US20080008604A1

US20080008604A1 - High-frequency control of devices internal to a hermetic compressor

Info

Publication number: US20080008604A1
Application number: US11/428,942
Authority: US
Inventors: John W. Tolbert
Original assignee: Bristol Compressors Inc
Current assignee: Kulthorn Kirby Public Co Ltd
Priority date: 2006-07-06
Filing date: 2006-07-06
Publication date: 2008-01-10

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.

Description

FIELD OF THE INVENTION

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

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.
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

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.
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.
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.
An advantage of the present invention is that a dual capacity compressor may be controlled without the use of external starting devices.
Another advantage of the present invention is that a modulated capacity compressor may be modulated without additional hermetic terminals.
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

FIG. 1 is a schematic diagram of a control circuit of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a reciprocating hermetic compressor.

FIG. 3 is an illustration of a solenoid-operated bleed valve for a pressure equalization system of a compressor.

FIG. 4 is a diagram of a refrigeration system.

DETAILED DESCRIPTION OF THE INVENTION

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.
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.
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 18 a, 18 b & 18 c for connecting the input AC power line 16. Each AC line 18 a & 18 b may also be used with the start lead (18 c) 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.
In an alternate configuration, lines 18 a to 18 c or 18 b to 18 c 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

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.