Abstract: A safety device for preventing the automatic restart of a motor upon restoration of power to the motor. This device, in its preferred embodiment, includes a thyristor switch, such as a triac, in one of the power leads to the motor which is triggered by energizaton of the motor. Upon deenergizaton of the motor, the thyristor switch switches to its non-conductive state thereby preventing automatic restarting of the motor upon restoration of the power. A selectively actuable, momentary run switch is provided to momentarily shunt out the thyristor switch so as to selectively permit the restart of the motor.

Abstract: Method and apparatus for monitoring a plurality of thermal parameters and the pressure related work load of a motor-compressor unit utilized in a heat pump system and providing protection for the motor-compressor by turning off the system for time periods dependent upon which parameter caused the system to be turned off.

Abstract: A refrigerating system having a compressor; an inverter connected to the compressor for supplying electric energy to the compressor; and an input voltage control circuit provided on the input side of the inverter, wherein the input voltage control circuit generates output voltage signals which change at a predetermined level, including zero level, within a certain temperature range in response to the ambient temperature of the refrigerating system and in accordance with the temperature condition, the voltage thus produced being fed to the compressor via the inverter. The refrigerating system of this invention is, therefore, protected from failure or damage even when placed in an extreme temperature environment, and resumes automatically the supply of power to the compressor when the ambient temperature of the system is restored to the normal temperature.

Abstract: A control circuit is provided for a contactor which has a pair of contacts and an actuator coil which is energizable under the control of a switch to cause the contacts to close. The control circuit provides a temporary path for energizing the coil and a permanent path through the contacts. The control circuit delays energization of the coil for a preselected time to allow switch contact bounce to cease. The control circuit prevents a reestablishment of the temporary path for preselected time after the contacts close.

Abstract: A low voltage protection circuit for an air conditioner compressor which employs a series of diodes to control the application of an a.c. source potential to the resistive heater element of a conventional thermally responsive switch. The diode circuit maintains the heater element directly across the source potential at all times when the thermally responsive switch is open, but only during alternate half-cycles of the source potential when the thermally responsive switch is closed to thereby protect the compressor against potentially damaging low voltage conditions while reducing the power consumed by the heater element during periods of normal source voltage level.

Abstract: An automatic control apparatus for protecting the compressor motor used with the refrigeration system of an air conditioning unit. The control apparatus has a timer for prohibiting the restart of the compressor motor until the lapse of a predetermined time after temporary stoppage of the compressor motor, and a holding circuit for holding a power source voltage for a predetermined period of time while the operation of the air conditioning unit is stopped. Even if the power supply is turned off, therefore, the source voltage supplied by the holding circuit enables the timer circuit to continue its operation for a predetermined length of time.

Abstract: A minimum off-time protection arrangement is disclosed for compressors, particularly refrigeration type compressors. A current transformer is placed in the circuit which controls the switching of the compressor and that current transformer provides a control signal to a minimum off-time circuit. The minimum off-time circuit prevents the compressor from being restarted for some minimum period of time after once being operated.

Abstract: A solid state starter for a chiller compressor motor mounts directly on the compressor motor and comprises a bank of SCR's which are controllably switched to conduct current to the motor for starting and running. Electronic control modules are provided including a trigger module for triggering the SCR's, a current module (including current overload protection) for controlling the trigger module so that motor current is controllably delivered to the motor, and a voltage safety module for protecting against electrical faults. The SCR's are cooled by liquid refrigerant.

Abstract: A motor is electrically coupled to a power source through a motor starter. The motor is selectively operated by a relay to connect and disconnect the power source to the motor. A counter accumulates a count of motor failures and produces an inhibit signal should the frequency of occurrence of such motor failures exceed a given level. The relay is operated by an inhibit signal to cause the motor starter to disconnect the power source from the motor.

Abstract: A control system for a central air conditioner. The air conditioner includes an outdoor condensing unit including a refrigerant compressor, an indoor evaporator unit, an indoor thermostat responsive to the indoor temperature for controlling the air conditioner, and a control system for protecting the air conditioner and indicating to the user certain malfunctions in the air conditioner should they occur. The malfunction indication may be by means of signal lights and a manually operable reset control is provided permitting the user to reset the control system. The malfunction indicator and reset control are disposed adjacent the thermostat for facilitated determination of the system operating condition. The control system includes an improved control position for starting of the compressor motor which is arranged to prevent operation of the system in the event of a low power supply voltage condition.