U.S. patent application number 11/428942 was filed with the patent office on 2008-01-10 for high-frequency control of devices internal to a hermetic compressor.
This patent application is currently assigned to BRISTOL COMPRESSORS, INC.. Invention is credited to John W. Tolbert.
Application Number | 20080008604 11/428942 |
Document ID | / |
Family ID | 38919302 |
Filed Date | 2008-01-10 |
United States Patent
Application |
20080008604 |
Kind Code |
A1 |
Tolbert; John W. |
January 10, 2008 |
HIGH-FREQUENCY CONTROL OF DEVICES INTERNAL TO A HERMETIC
COMPRESSOR
Abstract
A system for transmitting control signals to internal devices of
a compressor is provided. The compressor includes a housing, a
hermetic power terminal and a motor for powering the compressor.
The system includes a frequency converter that is disposed
externally of the compressor housing. The frequency converter
converts a control signal to a high-frequency signal. A frequency
decoder is disposed inside the compressor housing. The frequency
decoder decodes and converts the high-frequency signal to a driver
signal. An AC input power source provides electrical power to the
motor, and power transmission lines connect the AC input power
source to the hermetic power terminal. The frequency converter is
electrically coupled to the frequency decoder by two power
transmission lines. The frequency decoder generates a driver signal
in response to the high frequency signal for operating at least one
of the internal devices of the compressor.
Inventors: |
Tolbert; John W.; (Bristol,
TN) |
Correspondence
Address: |
MCNEES WALLACE & NURICK LLC
100 PINE STREET, P.O. BOX 1166
HARRISBURG
PA
17108-1166
US
|
Assignee: |
BRISTOL COMPRESSORS, INC.
Bristol
VA
|
Family ID: |
38919302 |
Appl. No.: |
11/428942 |
Filed: |
July 6, 2006 |
Current U.S.
Class: |
417/364 |
Current CPC
Class: |
F04B 39/08 20130101;
F04B 49/035 20130101 |
Class at
Publication: |
417/364 |
International
Class: |
F04B 35/00 20060101
F04B035/00 |
Claims
1. A system for transmitting control signals to internal devices of
a compressor, wherein the compressor includes a housing, a sealed
power terminal, and a motor for powering the compressor, the system
comprising: a first signal converter disposed externally of the
compressor housing, the first signal converter being configured to
receive a control signal and convert the control signal to a
modulated signal; a second signal converter disposed internally of
the compressor housing, the second signal converter being
configured to decode the modulated signal; a plurality of power
transmission lines connected to an AC input power source, the
plurality of power transmission lines also connected to the sealed
power terminal; wherein the first signal converter is electrically
coupled to at least one power transmission line of the plurality of
transmission lines to transmit the modulated signal to the second
signal converter, and the second signal converter is coupled to the
at least one power transmission line and configured to receive the
modulated signal and to generate a driver signal in response to the
modulated signal for operating at least one of the internal devices
of the compressor.
2. The system of claim 1, wherein the first signal converter is a
frequency converter and the second signal converter is a frequency
decoder; the frequency converter configured to convert the
modulated signal to a high-frequency signal.
3. The system of claim 1, wherein the first signal converter
modulates the signal using a modulating technique selected from one
of frequency modulation (FM), amplitude modulation (AM), burst
encoding or digital encoding.
4. The system of claim 1, wherein the second converter is
configured to convert a second signal received from at least one
device disposed within the compressor, and convert the second
signal to a modulated second signal, and the first converter is
configured to receive the modulated second signal and convert the
modulated second signal to a data signal or an external control
signal.
5. The system of claim 1, wherein the at least one internal device
of the compressor is an internal solenoid valve configured to
modulate the capacity of the compressor in response to the
generated driver signal.
6. The system of claim 1, wherein the at least one internal device
of the compressor is an internal solenoid valve, the internal
solenoid valve being disposed between a high-pressure side of the
compressor and a low-pressure side of the compressor, the internal
solenoid valve configured to equalize the high-pressure side and
the low-pressure side in response to the generated driver
signal.
7. The system of claim 6, wherein the internal solenoid valve is a
normally open valve that is actuated to the closed position in
response to the generated driver signal when the compressor is
operating.
8. The system of claim 6, wherein the internal solenoid valve is a
normally closed valve that is actuated to the closed position in
response to the generated driver signal when the compressor is
operating.
9. The system of claim 6, wherein the pressure of the high-pressure
side and the low-pressure side provides reduced torque on the motor
for a delay period.
10. The system of claim 9, wherein the delay period is equal to the
time for the motor to reach a predetermined operating speed.
11. The system of claim 1, wherein the first converter and the
second converter are each connected between a conductor of the AC
input power source and the compressor housing
12. The system of claim 1, wherein the AC input power source is a
multi-phase power source and the first converter and the second
converter are each connected across two corresponding phases of a
multi-phase AC power input.
13. The system of claim 1, wherein the AC input power source is a
single phase power source and the first converter and the second
converter are each connected between a neutral conductor and a
power conductor of the single phase power source.
14. A refrigeration system comprising: a compressor, a condenser,
and an evaporator connected in a closed refrigerant loop the
compressor having a motor to power the compressor and wherein the
compressor includes a housing and a hermetic power terminal; a
frequency converter disposed externally of the compressor housing,
the frequency converter configured to receive a control signal and
convert the control signal to a high-frequency signal; a frequency
decoder disposed internally of the compressor housing, the
frequency decoder configured to decode the high-frequency signal
and convert the high-frequency signal to a driver signal; and a
plurality of power transmission lines connected to the hermetic
power terminal; wherein the frequency converter is electrically
coupled to at least one power transmission line of the plurality of
transmission lines to transmit the high-frequency signal to the
frequency decoder, and the frequency decoder is coupled to the at
least one power transmission line and configured to receive the
high-frequency signal and to generate a driver signal in response
to the high-frequency signal for operating at least one of the
internal devices of the compressor.
15. The system of claim 14, wherein the frequency decoder is
configured to convert a second signal received from at least one
device disposed within the compressor, and convert the second
signal to a second high-frequency signal, and the first converter
is configured to receive the second high-frequency signal and
convert the second high-frequency signal to a data signal or an
external control signal.
16. The system of claim 14, wherein the at least one internal
device of the compressor is an internal solenoid valve configured
to modulate the capacity of the compressor in response to the
generated driver signal.
17. The system of claim 14, wherein the at least one internal
device of the compressor is an internal solenoid valve, the
internal solenoid valve being disposed between a high-pressure side
of the compressor and a low-pressure side of the compressor, the
internal solenoid valve configured to equalize the high-pressure
side and the low-pressure side in response to the generated driver
signal.
18. The system of claim 17, wherein the internal solenoid valve is
a normally open valve that is actuated to the closed position in
response to the generated driver signal when the compressor is
operating.
19. The system of claim 17, wherein the internal solenoid valve is
a normally closed valve that is actuated to the open position in
response to the generated driver signal when the compressor is
operating.
20. The system of claim 17, wherein the pressure of the
high-pressure side and the low-pressure side provides reduced
torque on the motor for a delay period.
21. A method for controlling internal devices of a hermetic
compressor wherein the compressor includes a housing, a hermetic
power terminal and a motor for powering the compressor, the method
comprising: receiving a control signal; converting the control
signal to a high-frequency signal; transmitting the high-frequency
signal on an AC input power line of the compressor; decoding the
high-frequency signal; generating a driver signal in response to
the decoded high-frequency signal; and controlling an internal
device of the hermetic compressor using the generated driver
signal.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to control of hermetic
compressors, and more specifically to the high-frequency control of
devices internal to a hermetic compressor.
BACKGROUND OF THE INVENTION
[0002] Hermetic compressors typically operate through the use of
control devices, e.g., solenoids, that are located inside of the
hermetic compressor housing. In order to provide main supply
voltage and control signals to the devices in the housing, it is
necessary to provide hermetically sealed terminals that penetrate
the hermetic housing for both the main AC voltage power and the
control signal wires. The controller that operates and controls the
internal control devices is generally positioned outside the
hermetic housing of the compressor. Internal devices of the
compressor are typically interconnected to the controller by small
gauge wiring. By way of example, without limitation, capacity
modulation is controlled by a solenoid-actuated slide valve in some
compressors. Also, an internal bleed valve may be used for pressure
equalization on start-up, wherein the bleed valve is controlled by
an electromagnetic solenoid actuator. At least two control wires
are required to conduct the actuation control signals from the
control panel to the solenoid actuator. Additional hermetic
terminals are required to maintain the hermetic integrity of the
housing. Such additional hermetic terminals add to the
manufacturing cost of the compressor, and increase the chances that
the hermetic seal may be compromised.
[0003] What is needed is a convenient, inexpensive means to control
the internal devices in a compressor by using the main AC power
conductors.
SUMMARY OF THE INVENTION
[0004] The present invention is directed to a system for
transmitting control signals to internal devices of a compressor.
The compressor includes a housing, a sealed power terminal, and a
motor for powering the compressor. The system includes a first
signal converter disposed externally of the compressor housing. The
first signal converter is configured to receive a control signal
and convert the control signal to a modulated signal. A second
signal converter is disposed internally of the compressor housing.
The second signal converter is configured to decode the modulated
signal. A plurality of power transmission lines is connected to an
AC input power source. The plurality of power transmission lines is
connected to the sealed power terminal. The first signal converter
is electrically coupled to at least one of the power transmission
lines to transmit the modulated signal to the second signal
converter. The second signal converter is coupled to at least one
power transmission line. The second signal converter is configured
to receive the modulated signal and generate a driver signal in
response to the modulated signal for operating at least one of the
internal devices of the compressor.
[0005] In another embodiment, the invention is directed to a
refrigeration system. The refrigeration system includes a
compressor, a condenser, and an evaporator connected in a closed
refrigerant loop. The compressor has a motor to power the
compressor. The compressor includes a housing and a hermetic power
terminal. A frequency converter is disposed externally of the
compressor housing. The frequency converter is configured to
receive a control signal and convert the control signal to a
high-frequency signal. A frequency decoder is disposed internally
of the compressor housing. The frequency decoder is configured to
decode the high-frequency signal and convert the high-frequency
signal to a driver signal. A plurality of power transmission lines
is connected to the hermetic power terminal. The frequency
converter is electrically coupled to at least one power
transmission line of the plurality of transmission lines to
transmit the high-frequency signal to the frequency decoder. The
frequency decoder is coupled to at least one power transmission
line and configured to receive the high-frequency signal and
generate a driver signal in response to the high-frequency signal
for operating at least one of the internal devices of the
compressor.
[0006] In another embodiment, the invention is directed to a method
for controlling internal devices of a hermetic compressor wherein
the compressor includes a housing, a hermetic power terminal and a
motor for powering the compressor. The method includes generating a
control signal; converting the control signal to a high-frequency
signal; transmitting the high-frequency signal on an AC input power
line of the compressor; decoding the high-frequency signal;
generating a driver signal in response to the decoded
high-frequency signal; and controlling an internal device with the
generated driver signal.
[0007] An advantage of the present invention is that a dual
capacity compressor may be controlled without the use of external
starting devices.
[0008] Another advantage of the present invention is that a
modulated capacity compressor may be modulated without additional
hermetic terminals.
[0009] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram of a control circuit of one
embodiment of the present invention.
[0011] FIG. 2 is a cross-sectional view of a reciprocating hermetic
compressor.
[0012] FIG. 3 is an illustration of a solenoid-operated bleed valve
for a pressure equalization system of a compressor.
[0013] FIG. 4 is a diagram of a refrigeration system.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The description of the high-frequency compressor control
system will be given by reference to the accompanying illustrations
and drawings provided as FIGS. 1 & 2. It is contemplated that
the high-frequency compressor control system may be a component of
a climate control system, including a refrigeration, freezer or
HVAC system, however its use is not limited to such systems as the
high-frequency control system may be used in any system utilizing a
compressor.
[0015] An exemplary embodiment of the high-frequency compressor
control system is generally designated as reference number 10. A
capacity or solenoid start signal S is input to a frequency
converter 12. The signal S is a predetermined control voltage,
preferably in the range of 24 VAC to 230 VAC. The signal S may be
generated by an automatic or manually-operated controller. The
input AC power line 16 is preferably single-phase AC power, but the
invention may also be employed on three-phase and other multi-phase
AC- and DC-input power lines. The output 14 of the frequency
converter 12 may be connected to a single-phase input AC power line
across a power conductor and a neutral conductor, or across two
power conductors. Alternately the output 14 of the frequency
converter 12 may be connected between two phases of a three-phase
input AC power line 16. Finally, the frequency converter 12 may be
connected to any one of the power terminal inputs and a conductor
connected to the compressor housing. In addition, if required,
additional lugs for grounding and neutral connections may also be
provided. The various arrangements described here for connecting
the frequency converter to the input conductors are examples and
the invention is not limited thereto. Those skilled in the art will
appreciate that other coupling arrangement for connecting the
frequency converter 12 may be employed within the spirit and scope
of the present invention.
[0016] The input AC power line 16 is connected to a hermetic power
terminal 18 mounted on the compressor hermetic housing 20. The
hermetic power terminal 18 provides a sealed connection through the
hermetic compressor housing 20. The hermetic power terminal 18
includes connecting lugs 18a, 18b & 18c for connecting the
input AC power line 16. Each AC line 18a & 18b may also be used
with the start lead (18c) connected as a common conductor to
connect the frequency converter 12. Other sealed connections for
penetrating the hermetic housing 20 may also be employed, such as
by way of example and not limitation, airtight packing glands or
conduit connectors capable of maintaining an airtight seal when
exposed to the internal pressures generated by the compressor.
[0017] In an alternate configuration, lines 18a to 18c or 18b to
18c may be used as a single input connection for the frequency
converter 12. This configuration would apply the same for a
three-phase input AC power line. The input AC power line 16 is
connected to a compressor motor 22 through the hermetic power
terminal 18. The motor 22 has motor leads 24 connected to the
hermetic power terminal 18 from the interior of the housing 20.
[0018] In an alternate embodiment, the motor 22 may be powered by
the output of a variable speed drive (VSD) 114 disposed between the
input AC power line. (See, e.g., FIG. 4). In some cases, the
frequency of the input AC power line 16 may be varied by the VSD,
e.g., below 30 Hz, or greater than 90 Hz. If no VSD is used, the
control panel 108 is powered directly by the input AC power line
16, in series with the motor 22.
[0019] The compressor 34 has an internal solenoid valve 26 for
modulating the capacity of the compressor. A frequency
decoder/driver 28 is connected to an electromagnetic coil 30 in the
solenoid valve 26. When the electromagnetic coil 30 of the normally
closed solenoid valve 26 is energized, the valve 26 is opened to
modulate the capacity of the compressor.
[0020] A frequency decoder/driver 28 is connected to the same
phases of the AC input power lines 16 as the frequency converter 12
is connected. Signal S is input to the frequency converter 12 from
a control panel (not shown), to modulate the compressor 34
capacity. Signal S is coupled to the main input AC lines 16 via
frequency converter 12 through control lines 14. The frequency
converter 12 converts signal S from a low frequency signal--e.g.,
50 Hz or 60 Hz--to a high frequency signal--e.g. 10 KHz-100 MHz.
The higher the frequency of the signal, the smaller the coupling
capacitors that are required. Signal S is a low power level signal
relative to the power level of the motor 22. The signal S is
transmitted on main input AC lines 16 through the hermetic power
terminal 18, and into the housing 20 on motor leads 24. Signal S is
coupled to the frequency decoder/driver 28 via control lines 32
connected to motor leads 24. The frequency decoder/driver 28
outputs a driver signal D to the solenoid valve 26 in response to
signal S being detected by frequency decoder/driver 28. The driver
signal D continues to energize the solenoid valve 26 until signal S
is removed by the capacity controller algorithm in the control
panel. When signal S is removed, the solenoid valve 26 closes.
Those skilled in the art will appreciate that there are many known
methods of modulating the high frequency signal, for example,
frequency modulation (FM), amplitude modulation (AM), burst or
digital encoding, and other methods of modulation may be employed
in practicing the present invention.
[0021] In an alternate embodiment, a solid-state or sealed contact
switch (not shown) may be used to energize the solenoid valve 26 by
connecting the solenoid valve 26 across two phases of the motor AC
input mains 24, and actuating the switch via an
externally-connected frequency converter 12.
[0022] In addition to the solenoid valve 26, the high frequency
control system 10 may be used to operate other internal control
devices, such as a bleed valve for pressure equalization. FIG. 3
shows a bleed valve 26 in a pressure equalization system 32 of a
compressor 34 for use in a refrigeration system. The normally open
bleed valve 26 is in the closed state when the compressor 34 is
operating, and open when the compressor 34 is not operating. The
bleed valve 26 permits the equalization of pressure within the
compressor 34 to facilitate startup and to eliminate the need for
motor starting capacitors and start relays.
[0023] As shown in FIG. 4, the refrigeration, HVAC or liquid
chiller system 100 includes a compressor 34, a condenser 104, an
evaporator 106, and a control panel 108. The control panel 108 can
include a variety of different components such as an analog to
digital (A/D) converter, a microprocessor, a non-volatile memory,
and an interface board, to control operation of the refrigeration
system 100. The control panel 108 can also be used to control the
operation of a VSD 114, the motor 22 and the compressor 34.
[0024] Compressor 34 compresses a refrigerant vapor and delivers
the vapor to the condenser 104 through a discharge line. The
compressor 34 is preferably a reciprocating compressor, but can be
any suitable type of compressor, e.g., scroll compressor, rotary
compressor, etc. The refrigerant vapor delivered by the compressor
34 to the condenser 104 enters into a heat exchange relationship
with a fluid, e.g., air or water, but preferably air, and undergoes
a phase change to a refrigerant liquid as a result of the heat
exchange relationship with the fluid. The condensed liquid
refrigerant from condenser 104 flows through an expansion device
(not shown) to an evaporator 106.
[0025] The condensed liquid refrigerant delivered to the evaporator
106 enters into a heat exchange relationship with a fluid, e.g.,
air or water, but preferably air, and undergoes a phase change to a
refrigerant vapor as a result of the heat exchange relationship
with the fluid. The vapor refrigerant in the evaporator 106 exits
the evaporator 106 and returns to the compressor 34 by a suction
line to complete the cycle. It is to be understood that any
suitable configuration of condenser 104 and evaporator 106 can be
used in the system 100, provided that the appropriate phase change
of the refrigerant in the condenser 104 and evaporator 106 is
obtained.
[0026] The HVAC or refrigeration system 100 can include many other
features that are not shown in FIG. 4. These features have been
purposely omitted to simplify the drawing for ease of illustration.
Furthermore, while FIG. 4 illustrates the HVAC refrigeration system
100 as having one compressor connected in a single refrigerant
circuit, it is to be understood that the system 100 can have
multiple compressors, powered by a single VSD or multiple VSDs,
connected into each of one or more refrigerant circuits.
[0027] The following describes the pressure equalization system in
the compressor 34 as it is configured for a refrigeration system
100. The pressure equalization system is connected to the
compressor 34 and has a valve or a series of valves and a bleed
port. The valve or valves maintain high pressure on the high
pressure portion of the refrigeration system, i.e. the valve(s)
maintains a high pressure downstream from the valve to other
components of the refrigeration system, e.g., a condenser and an
expansion valve, when the refrigeration system stops operating. The
bleed port permits the pressure in the compressor 34 to reach a
state of equilibrium between the high pressure side and the low
pressure side of the compressor 34 when the refrigeration system is
turned off. The bleed port can be configured to permit little to no
fluid to pass through when the system is operating but permit fluid
to leak through when the system is turned off. The pressure
equalization system maintains fluid at a high pressure vapor state
on the high pressure portion of the refrigeration system while
permitting fluid in the compressor 34 to reach a state of
equilibrium when the compressor 34 and refrigeration system are
turned off. Upon restarting the compressor 34 and refrigeration
system, it is therefore easier and more efficient to achieve the
high pressure state in the high pressure portion of the system
because most of the high pressure portion of the system has
maintained a high pressure state and has not equalized with the low
pressure portion of the system.
[0028] An exemplary embodiment of a compressor with a pressure
equalization system disposed within the hermetic housing 20 of the
compressor 34 is illustrated in FIG. 2. The pressure equalization
system is disposed within discharge muffler housing 44. The
compressor 34 shown in FIG. 2 is a reciprocating compressor,
although the pressure equalization system 40 may be used with any
compressor, including, for example, a rotary, screw, or scroll
compressor.
[0029] A solenoid valve 26 is shown schematically at aperture 40.
Aperture 40 provides a pressure bleed port between the compressor
housing 20 high-pressure side and the inlet 42 of the compressor
low pressure side. Various solenoid valve arrangements for use with
the present invention are described in commonly owned U.S. Pat. No.
6,584,791 and U.S. Pat. No. 6,823,686, both of which patents are
hereby incorporated by reference.
[0030] Referring to FIG. 3, compressor 34 includes a motor 22
having electrical leads 24 that are connected to the AC input
electrical power source 16 for providing electrical power to the
motor 22. A solenoid valve 26 is connected to the frequency
decoder/driver 28. The valve 26 is connected to the high pressure
side 52 of the compressor 34. The term high pressure side 52 can
refer to any portion of the compressor associated with high
pressure fluid, such as the discharge side of the compression
chamber, including the piston cylinder head, muffler, or shock
loop. Preferably, when opened, the valve 26 permits high pressure
fluid to flow to the low pressure side 54, such as the suction side
of the compressor 34. The valve 26 can be of any construction known
in the art that is compatible for use with the present
invention.
[0031] In a preferred embodiment, the valve 26 may be a
normally-open type of valve. In this configuration the valve is
normally open to permit the flow of high pressure fluid from the
compressor high side elements to the compressor suction or low
pressure side when the compressor 34 is not operating.
[0032] In an alternate embodiment, the valve 26 can be configured
in the normally closed or "off" position. In this configuration the
valve 26 is normally closed to provide a substantially fluid tight
seal to prevent the flow of high pressure fluid from the high
pressure side 52 to the low pressure side 54. In the normally
closed configuration the valve is pulsed open by a signal from the
frequency decoder/driver 28 for a short interval when the
compressor is started.
[0033] Once the valve 26 opens, high-pressure fluid from the
high-pressure side 52 of the compressor flows to the low-pressure
side 54, the valve 26 being sufficiently sized to permit a rapid
change in pressure toward equalization. After this change in
pressure occurs, the motor 22 can then accelerate to its operating
speed requiring substantially reduced starting torque. Preferably,
the valve 26 is sized so that when the compressor is not operating,
i.e., between operating cycles, the pressures in the compressor low
side and high side are completely equalized.
[0034] By providing both equalized pressure and/or an open path
from high side to low side via the open valve at start-up of the
motor 22, the motor requires substantially reduced starting torque.
After a time delay in which the motor may reach its operating
speed, the valve 26 closes in response to a driver signal D from
the frequency decoder/driver 28. The housing 20 must be
sufficiently sized, along with other considerations, such as valve
actuation delay, to ensure the housing 20 does not become overly
pressurized before the motor has reached its operating speed.
[0035] Other control devices that may be controlled through the
frequency converter signals include, by way of example and not
limitation, an internal variable speed drive or other motor control
devices, and mechanical devices for controlling capacity
modulation. The system could also be configured in reverse to
transmit data or control signals from inside the housing to
elements outside the housing, e.g., motor protective devices.
[0036] By using the motor leads 24 and input AC power lines 16 to
transmit the control signal, it is not necessary to create
additional hermetic terminals for control signal wiring, thereby
avoiding the expense of the additional hermetic terminals that
would otherwise be required.
[0037] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *