Electronic control system for regulating startup operation of a compressor in a refrigeration system

A method of controlling flow of vaporous refrigerant from an evaporator to a compressor in a hermetically sealed refrigeration system during startup of the system, said method comprising the steps of:

• measuring a refrigerant pressure or temperature corresponding to a gaseous refrigerant pressure at a location between the compressor and in the evaporator at the startup of the refrigeration system and at selected times thereafter;
• generating electrical signals corresponding to the magnitude of each measured pressure;
• electronically processing the electrical signals corresponding to the measured pressures to determine the actual rate of decrease in refrigerant pressure;
• electronically comparing the rate of decrease of refrigerant pressure to a predetermined rate of decrease of pressure;
• generating an electrical control signal when the difference between the predetermined rate and the actual rate is less than a first preselected limit and generating a second electrical control signal when the difference between the predetermined rate and the actual rate is greater than a second preselected limit;
• and
• adjusting the capacity of the compressor in response to the electrical control signals to adjust the actual rate to approximately equal the predetermined rate.

In a refrigeration system having an evaporator, a condenser, a compressor, a hermetically sealed compressor transmission housing containing a lubricating oil reservoir and a lubricating oil pump the combination comprising:

• a suction line connecting the compressor inlet to the evaporator to allow the flow of gaseous refrigerant from the evaporator to the compressor;
• flow control means in the suction line to regulate the flow of gaseous refrigerant from the evaporator to the compressor;
• a pressure equalization line connecting the suction line to the transmission housing to equalize the pressure in the housing with the pressure in the suction line;
• means for determining the pressure in the evaporator and for generating electrical signals indicative of the pressure in the evaporator;
• electronic control means for receiving the electrical signals indicative of the pressure in the evaporator and for comparing the electrical signals to a preprogrammed series of electrical signals which correspond to a predetermined rate of pressure decrease for the evaporator;
• and
• means for positioning the flow control means in response to signals from the electronic control means to regulate the pressure in the suction line and in the transmission housing.