Abstract: An improved control circuit for a single-phase two-speed motor as used in a hermetic refrigerant compressor which includes start assist means is disclosed. In the preferred aspect of the invention, a start assist means is disposed between the start capacitor means and the run capacitor means for providing a discharge path for the run capacitor means into the start capacitor means after the motor is deenergized.

Abstract: A control circuit for a two-speed single-phase motor as used in a hermetic refrigerant compressor which includes means for preventing welding of the start relay contacts of the start relay means by electrical discharge from the run capacitor. In one aspect of the invention, a discharge path is provided for the run capacitor by switches and auxiliary contactor means. In another and preferred aspect of the invention, a negative temperature coefficient thermistor is used in series with and between the start capacitor means and the start relay contacts for limiting the current to the start windings from a source of power and for limiting the current discharged into the start capacitor means from the run capacitor after the motor is deenergized.

Abstract: The disclosure describes a refrigerant compressor of the type driven by a motor capable of operating at a low speed and a high speed, the motor including first, second and third stator coils. First, second and third temperature sensors are located adjacent the first, second and third stator coils, respectively, for detecting any change in temperature of the coils. If the temperature of any of the stator coils exceeds a predetermined value, a control device operates a switch in a pilot circuit that turns off the motor before damage from excessive heat can occur. A unique contactor assembly utilizing both electrical and mechanical interlocks interconnects the stator coils to provide two speed operation.

Abstract: An improved circuit for protecting the motor of a refrigerant compressor includes first and second magnetic contactors which are connected between a source of three-phase AC voltage and the compressor motor. The contactors are normally operated simultaneously so that each of the contactors is periodically opened and closed in accordance with the demands for operation of the compressor motor. If one of the contactors fails in the closed position, the other contactor will open to protect the compressor motor. This result is accomplished through use of a high impedance relay coil provided in parallel with contactor switches in the common line to the compressor motor and a normally closed switch actuated thereby in the control circuit, whereby if one of the contactors should stick closed, the high impedance relay coil can be energized to open the normally closed switch and prevent compressor motor operation and possible damage to the compressor motor.

Abstract: The disclosure describes a refrigerant compressor of the type driven by a single phase motor capable of operating at a low speed and a high speed, the motor including a run winding, a 2-pole start winding and a 4-pole start winding. First and second temperature sensors are located adjacent the windings for detecting any change in temperature of the windings. A current transformer is used in combination with the temperature sensors to protect the motor windings. If the temperature or current conduction of any of the windings exceeds a predetermined value, a control device operates a switch in a pilot circuit that turns off the motor before damage from excessive heat or current can occur. A unique contactor assembly utilizing both electrical and mechanical interlocks interconnects the windings to provide two speed operation.

Abstract: The disclosure describes a refrigerant compressor of the type driven by a motor capable of operating at a low speed and a high speed, the motor including first, second and third stator coils. First, second and third temperature sensors are located adjacent the first, second and third stator coils, respectively, for detecting any change in temperature of the coils. If the temperature of any of the stator coils exceeds a perdetermined value, a control device operates a switch in a pilot circuit that turns off the motor before damage from excessive heat can occur. A unique contactor assembly utilizing both electrical and mechanical interlocks interconnects the stator coils to provide two speed operation.