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

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 asFIGS. 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 number10. A capacity or solenoid start signal S is input to afrequency converter12. 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 inputAC power line16 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. Theoutput14 of thefrequency converter12 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 theoutput14 of thefrequency converter12 may be connected between two phases of a three-phase inputAC power line16. Finally, thefrequency converter12 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 thefrequency converter12 may be employed within the spirit and scope of the present invention.
• The inputAC power line16 is connected to ahermetic power terminal18 mounted on the compressorhermetic housing20. Thehermetic power terminal18 provides a sealed connection through thehermetic compressor housing20. Thehermetic power terminal18 includes connectinglugs18a,18b&18cfor connecting the inputAC power line16. EachAC line18a&18bmay also be used with the start lead (18c) connected as a common conductor to connect thefrequency converter12. Other sealed connections for penetrating thehermetic housing20 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,lines18ato18cor18bto18cmay be used as a single input connection for thefrequency converter12. This configuration would apply the same for a three-phase input AC power line. The inputAC power line16 is connected to acompressor motor22 through thehermetic power terminal18. Themotor22 has motor leads24 connected to thehermetic power terminal18 from the interior of thehousing20.
• In an alternate embodiment, themotor22 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 inputAC power line16 may be varied by the VSD, e.g., below 30 Hz, or greater than 90 Hz. If no VSD is used, thecontrol panel108 is powered directly by the inputAC power line16, in series with themotor22.
• Thecompressor34 has aninternal solenoid valve26 for modulating the capacity of the compressor. A frequency decoder/driver28 is connected to anelectromagnetic coil30 in thesolenoid valve26. When theelectromagnetic coil30 of the normally closedsolenoid valve26 is energized, thevalve26 is opened to modulate the capacity of the compressor.
• A frequency decoder/driver28 is connected to the same phases of the ACinput power lines16 as thefrequency converter12 is connected. Signal S is input to thefrequency converter12 from a control panel (not shown), to modulate thecompressor34 capacity. Signal S is coupled to the maininput AC lines16 viafrequency converter12 throughcontrol lines14. Thefrequency converter12 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 themotor22. The signal S is transmitted on maininput AC lines16 through thehermetic power terminal18, and into thehousing20 on motor leads24. Signal S is coupled to the frequency decoder/driver28 viacontrol lines32 connected to motor leads24. The frequency decoder/driver28 outputs a driver signal D to thesolenoid valve26 in response to signal S being detected by frequency decoder/driver28. The driver signal D continues to energize thesolenoid valve26 until signal S is removed by the capacity controller algorithm in the control panel. When signal S is removed, thesolenoid valve26 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 thesolenoid valve26 by connecting thesolenoid valve26 across two phases of the motorAC input mains24, and actuating the switch via an externally-connectedfrequency converter12.
• In addition to thesolenoid valve26, the high frequency control system10 may be used to operate other internal control devices, such as a bleed valve for pressure equalization.FIG. 3 shows ableed valve26 in apressure equalization system32 of acompressor34 for use in a refrigeration system. The normallyopen bleed valve26 is in the closed state when thecompressor34 is operating, and open when thecompressor34 is not operating. Thebleed valve26 permits the equalization of pressure within thecompressor34 to facilitate startup and to eliminate the need for motor starting capacitors and start relays.
• As shown inFIG. 4, the refrigeration, HVAC orliquid chiller system100 includes acompressor34, acondenser104, anevaporator106, and acontrol panel108. Thecontrol panel108 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 therefrigeration system100. Thecontrol panel108 can also be used to control the operation of aVSD114, themotor22 and thecompressor34.
• Compressor34 compresses a refrigerant vapor and delivers the vapor to thecondenser104 through a discharge line. Thecompressor34 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 thecompressor34 to thecondenser104 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 fromcondenser104 flows through an expansion device (not shown) to anevaporator106.
• The condensed liquid refrigerant delivered to theevaporator106 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 theevaporator106 exits theevaporator106 and returns to thecompressor34 by a suction line to complete the cycle. It is to be understood that any suitable configuration ofcondenser104 andevaporator106 can be used in thesystem100, provided that the appropriate phase change of the refrigerant in thecondenser104 andevaporator106 is obtained.
• The HVAC orrefrigeration system100 can include many other features that are not shown inFIG. 4. These features have been purposely omitted to simplify the drawing for ease of illustration. Furthermore, whileFIG. 4 illustrates theHVAC refrigeration system100 as having one compressor connected in a single refrigerant circuit, it is to be understood that thesystem100 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 thecompressor34 as it is configured for arefrigeration system100. The pressure equalization system is connected to thecompressor34 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 thecompressor34 to reach a state of equilibrium between the high pressure side and the low pressure side of thecompressor34 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 thecompressor34 to reach a state of equilibrium when thecompressor34 and refrigeration system are turned off. Upon restarting thecompressor34 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 thehermetic housing20 of thecompressor34 is illustrated inFIG. 2. The pressure equalization system is disposed withindischarge muffler housing44. Thecompressor34 shown inFIG. 2 is a reciprocating compressor, although thepressure equalization system40 may be used with any compressor, including, for example, a rotary, screw, or scroll compressor.
• Asolenoid valve26 is shown schematically ataperture40.Aperture40 provides a pressure bleed port between thecompressor housing20 high-pressure side and theinlet42 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 toFIG. 3,compressor34 includes amotor22 havingelectrical leads24 that are connected to the AC inputelectrical power source16 for providing electrical power to themotor22. Asolenoid valve26 is connected to the frequency decoder/driver28. Thevalve26 is connected to thehigh pressure side52 of thecompressor34. The termhigh pressure side52 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, thevalve26 permits high pressure fluid to flow to thelow pressure side54, such as the suction side of thecompressor34. Thevalve26 can be of any construction known in the art that is compatible for use with the present invention.
• In a preferred embodiment, thevalve26 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 thecompressor34 is not operating.
• In an alternate embodiment, thevalve26 can be configured in the normally closed or “off” position. In this configuration thevalve26 is normally closed to provide a substantially fluid tight seal to prevent the flow of high pressure fluid from thehigh pressure side52 to thelow pressure side54. In the normally closed configuration the valve is pulsed open by a signal from the frequency decoder/driver28 for a short interval when the compressor is started.
• Once thevalve26 opens, high-pressure fluid from the high-pressure side52 of the compressor flows to the low-pressure side54, thevalve26 being sufficiently sized to permit a rapid change in pressure toward equalization. After this change in pressure occurs, themotor22 can then accelerate to its operating speed requiring substantially reduced starting torque. Preferably, thevalve26 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 themotor22, the motor requires substantially reduced starting torque. After a time delay in which the motor may reach its operating speed, thevalve26 closes in response to a driver signal D from the frequency decoder/driver28. Thehousing20 must be sufficiently sized, along with other considerations, such as valve actuation delay, to ensure thehousing20 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 leads24 and inputAC power lines16 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 (21)

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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 9, wherein the delay period is equal to the time for the motor to reach a predetermined operating speed.

11. The system ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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.

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