With a built-in bypass function and simple operation, the STB range from CD Automation offers a compact, cost effective solution to start and stop 3 phase AC motor control.
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.
Suitable for Squirrel Cage Motors the STB006 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).
Three adjustments can be made on the STB006 soft starter:
- Initial start voltage (initial torque).
- Soft start ramp time (ramp up).
- Soft stop ramp time (ramp down).
No feedback is needed from the motor and Ramp-up and Starting (Initial) Torque is set by the operator from the STB’s front panel.
While soft starters operate continuously to control and protect the motor, the soft starter power section may be bypassed once the soft start is complete. This built-in bypass function provides greater operating efficiency and reduced heat in the enclosure (eliminating additional enclosure cooling).
In addition, the STB range has a kick start facility. The kick start allows the motor to draw greater current at start-up and create additional torque to break away a high friction load, useful in starting blocked pumps etc. This feature is user selectable between 100, 575 and 300mS.