Soft Start vs. Full Voltage start

Why is it better to use a Soft Start (Solid State) motor starter than a full voltage, across the line starter for large compressor motors?

 

The soft start allows us to slowly bring the compressor motor up to speed which reduces the high inrush current, reduces initial torque and reduces the possibility of belt slippage at startup.

 

For the full voltage, across the line start, the inrush current at startup is 600% of the motors RLA (Running Load Amps) and the initial torque is 180%-300% peak.

 

For the soft start (solid state) motor start, the inrush current at startup is 300% of the motors RLA and 25% of the full voltage starters initial torque.

 

Better for the motor, better for the machine and in some locations, better for the customers power bill.