DEVICE FOR STARTING THREE-PHASE SQUIRREL-CAGE INDUCTION MOTOR FROM OFF-LINE COMMENSURABLE- POWER SUPPLY Russian patent published in 2004 - IPC

FIELD: electrical engineering; starting industrial, household, and farming motors. SUBSTANCE: proposed device for starting three-phase squirrel-cage induction motor connected to off-line commensurable-power supply has magnetic starter whose power contacts are used to connect three-phase induction motor to off-line power supply. Connected to first lead of magnetic starter coil are first leads of second magnetic starter coil and of time relay coil. Their second leads are interconnected and connected through making contact of current relay and breaking contact of time relay to point of connection of START button and interlocking making contact of second magnetic starter. Primary winding of current transformer is connected in series with phase leads connecting motor to supply mains, and secondary winding of this transformer is connected to current relay coil. Bank of starting capacitors is connected between power contacts of magnetic starter and motor leads a, b, c through power contacts of second magnetic starter. Bank of starting capacitors will provide for reactive power during motor starting so as to enable starting motor from this bank of capacitors thereby reducing load on off-line power supply. As soon as motor gains speed, current relay breaks contact in magnetic starter coil circuit to deenergize these coils with the result that bank of capacitors is disconnected from motor. EFFECT: reduced mass, size, and cost of power supply for same starting characteristics of motor connected to ac commensurable power supply. 1 cl, 1 dwg