured as described
above, the outer stator 33 produces a magnetic field when an
alternating current is applied to the exciting coil 34 thereof. The
polarity of the produced magnetic field alternates, causing
vertical reciprocating movement of the mover 31 having the magnet
35. As the mover 31 reciprocates, the piston 22 correspondingly
reciprocates to achieve a compression operation, thereby enabling
introduction and discharge of a refrigerant.
[0037] During the compression operation, if an operational
frequency of the piston 22 coincides with a resonant frequency,
i.e. the natural frequency of the compressor, resonance of the
compressor is achieved. This increases the movability of the piston
22 and the mover 31 and improves efficiency of the compressor. As
compared to conventional reciprocating compressors wherein the
resonant frequency is controlled to coincide with typical power
frequency, the reciprocating compressor of the embodiment of the
present invention is controlled so that the resonant frequency of
the compressor is set at a value less than the typical power
frequency. Also, a frequency of input power to be supplied to the
reciprocating compressor corresponds to the resonant frequency,
which is less than the typical power frequency.
[0038] For example, if the typical frequency of the power is 60 Hz,
the resonant frequency of the compressor is set at a value of
approximately 50 Hz, and thus the frequency of the input power is
approximately 50 Hz. In this case, if the resonant frequency and
the frequency of the input power are excessively low, it may result
in a deterioration in the efficiency of the compressor. Thus, when
the typical frequency of the power is 60 Hz, the resonant frequency
and the frequency of the input power are in a range of 35 to 55 Hz,
corresponding to 60% to 90% of the power frequency.
[0039] Such a configuration of the reciprocating compressor as
described above is employed in order to expand the available range
of compression capabilities of the compressor as compared to the
prior art, so that the compressor resonates even in a relatively
low frequency range. This can increase the available range of
compression capabilities depending on a load variation of a cooling
system using the compressor, as well as the efficiency of the
compressor. The fact that the compressor can resonate at the
relatively low frequency range, which is less than the typical
power frequency, means that the compressor can more effectively
operate under a general, low-load, low-speed running condition
(hereinafter, referred to as a normal load condition). The
compressor operates with the operational frequency, which is less
than the frequency of the normal power in the normal load condition
to reduce any possible motor core loss or mechanical friction loss,
which results in the conventionally apparatus.
[0040] FIG. 2 is a control block diagram of the driving unit
provided in the reciprocating compressor of FIG. 1. As shown in
FIG. 2, the driving unit includes an inverter 51 to adjust a
voltage and frequency of input power to be supplied from an
alternating current source 50 to the reciprocating compressor, and
a current detector 53 to detect the frequency of the input power
based on information transmitted from a current sensor 52. The
driving unit further includes: a displacement detector 54 to detect
operational frequencies of the piston 22 and the mover 31 based on
information transmitted from the displacement detecting sensor 42
mounted in the compressor, a load detector 55 to detect a
temperature and discharge and introducing pressures of the
compressor or a load applied to a cooling system containing the
compressor, so as to detect a load applied to the compressor, and a
controller 56 to control the inverter 51 based on information
detected via the current detector 53, the displacement detector 54
and the load detector 55 in order to control the frequency of the
input power being applied to the reciprocating compressor.
[0041] Now, the compression operation of the reciprocating
compressor according to the embodiment of the present invention and
a method for effectively controlling the compression operation will
be explained.
[0042] When power, having a frequency of 60 Hz, is supplied from
the alternating current source 50 to start the compressor, the
normal power is converted into input power having a frequency
corresponding to a resonant frequency of the compressor by the
inverter 51. That is, the frequency of the input power, being
applied from the inverter 51 to the compressor, is approximately 50
Hz, corresponding to the resonant frequency. Thereby, when the
compressor is in a low load state, i.e. normal load state, the
piston 22 reciprocates with an operation frequency of approximately
50 Hz, performing a compression operation. That is, the compressor
resonates in a low frequency range less than the frequency of the
normal power, showing improved operational efficiency in the normal
load state, which occupies a high running percentage of the
compressor.
[0043] In the course of achieving the compression operation as
described above, the controller 56 decides whether the load applied
to the compressor is a normal load or a high load based on
information transmitted from the load detector 55. In the case of
the normal load, the controller 56 controls the inverter 51 so that
the frequency of the input power corresponds to the resonant
frequency of the compressor.
[0044] When the compressor runs in the normal load state, the
controller 56 also controls the inverter 51 so that the frequency
of the input power always corresponds to the resonant frequency
even if the resonant frequency varies depending on a variation of
load applied to the compressor. This enables the compressor to
continuously resonate, and achieves optimized efficiency of the
compressor. During operation of the compressor, although the mass
of moving elements such as the piston 22 and the mover 31 and the
elasticity of the resonant spring 37 are unchangeable, a gas
pressure acting on the piston 22 varies depending on the load
variation, inevitably resulting in a variation of the resonant
frequency. Therefore, in order to continuously maintain the
optimized efficiency of the compressor, the frequency of the input
power varies according to the variation of the resonant frequency
through a control operation of the controller 56.
[0045] Such a control operation achieved by the controller 56 will
now be explained with reference to FIG. 3. That is, in order to
allow the frequency of the input power to follow the resonant
frequency, the displacement detector 54 detects the displacement of
the piston 22 to determine an operational frequency of the
compressor (operation 61), and the current detector 53 determines
the frequency of the input power (operation 62). On the basis of
information determined by the detectors 53 and 54, the controller
56 determines a phase difference between the operational frequency
and the frequency of the input power (operation 63), and decides
whether the determined phase difference is zero, or is greater than
or less than zero. This is done in order to decide the presence and
magnitude of the phase difference (operations 64 and 65). If the
frequency of the input power is equal to the operational frequency,
it can be said that the compressor is in a resonance state.
Therefore, if the phase difference is zero, the controller 56
controls the inverter 51 to continuously maintain the frequency of
the input power frequency (operation 66). If the phase difference
is greater than zero, the controller 56 controls the inverter 51 to
increase the frequency of the input power by calculating a
correction value corresponding to the phase difference (operation
67). If the phase difference is less than zero, the controller 56
controls the inverter 51 to decrease the frequency of the input
power by calculating a correction value corresponding to the phase
difference (operation 68). In this way, on the basis of the
determined phase difference between the frequency of the input
power and the operational frequency, the controller 56 calculates
the correction values to increase or decrease the frequency of the
input power. Thus, the frequency of the input power (or the
operational frequency) is controlled to follow the resonant
frequency even if the resonant frequency varies depending on the
load variation, resulting in optimized efficiency of the
compressor.
[0046] Meanwhile, if the load detector 55 decides that the load
applied to the compressor is higher than the normal load and thus
the compressor is in the high load state, the controller 56
controls the inverter 51 to increase the frequency of the input
power beyond the resonant frequency so that the high frequency of
the input power is applied to the compressor in order to improve
capability of the compressor. That is, as compared to the case of
the normal load, wherein the frequency of the input power is
controlled to coincide with the resonant frequency to maximize the
efficiency of the compressor, in the case of the high load, the
compressor is controlled to operate at the maximum compression rate
possible without causing deterioration of the efficiency of the
compressor. Since the compressor mainly runs in the normal load
state rather than the high load state, the efficiency of the
compressor can be maximized by optimizing the efficiency of the
normal load state, which occupies a high running percentage of the
compressor.
[0047] As is apparent from the above description, the embodiment of
the present invention provides a reciprocating compressor in which
a resonant frequency of the compressor is set at a value less than
a typical power frequency, and a frequency of input power to be
applied to the compressor is controlled to coincide with the
resonant frequency. This expands the available range of compression
capabilities of the compressor to allow the compressor to resonate
even in a relatively low frequency range, which is less than the
typical power frequency, resulting in an improvement in efficiency
of the compressor. This improves the efficiency of the compressor
under a normal load state, which occupies a high running percentage
of the compressor, achieving optimized efficiency of the
compressor.
[0048] Further, according to the embodiment of the present
invention, even if the resonant frequency varies depending on a
variation of a load applied to the compressor during operation of
the compressor, an operational frequency of the compressor is
controlled to follow the varied resonant frequency, so as to allow
the continuous resonance of the compressor, resulting in maximized
efficiency of the compressor.
[0049] Although an embodiment of the present invention has been
shown and described, it would be appreciated by those skilled in
the art that changes may be made in this embodiment without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
* * * * *