초록 ▼

A start circuit for an induction motor having a main winding and a start winding includes a sensor of main-winding current. A detector detects the level of main-winding current sensed by the sensor. The start circuit includes a reference generator driven by the level detector and providing a referen

A start circuit for an induction motor having a main winding and a start winding includes a sensor of main-winding current. A detector detects the level of main-winding current sensed by the sensor. The start circuit includes a reference generator driven by the level detector and providing a reference level proportional to an average value of main-winding current. The reference level can vary slowly in accordance with a long-term drift in magnitude of the main-winding current. A switch energizes and deenergizes the start winding in accordance with relative values of a signal of the detector and the reference level, thereby allowing for automatic restarting in the event of a sudden increase of current due to a motor stall.

대표청구항 ▼

A starting circuit for an electric motor having a main winding and a start winding, said starting circuit comprising: means for sensing the magnitude of a current flowing in said main winding; means coupled to said sensing means for generating a reference level which is proportional to an average va

A starting circuit for an electric motor having a main winding and a start winding, said starting circuit comprising: means for sensing the magnitude of a current flowing in said main winding; means coupled to said sensing means for generating a reference level which is proportional to an average value of said main winding circuit, said generating means including reference storage means and compensation means, said reference storage means having a capacitor and a resistor in a charge path for charging said capacitor to a voltage proportional to said average value by a first factor, said compensation means providing an additional resistive charge path for charging said capacitor to a voltage proportional to said average value of main winding current by a second factor larger than said first factor, said first factor being based on a value of main winding current obtained under a locked rotor condition, and said second factor being based on a value of main winding current obtaining during normal rotational speed of a rotor of the motor; means for comparing said current magnitude with said reference level; power supply means for activating said starting circuit after initial energization of said main winding; and switching means driven by said comparing means for terminating a flow of current in said start winding when the magnitude of current in said main winding drops below said reference level, and for initiating a current flow in said start winding when the magnitude of current in said main winding rises above said reference level.