HIGH EFFICIENCY DC COMPRESSOR AND HVAC/R SYSTEM USING THE COMPRESSOR

Abstract

A DC powered compressor and an HVAC/R system having the compressor are disclosed. The compressor comprises an AC powered compressor and a DC/AC inverter configured to receive power from a DC power source and to provide the power to the AC compressor.

Description

BACKGROUND

Heating, ventilation, air conditioning, and refrigeration (HVAC/R) systems generally have components including a compressor, a condenser fan, and a blower, which each operate according to power received from one or more power sources. Each of these components are powered with either an AC power source or with a DC power source. Compressors powered with DC power are generally power inefficient. Accordingly, an HVAC/R system with a DC powered compressor is generally power inefficient.

SUMMARY OF THE INVENTION

Described herein is a DC compressor, configured to be powered with a DC power source. The DC compressor comprises an AC compressor configured to be powered with an AC power source, and a DC/AC inverter configured to receive power from a DC power source and to provide the power to the AC compressor.

In some embodiments, an HVAC/R system comprises a compressor configured to be powered with an AC power source, and a power supply configured to receive power from a DC power source and to provide the power to the compressor. In some embodiments, the compressor comprises a DC/AC inverter configured to receive power from a DC power source and to provide the power to the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating an HVAC/R system according to one embodiment.

FIG. 2 is a schematic block diagram illustrating an AC Compressor powered with a DC source.

FIG. 3 is a schematic block diagram illustrating an AC Compressor powered with a variable frequency drive (VFD).

FIG. 4 is a schematic block diagram illustrating an AC Compressor powered with a variable frequency drive (VFD) receiving a stepped up voltage from step up module.

FIGS. 5A and 5B are each schematic block diagrams illustrating an embodiment of the step up module of FIG. 4.

FIG. 6 is a schematic illustration of a vapor compression section for an HVAC/R system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 is a schematic block diagram illustrating an HVAC/R system 100 according to one embodiment. The HVAC/R system 100 has a power supply 110 and components which include a compressor 120, a condenser fan 130, and a blower 140. In addition, the HVAC/R system 100 has a control module 150. Each of the components can be powered by either a DC power, an AC single-phase power, or an AC three-phase power. In some embodiments, all components are DC powered. In some embodiments, the components are not all be powered by the same type of power (DC, AC 1-phase, or AC 3-phase). For example, in some embodiments, the compressor 120 and the condenser fan 130 are DC powered, and the blower 140 is AC single-phase powered. All other combinations of DC and AC powering of the components are contemplated.

The power supply 110 is configured to provide power to each of the components and the control module 150 according to the needs of the components and the control module 150. In addition, the control module 150 is configured to provide control signals to the components according to the type of signal (AC or DC) needed by the components.

FIG. 2 is a schematic block diagram illustrating an AC Compressor 125 powered with a DC source. In this embodiment, DC power is provided to a DC/AC inverter 160. The DC/AC inverter 160 is configured to provide AC power (1-phase or 3-phase) to the AC Compressor 125 based on the received DC power. The DC power may be provided by any DC source. For example, the DC power may be provided by a solar source, such as a photo-voltaic source, a battery, or line DC. In some embodiments, the DC power may be provided by a rectified AC source.

FIG. 3 is a schematic block diagram illustrating an AC Compressor 125 powered by a DC source with a variable frequency drive (VFD) 160, also known as a variable speed drive (VSD). In this embodiment, DC power is provided to the VFD 160. The VFD 160 is configured to provide AC power (1-phase or 3-phase) to the AC Compressor 125. The DC power may be provided by any DC source. For example, the DC power may be provided by a solar source, such as a photo-voltaic source, a battery, or line DC. In some embodiments, the DC power may be provided by a rectified AC source.

Use of a VFD to power the compressor 125 allows for speed control, removing the limitation on the system to be either fully on or off. For example, an HVAC/R system with a VFD can operate the compressor at a speed corresponding to the cooling requirements of the environment having its temperature controlled. For example, if the controlled environment generates 500 watts of power, the compressor can be operated at a speed that corresponds to the heat generated by the 500 watts. This allows for improved power efficiency in the system because power inefficiencies experienced with repeatedly starting and stopping the compressor is avoided.

Furthermore, in some controlled environments, such as well insulated spaces, the heat generated is relatively constant. Accordingly, the energy to be removed is relatively constant. For such environments, the compressor motor may be designed for operation according to the load corresponding to the relatively constant energy to be removed. Such limited range of load allows for the compressor to be efficiently operated.

Another benefit to speed control is that the range of temperatures in controlled environment is dramatically reduced when compared to conventional HVAC/R systems in which the compressor is either fully on or off. In conventional HVAC/R systems, in order to prevent frequent state changes between off and on, the control system works with a hysteresis characteristic. In such systems, temperature excursions correspond to the hysteresis. For example, in some systems the hysteresis of the system is 3 degrees. If the temperature is set to −5 C, once the temperature of the environment is −5 C, the compressor is turned off. However, because of the 3 degrees of hysteresis, the compressor will not be turned on again until the temperature of the environment is −2 C. In contrast, in an HVAC/R system with a VFD controlling the compressor, the active control system incrementally increases and decreases the speed of the compressor to provide precise control of the temperature in the environment. As a result, there is no hysteresis, and, accordingly, significantly reduced trade-off between consistency of temperature and power consumption.

FIG. 4 is a schematic block diagram illustrating a system 400 with an AC Compressor 125, a VFD 160, and a step up module 170. In the system 400 the AC compressor 125 is powered with a VFD 160 receiving a stepped up voltage from a step up module 170. The step up module 170 may receive DC power from any DC source. Having a stepped up voltage is particularly advantageous where applications prefer to use few storage batteries, but still use a high voltage for the AC compressor 125. For example, in system 400 the DC source may be one 12V DC battery, and the VFD may use a higher voltage. Accordingly, the step up module 170 is used to step up the voltage from about 12V DC to the higher voltage.

FIGS. 5A and 5B are schematic block diagrams each illustrating embodiments of a step up module. In FIG. 5A, step up module 500 includes two 12V DC to 120V AC inverters 84 and 85, rectifiers 86 and 87, and filter 88. Step up module 500 is configured to generate about a 330V DC signal based on an about 24V DC input signal applied across the positive terminal of inverter 84 and the negative terminal of inverter 85.

The about 24V DC signal can be provided by any DC source. In some embodiments, the about 24V DC signal is provided by two about 12V batteries.

The two inverters 84 and 85 are each configured to receive a 12V DC input and output a 120V rms AC signal. In some embodiments, the DC power source 60, the inverters 84 and 85 are serially connected across the 24-volt DC input. Accordingly, the inverters 84 and 85 each receive an about 12V input. In response to the 12V input, the inverters 84 and 85 each produce an AC signal of about 120V rms.

The 120V rms AC signal of inverter 84 is provided to rectifier 87, and the 120V rms AC signal of inverter 85 is provided to rectifier 86. The rectifiers 86 and 87 rectify the respective AC signals producing substantially DC outputs of about 165V each. The rectifiers 86 and 87 are connected in series, and therefore collectively produce a substantially summed DC signal of about 330V. In the embodiment shown in FIG. 5A, the rectifiers 86 and 87 are each shown as a four diode bridge rectifier in parallel with a capacitor. Other rectifier configurations may be used.

The filter 88 is connected across the serially connected rectifiers 86 and 87. The filter is configured to improve the quality of the DC output signal by filtering non-DC components of the signal produced by the rectifiers 86 and 87. As shown in FIG. 5A, the filter 88 is a single capacitor. In other embodiments other filters may be used.

In FIG. 5B, step up module 550 includes two 12V DC to 120V AC inverters 84 and 85, rectifiers 86 and 87, and filter 88. Step up module 550 is configured to generate an about 330V DC signal based on an about 12V DC input signal applied across the positive and negative terminals of each of inverter 84 and inverter 85. In this embodiment, rectifiers 86 and 87 are used to produce two substantially DC signals of about 165V each. As in the embodiment of FIG. 5B, the rectifiers are connected in series to produce a summed substantially DC 330V signal. Because of the arrangement of the inverters 84 and 85 and the rectifiers 86 and 87, the substantially DC voltage produced is independent of the frequency and phase of each of the AC signals of the inverters 84 and 85.

In another embodiment, an HVAC/R system as described above incorporates a pulsed operation control valve to control refrigerant flow to the evaporator from the condenser. The VFD powered HVAC/R system yields varying compressor-speeds resulting in variable refrigerant flows to the condenser and to the evaporator. However, conventional expansion devices such as capillary tubes or expansion valves (AEV or TEV) cannot handle or take advantage of varying refrigerant flows and hunt or flood, thereby reducing evaporator efficiency and system performance. In order to achieve desired advantages of such variable refrigerant flows, according to this embodiment, a pulsing refrigerant control valve is used to produce a full range of evaporator superheat control at all refrigerant flows without starving or flooding the evaporator. Such refrigerant control is especially important at lower refrigerant flow rates resulting from variable compressor speeds. Conventional expansion devices are designed to operate at full flow and are inefficient at lower flows, and fluctuating flows, again, starving and/or flooding the evaporator. The pulsing valve may be a mechanical valve such as described in U.S. Pat. Nos. 5,675,982 and 6,843,064 or an electrically operated valve of the type described in U.S. Pat. No. 5,718,125, the descriptions of which are incorporated herein by reference in their entireties. Such valves operate to control refrigerant-flow to the evaporator throughout the variable refrigerant flow ranges from the compressor and condenser.

FIG. 6 schematically illustrates a vapor compression section of an HVAC/R system such as that of FIG. 1. A pulsed operation control valve 410 is installed in liquid refrigerant line 412 of a refrigerant loop piping that directs refrigerant from condenser 420 to evaporator 430. In this embodiment, a compressor 352 is powered by VFD 322, and condenser 420 is cooled by condenser fan 354.

While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices and processes illustrated may be made by those skilled in the art without departing from the spirit of the invention. For example, inputs, outputs, and signals are given by example only. As will be recognized, the present invention may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others. Moreover, it is to be understood that the HVAC/R systems described herein may be configured as air conditioners, chillers, heat pumps and refrigeration systems.

Claims

1. A DC compressor, configured to be powered with a DC power source, the DC compressor comprising:

a DC/AC inverter configured to receive power from a DC power source and to provide AC power; and

an AC compressor configured to be powered from the AC power from the DC/AC inverter.

2. The DC compressor of claim 1, wherein the AC compressor is configured to be powered with a three-phase AC signal from the inverter.

3. The DC compressor of claim 1, wherein the AC compressor is configured to be powered with a single-phase AC signal from the inverter.

4. The DC compressor of claim 1, wherein the inverter comprises a variable frequency drive (VFD).

5. The DC compressor of claim 4, further comprising a control module configured to vary the speed of the AC compressor with the VFD.

6. The DC compressor of claim 4, further comprising a step up module configured to provide a DC power voltage to the VFD based on a DC input voltage, wherein the DC power voltage is less than the DC input voltage.

7. The DC compressor of claim 6, wherein the DC input voltage is about 24V DC.

8. The DC compressor of claim 6, wherein the DC input voltage is about 12V DC.

9. The DC compressor of claim 6, wherein the DC power voltage is about 330V DC.

10. The DC compressor of claim 6, wherein the step up module comprises a plurality of inverters each connected to a rectifier.

11. The DC compressor of claim 10, wherein the rectifiers are connected in series so as to sum the voltages produced by the rectifiers.

12. The DC compressor of claim 10, wherein each of the inverters comprises a pair of input terminals, and the DC input voltage is applied across the pair of terminals of each of the inverters.

13. The DC compressor of claim 10, wherein each of the inverters comprises a pair of input terminals, and the inverters are connected in a series such that a positive terminal of a first inverter is connected to a negative terminal of a next inverter, and the DC input voltage is applied across a negative terminal of the first inverter and a positive terminal of a last inverter of the series.

14. An HVAC/R system comprising:

a compressor configured to be powered with an AC power source; and

a power supply configured to receive power from a DC power source and to provide the power to the compressor.

15. The HVAC/R system of claim 14, wherein the power supply comprises a DC/AC inverter.

16. The HVAC/R system of claim 14, wherein the compressor is configured to be powered with a three-phase AC signal from the power supply.

17. The HVAC/R system of claim 14, wherein the compressor is configured to be powered with a single-phase AC signal from the power supply.

18. The HVAC/R system of claim 14, wherein the power supply comprises a variable frequency drive (VFD).

19. The HVAC/R system of claim 18, further comprising a control module configured to vary the speed of the compressor with the VFD.

20. The HVAC/R system of claim 19, further comprising a condenser, an evaporator, and a refrigerant loop including piping for directing refrigerant from the compressor to the condenser and from the condenser to the evaporator, and a pulsed operation control valve in said piping for controlling refrigerant flow to said evaporator.

21. The HVAC/R system of claim 18, further comprising a step up module configured to provide a DC power voltage to the VFD based on a DC input voltage, wherein the DC power voltage is less than the DC input voltage.

22. The HVAC/R system of claim 21, wherein the DC input voltage is about 24V DC.

23. The HVAC/R system of claim 21, wherein the DC input voltage is about 12V DC.

24. The HVAC/R system of claim 21, wherein the DC power voltage is about 330V DC.

25. The HVAC/R system of claim 21, wherein the step up module comprises a plurality of inverters each connected to a rectifier.

26. The HVAC/R system of claim 25, wherein the rectifiers are connected in series so as to sum the voltages produced by the rectifiers.

27. The HVAC/R system of claim 25, wherein each of the inverters comprises a pair of input terminals, and the DC input voltage is applied across the pair of terminals of each of the inverters.

28. The HVAC/R system of claim 25, wherein each of the inverters comprises a pair of input terminals, and the inverters are connected in a series such that a positive terminal of a first inverter is connected to a negative terminal of a next inverter, and the DC input voltage is applied across a negative terminal of the first inverter and a positive terminal of a last inverter of the series.

29. The HVAC/R system of claim 14, further comprising a condenser, an evaporator, and a refrigerant loop including piping for directing refrigerant from the compressor to the condenser and from the condenser to the evaporator, and a pulsed operation control valve in said piping for controlling refrigerant flow to said evaporator.