Answer / sharad

A soft starter is a solid state motor starter that is used
to start or stop a motor by notching the voltage waveform,
thereby, reducing the voltage to each phase of a motor and
gradually increasing the voltage until the motor gets up to
full voltage/speed all at a fixed frequency. The profile of
the increase of voltage depends on the application. The
voltage is reduced and controlled by 3 pairs of back-to-back
silicon-controlled rectifiers (SCRs), which are a type of
high speed thyristor. A soft starter takes the place of a
contactor and can also take the place of an overload relay
in a standard motor starting application.

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