A soft starter controls the acceleration of an electric motor by controlling the applied voltage. A soft starter also reduces the internal stress of the electric motor by reducing powertrain torque and load.
A soft starter gradually applies voltage and controls the supply going to the motor. There are two types of soft starters:
- Open loop: also known as a time voltage ramp system, allows voltage to increase regardless of motor speed until the full supply levels are reached
- Closed loop: starting voltage is modified according to motor speed or amount of current
By continually controlling voltage output, the soft starter improves the service life of any machine in which the starter is installed.