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Soft Starter


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We are having problems using soft starter in a reciprocating compressor application though it works in Fan, Injection Moulding machine.


When we use with compressor, the motor starts in soft mode but after 5-10 minutes the soft starter gets overloaded and motor draws heavy current. We tried 37KW soft starter on 37KW compressor motor.


Would be obliged by any rely on possible causes and corrective measure.


best regards


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Hello bksuresh


It sounds to me as though either you have a mechanical problem which is causing the motor to become overloaded, (independent of the soft starter), or you have a problem with the energy saving function on the soft starter.

Some soft starters come equiped with an energy saving function that is designed to reduce the voltage when the motor is okperating under reduced load. If the voltage is not returned to full voltage quick enough when load is applied, the motor will stall and draw a lot of current. A reciprocating compressor is a cyclic load and I suspect that this could easily be the problem.

Try to disable the energy saver, or use a bridging contactor to short out the SCRs once the motor is up to speed.

Can you give more details on the soft starter you are using? we may be able to offer more assistance dependign on it's type.


Best regards,

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