Patent Application
20080008604
The description of the high-frequency compressor control system will be given by reference to the accompanying illustrations and drawings provided as
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 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.
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.
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.,
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.
As shown in
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
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
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
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.
