10/27/2022 0 Comments Star delta problem pdfOnce the time delay is reached its specified Time, the timer’s auxiliary contacts (KT)(3) in Star Coil circuit will change its position from NC to NO and at the Same Time Auxiliary contactor (KT) in Delta Coil Circuit(4) change its Position from NO To NC so Delta coil energized and Delta Main Contactor becomes NO To NC. When Star Main Contactor (KM1) close its connect Motor connects on STAR and it’s connected in STAR until Time Delay Auxiliary contact KT (3) become NC to NO. This sequence happens in a friction of time.Īfter pushing the ON push button switch, the auxiliary contact of the main contactor coil (2) which is connected in parallel across the ON push button will become NO to NC, thereby providing a latch to hold the main contactor coil activated which eventually maintains the control circuit active even after releasing the ON push button switch. When Star Auxiliary Contactor (1) (which is placed on Main Contactor coil circuit ) become NO to NC it’s complete The Circuit of Main contactor Coil (KM3) so Main Contactor Coil energized and Main Contactor’s Main and Auxiliary Contactor Change its Position from NO to NC. When Star Contactor Coil (KM1) energized, Star Main and Auxiliary contactor change its position from NO to NC. The ON push button starts the circuit by initially energizing Star Contactor Coil (KM1) of star circuit and Timer Coil (KT) circuit. The control circuit consists of push button switches, auxiliary contacts and a timer.Ĭontrol Circuit of Star-Delta Starter (Open Transition) Scheme – Control Circuit of Star-Delta Starter (Open Transition) This provides one third of DOL current to the motor, thus reducing the high inrush current inherent with large capacity motors at startup.Ĭontrolling the interchanging star connection and delta connection of an AC induction motor is achieved by means of a star delta or wye delta control circuit. The star contactor serves to initially short the secondary terminal of the motor U2, V2, W2 for the start sequence during the initial run of the motor from standstill. The Star and Delta are electrically interlocked and preferably mechanically interlocked as well. The control of the contactors is by the timer ( K1T) built into the starter. In operation, the Main Contactor ( KM3) and the Star Contactor ( KM1) are closed initially, and then after a period of time, the star contactor is opened, and then the delta contactor ( KM2) is closed. The main contactor connects the reference source voltage R, Y, B to the primary terminal of the motor U1, V1, W1. The main circuit breaker serves as the main power supply switch that supplies electricity to the power circuit.
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