Texas Instruments Corporation

Joseph G Nield, Jr

John R D'Entremont

Radi Pejouhy

Kerry J Denvir

Alfred Raulino

James T Racine

Beggs, Louis C

An electronic motor protection system which protects electric motors against various fault conditions such as over-temperature (,) of the individual windings of the motor and low voltage (,). The system has a power supply compatible with 24, 120 or 240 VAC input voltage using only two input terminals. According to a first embodiment, line voltage is inputted to a transformer (T,) while the combination of a zener follower (Z,, Z,, Q,) and series regulator (U,, Q,, Q,) provide independent DC voltage supply levels or voltage rails (VR,, VR,) for control circuitry over a wide range of input voltages. A dead-band voltage range is provided by a circuit section (,) which works in conjunction with a 240 volt, low voltage cut-out circuit section (,) to prevent the possibility of chatter in 240V motors and excessive voltage from being applied to 120 volt motors. The motor is protected by means of an output relay (K) being de-energized upon detection of a fault condition which energizes an adjustment circuit (,) to stabilize the load seen by the power supply transformer. According to a second embodiment input voltage level is detected by comparator circuitry (U,A) in the secondary side of a transformer (T,) which switches contacts of a double pole, double throw relay K,to switch first and second primary transformer windings (TP,, TP,) from a parallel configuration when exposed to 120 VAC to a series configuration when exposed to 240 VAC.

Electronic motor protection system

A thermally actuatable auxiliary switch (10, 10', 100) used with a refrigerator compressor system (60) has a generally U-shaped bimetallic element (12) mounted at one end on a base plate (16, 16', 102) and with a movable contact (28) mounted on the high expansion side (12a) of the bimetallic element in alignment with a stationary contact (32) mounted on a stationary contact support (18, 18', 116). A thermal generator (34) in the form of a PTC pill (36) wire-wound resistor (28), or other electrically energizable heater or in the form of a discharge tube (60e) of a compressor, provides heat to the bimetallic element (12) causing it to deflect after the solid state starter (50) has switched to its high resistance state to switch out the solid state starter while the compressor motor remains energized.

Thermally actuatable auxiliary electrical switch apparatus

Electrical terminal pins (start, main and common) mounted in a glass header to provide electrical connection to a compressor motor are shown with a motor protector disposed on one of the pins in such a fashion that opposite-direction-oriented right angle female flag quick connectors are required for the start and main terminals, thereby avoiding the possibility of miswiring the terminal pins. The opening temperature of the motor protector is adjustable and the protector has a fail safe mechanism to avoid subjecting the motor to overtemperature conditions.

Plug-on protector for compressor motor

A motor protector having a thermostat metal element thermally coupled to an electrical motor in a refrigerator compressor motor system has a heater responsive to motor current thermally coupled to the thermostat metal element and has an improved component arrangement to provide locked rotor and ultimate trip protection for the motor without requiring calibration of the operating temperature for the protector after assembly or after incorporation in the motor system.

Protected refrigerator compressor motor systems and motor protectors

A miniature motor protector particularly suitable for low current applications has a generally rectangular parallelepiped configured metallic housing open at the top having a bottom wall and side walls extending upwardly therefrom, the side walls having a flange forming a ledge portion at their free ends extending around all four sides with at least two opposed flanges have an extended portion to permit them to be bent to clampingly engage an element received on the ledge. An electrically insulative gasket is disposed on the ledge with a plate-like element having a selected electrical resistance placed on top of the gasket. The extended flange portions are bent over the gasket and plate-like element to clampingly engage them. The plate-like element is formed with a first switch element mounting portion, a second heater portion and a third support portion adapted to engage the ledge on all four sides. A second switch element is mounted on the bottom wall of the housing with one of the switch elements including a cantilever mounted snap-acting thermostatic member adapted to move into and out of engagement with the other of the switch elements upon selected thermal conditions of the thermostatic member.

Growing community of inventors

Cumberland, RI, United States of America

Joseph G Nield, Jr