Method and system for cooling a motor during motor startup

Abstract

A HVAC system includes a compressor having a low pressure input and a high pressure output. The compressor is driven by a motor having a liquid coolant flowpath configured to cool and lubricate the motor. The motor has a coolant input and a coolant output. An evaporator is in communication with the compressor, and includes a coolant input and a coolant output. A condenser is in fluid communication with the evaporator and the compressor. A first coolant flowpath, includes a coolant drive system connecting the output of the condenser to a valve switching device. A second coolant flowpath connects the output of the condenser to the input of the evaporator and to a second input of the valve switching device. A third coolant flowpath connects the valve switching device to the inputs of the motor. A fourth coolant flowpath connects outputs of the motor to the input of the evaporator.

1 . A heating ventilation and air conditioning (HVAC) system comprising:
 a compressor comprising a low pressure input and a high pressure output, the compressor driven by a motor, the motor including a liquid coolant flowpath configured to cool and lubricate the motor and having a liquid coolant input and a liquid coolant output;   an evaporator in fluid communication with the compressor, the evaporator including a liquid coolant input, and a vapor coolant output, the vapor coolant output being connected to the low pressure input of the compressor;   a condenser in fluid communication with the evaporator and the compressor, the condenser including a vapor cooling input and a liquid coolant output, the vapor cooling input being connected to a high pressure output of the compressor;   a first liquid coolant flowpath, including a liquid coolant drive system connecting the liquid coolant output of the condenser to the input of a valve switching device;   a second liquid coolant flowpath connecting the liquid coolant output of the condenser to the liquid input of the evaporator and to a second input of the valve switching device;   a third liquid coolant flowpath connecting an output of the valve switching device to the liquid coolant inputs of the motor; and   a fourth liquid coolant flowpath connecting the liquid coolant outputs of the motor to the liquid coolant input of the evaporator.   
     
     
         2 . The HVAC system of  claim 1 , wherein the liquid coolant drive system comprises an electric pump. 
     
     
         3 . The HVAC system of  claim 2 , wherein the electric pump is disposed within a reservoir integrated into the condenser. 
     
     
         4 . The HVAC system of  claim 2 , wherein the electric pump is disposed within a reservoir exterior to the condenser. 
     
     
         5 . The HVAC system of  claim 2  wherein the electric pump is disposed outside of the condenser. 
     
     
         6 . The HVAC system of  claim 2 , further comprising a controller controllably connected to the valve switching device, the electric pump and the motor. 
     
     
         7 . The HVAC system of  claim 6 , wherein the controller is configured to activate the electric pump at least five seconds prior to activating the motor. 
     
     
         8 . The HVAC system of  claim 1 , wherein the liquid coolant drive system comprises a liquid coolant reservoir. 
     
     
         9 . The HVAC system of  claim 8 , wherein the liquid coolant reservoir is disposed above the motor, relative to a force of gravity, such that a liquid coolant is gravity fed from said reservoir to said motor when the valve switching device is in a first state. 
     
     
         10 . The HVAC system of  claim 8 , wherein the liquid coolant reservoir includes an electric heater disposed within the liquid coolant reservoir. 
     
     
         11 . The HVAC system of  claim 10 , wherein the electric heater is controllably coupled to a controller, and the controller is configured to activate the electric heater at least 5 minutes prior to activating the motor. 
     
     
         12 . The HVAC system of  claim 8 , further comprising a one way valve disposed in the first liquid coolant flowpath between the liquid coolant output of the condenser and the input to the reservoir, and oriented such that liquid coolant flows from the condenser to the reservoir and is prevented from flowing from the reservoir to the condenser. 
     
     
         13 . The HVAC system of  claim 1 , wherein the liquid coolant flowpath includes a liquid phase R1233zd(E) (CHCl=CH=CF3) refrigerant. 
     
     
         14 . The HVAC system of  claim 1 , wherein the second liquid coolant flowpath includes an expansion device connecting the liquid coolant output of the condenser to the liquid input of the evaporator. 
     
     
         15 . The HVAC system of  claim 1 , wherein the first liquid coolant flowpath includes a check valve connecting the liquid coolant output of the condenser to the liquid coolant drive system. 
     
     
         16 . A method for operating a heating ventilation and air conditioning (HVAC) system comprising:
 driving a liquid coolant from a condenser to a compressor motor during a startup sequence of the compressor motor using a liquid coolant drive system, thereby cooling and lubricating the compressor motor; and   drawing liquid coolant from the condenser to the compressor motor using a pressure differential between the condenser and an evaporator once the startup sequence has completed.   
     
     
         17 . The method of  claim 16 , wherein driving the liquid coolant comprises providing liquid coolant from the condenser to a reservoir and heating the liquid coolant in the reservoir, thereby increasing a pressure of the liquid coolant. 
     
     
         18 . The method of  claim 16 , wherein driving the liquid coolant comprises operating an electric pump disposed within the condenser. 
     
     
         19 . The method of  claim 16 , wherein driving the liquid coolant comprises operating an electric pump disposed between an outlet of the condenser and a liquid coolant inlet of the compressor motor. 
     
     
         20 . The method of  claim 16 , further comprising transitioning from driving the liquid coolant using the liquid coolant driving system to drawing liquid coolant from the condenser to the compressor motor using a pressure differential between the condenser and the evaporator in response to the compressor motor exceeding a rotational speed.