In addition to the benefits of soft start and soft stop, which improve the operating life and efficiency of your equipment, the STO also protects your three phase motor and load from damage during operation.
With built-in motor overload protection, the STO continuously monitors the motor current and then calculates the expected temperature. The user sets the motor trip class via the front panel and the STO will trip when the calculated temperature reaches a set value, preventing operational overload and ensuring user peace of mind.
Further benefits of using the STO soft starter include the bypass overload protection that safeguards the starter from severe spikes in current. The starter also monitors the time taken to start and will trip if the motor cannot start within the allowed time, protecting against stalled loads.
Suitable for Squirrel Cage Motors the STO soft-starter works by gradually applying reduced voltage, essential in protecting the motor from overheating causing winding damage (AC Motors that start at full voltage can experience 5 to 9 times their nominal current).
The STO has several adjustments for more control:
- Current ramp (soft start).
- Current limit.
- Motor full load current (FLC).
- Soft stop.
- Excess start time.
- Motor trip class.
- Start current.
Why use a soft starter?
A soft starter is a device which controls the acceleration of an electric ac motor by means of controlling the applied voltage.
Without this control the interaction between the rotating magnetic field flux and the rotor winding flux will result in a high rotor current as torque is increased. By the time the motor reaches full speed, a current greater than the rated current will be drawn resulting in overheating and likely motor damage. To prevent this, a soft starter is needed.