Abstract: A starting circuit for use with single phase induction motors such as capacitor run and capacitor start, capacitor run motors is shown having a triggerable semiconductor (Q1, Q2 and Q3) serially connected to the auxiliary winding (AW) across the power supply (L1, L2). A resistor (RA) is serially connected at (J1) to the main winding (MW) to form a voltage divider to aid in providing triggering current to the triggerable semiconductor. A thermistor (PTC) is connected between the gate and the voltage divider junction (J1). The triggerabIe semiconductor is shown as a triac (Q1) in certain embodiments and as back to back SCRs (Q2 and Q3) in other embodiments. In high current motors the voltage divider resistor (RA) is shown thermally coupled to the thermistor (PTC).

Abstract: An electronic motor protection system is shown having a power supply usable with multivoltage supplies and providing protection from over-temperature conditions caused by various fault conditions. The system also has optional features of a time delay for re-energization and for low voltage protection. The system is mounted on a circuit board and encased in potting material which also locks the two housing parts together. A miswiring feature is also provided to prevent connecting line voltage to the control circuit or sensor terminals.

Abstract: A phase sequence protection circuit is shown in which first and second resistors (R1, R2) and a first capacitor (C1) all having equivalent impedance are connected in a Y configuration and coupled to power source leads (A, C, B) of a three phase power supply, resistor R1 being coupled to phase A, capacitor C1 to phase B and resistor R2 to phase C. A comparator network (12) is connected in line with the first resistor (R1) and, in one embodiment will cause a solid state switch (Q1) to conduct when the phases are out of sequence. In a second embodiment a buffer portion (COMP2) is provided to add switching hysteresis which also reverses the switching logic causing the solid state switch (Q1) to conduct when the phases are in sequence. In another embodiment the comparator network (12") is provided with the buffer portion (COMP2) for switching hysteresis and arranged to cause the solid state switch (Q1) to conduct when the phases are out of sequence.

Abstract: An autotransformer is used to replace the start capacitor in a split phase induction motor. The autotransformer windings are protected by a PTC resistor which also serves to effectively de-energize the auxiliary winding. In a preferred embodiment, efficiency of the motor in the run mode is enhanced by shunting the secondary of the autotransformer with an NTC element. In alternative embodiments a relay coil is placed in series with the auxiliary winding circuit to remove the PTC and the primary of the autotransformer from the circuit when the motor is in the run mode.

Abstract: A split phase electric motor starter and protector are shown having a housing which receives a PTC starter switch and a motor protector and provides various wiring options for connecting the PTC switch and, if desired, a capacitor to a motor depending upon the particular requirements of an application. The housing optionally accommodates a capacitor support bracket.