Abstract: A method and system for detecting and correcting unintended reverse or backward operation of an electric motor driven scroll compressor of a refrigeration system is characterized by monitoring the pressure at a suction side of the compressor during operation of the refrigeration and determining whether the pressure, after a first time interval following startup of the compressor, exceeds and remains in excess of a predetermined upper pressure limit for at least a second time interval. If it does, the compressor is turned off for a third time interval and is then restarted. The foregoing is repeated and if the compressor is turned off a selected number of times because of successive occurrences of high suction side pressures during operation of the refrigeration system in a chilling cycle, an error indication is generated and the refrigeration system is shut down.

Abstract: A recovery system for a frozen product dispenser accommodates automatic recovery and continued operation of the dispenser in response to the output torque of a beater bar and scraper assembly drive motor exceeding a selected upper limit due to transient conditions. A controller monitors the output torque of the drive motor and, upon sensing an output torque in excess of the selected upper limit, shuts off the drive motor and operates a refrigeration system to defrost a freeze barrel within which the beater bar and scraper assembly is rotated, for a time sufficient to defrost product in the barrel. The controller then turns on the drive motor, operates the refrigeration system to refreeze product in the barrel and continues to monitor the output torque of the drive motor. The foregoing operation is repeated several times, if and as necessary, before a system error is generated.

Abstract: A method and system for detecting and correcting unintended reverse or backward operation of an electric motor driven scroll compressor of a refrigeration system is characterized by monitoring the pressure at a suction side of the compressor during operation of the refrigeration and determining whether the pressure, after a first time interval following startup of the compressor, exceeds and remains in excess of a predetermined upper pressure limit for at least a second time interval. If it does, the compressor is turned off for a third time interval and is then restarted. The foregoing is repeated and if the compressor is turned off a selected number of times because of successive occurrences of high suction side pressures during operation of the refrigeration system in a chilling cycle, an error indication is generated and the refrigeration system is shut down.

Abstract: A recovery system for a frozen product dispenser accommodates automatic recovery and continued operation of the dispenser in response to the output torque of a beater bar and scraper assembly drive motor exceeding a selected upper limit due to transient conditions. A controller monitors the output torque of the drive motor and, upon sensing an output torque in excess of the selected upper limit, shuts off the drive motor and operates a refrigeration system to defrost a freeze barrel within which the beater bar and scraper assembly is rotated, for a time sufficient to defrost product in the barrel. The controller then turns on the drive motor, operates the refrigeration system to refreeze product in the barrel and continues to monitor the output torque of the drive motor. The foregoing operation is repeated several times, if and as necessary, before a system error is generated.

Abstract: Diagnostic fault test system and circuit sequentially tests a plurality of drivers (12) and their associated solenoid loads (13). Control signals (PM, SM) are provided to the drivers by a computer controller (11) to achieve desired solenoid actuation. The controller temporarily alters the control signals such that all of the drivers are forced into an on or off state for a first time period (t.sub.A or t.sub.B). After a delay (t.sub.Don or t.sub.Doff) a signal (V.sub.M) associated with each driver stage is monitored to determine if the driver and its load are operating properly. Then the controller resumes normal control of the drivers. The duration of the forced on/off state is short enough so as not to cause a change in the actuated/nonactuated state of the solenoid loads. Each monitored signal from the driver is sequentially compared to a high and low threshold (50, 51) to indicate either proper operation or the identification of one of two different types of fault which may occur.