Multi-capacity compressor with variable speed drive and method of use

1 . A system for controlling a capacity of a multi-capacity compressor operable at each of a plurality of capacity levels, the system comprising:

a motor of the multi-capacity compressor;

a drive configured to control a speed of the motor;

a switch network coupled to a line-voltage source, the drive, and the multi-capacity compressor; and

a controller configured to control the drive and the switch network, and configured to:

selectively couple the multi-capacity compressor to either (a) the line-voltage source or (b) the drive; and

selectively control the multi-capacity compressor to operate at each of:

a first capacity to provide a first output power, or

a second capacity to provide a second output power different than the first output power,

wherein the selective coupling and the selective controlling cause the compressor to operate in each of:

a first mode, powered by the drive, and at the first capacity,

a second mode, powered by the line-voltage source, and at the first capacity, or

a third mode, powered by the line-voltage source, and at the second capacity.

2 . An HVAC system comprising the system of claim 1 , the HVAC system further comprising:

a heat exchanger in fluid communication with the compressor;

an expansion valve in fluid communication with the heat exchanger; and

a blower configured to generate an interior airflow via the heat exchanger.

3 . The system of claim 1 , wherein the line-voltage source is configured to provide an alternating current (AC) voltage.

4 . The system of claim 1 , wherein the controller is further configured to:

determine a working load for the compressor; and

select, based on the working load, a capacity setting at which the compressor is to operate, the capacity setting selected from among the first mode, the second mode, and the third mode.

5 . The system of claim 4 , wherein the controller is further configured to:

select the first mode when the working load is below a first threshold;

select the second mode when the working load is above the first threshold and below a second threshold; and

select the third mode when the working load is above the second threshold.

6 . The system of claim 5 , wherein the controller is further configured to:

determine the first threshold and the second threshold based on a temperature set point for an interior space.

7 . The system of claim 5 , wherein the controller is further configured to:

determine the first threshold and the second threshold based on a measured ambient temperature of an exterior space.

8 . The system of claim 1 , comprising a main system relay configured to switch the line-voltage source to the compressor.

9 . The system of claim 1 , wherein the controller is further configured to cause a plurality of switches to selectively couple the compressor based on a first threshold or a second threshold.

10 . The system of claim 9 , wherein the controller is further configured to determine the first threshold and the second threshold in response to a temperature set point for an interior space.

11 . The system of claim 9 , wherein the controller is further configured to determine the first threshold and the second threshold in response to a measured ambient temperature of an exterior space.

12 . The system of claim 1 , wherein the compressor is a two-stage compressor.

13 . A heating ventilation and air conditioning (HVAC) system comprising:

a multi-stage compressor operable at each of a plurality of capacity levels;

a variable-voltage, variable-frequency drive coupled to a line-voltage source and configured to operate the multi-stage compressor at a variable speed, wherein the line voltage source is configured to provide an alternating current (AC) voltage; and

a controller configured to:

selectively couple the line-voltage source or the variable-voltage, variable-frequency drive to the multi-stage compressor to power the multi-stage compressor; and

selectively control the multi-stage compressor to operate at each of:

a first capacity to provide a first output power, or

a second capacity to provide a second output power different than the first output power,

wherein the selective coupling and the selective controlling cause the multi-stage compressor to operate in each of:

a first mode, powered by the variable-voltage, variable-frequency drive, and at the first capacity,

a second mode, powered by the line-voltage source, and at the first capacity, or

a third mode, powered by the line-voltage source, and at the second capacity.

14 . The HVAC system of claim 13 , wherein the controller is configured to:

determine, based on a working load, an operation speed of the variable-voltage, variable-frequency drive; and

transmit a speed-control signal to the variable-voltage, variable-frequency drive to operate at the operation speed.

15 . The HVAC system of claim 13 , wherein the controller is configured to:

determine a working load for the multi-stage compressor; and

select, based on the working load, a capacity setting at which the multi-stage compressor is to operate, the capacity setting selected from among the first mode, the second mode, and the third mode.

16 . The HVAC system of claim 15 , wherein the controller is configured to:

select the first mode when the working load is below a first threshold;

select the second mode when the working load is above the first threshold and below a second threshold; and

select the third mode when the working load is above the second threshold.

17 . The HVAC system of claim 16 , wherein the controller is configured to:

determine the first threshold and the second threshold based on a temperature set point for an interior space.

18 . The HVAC system of claim 16 , wherein the controller is configured to:

determine the first threshold and the second threshold based on a measured ambient temperature of an exterior space.

19 . The HVAC system of claim 13 , wherein the line-voltage source comprises a switch network through which the AC voltage is switched, the AC voltage comprising a 60-Hertz 240-volt signal.