Useful tips|Soft starters / Braking devices

What does it mean if a soft starter is 1-, 2- or 3-phase controlled?

In 1, 2 or 3 phases of the motor supply line the voltage is changed via power semiconductors (thyristors or Triacs), and thus soft acceleration and deceleration of the drive is enabled. The uncontrolled conductors are directly connected to the mains.

Is it possible to reduce the starting current peak of my drive__with a 1-phase controlled soft starter?

No! With a 1-phase control it is only possible to reduce the torque surge. In order to additionally reduce the peak current, a 2- or 3- phase controlled soft starter has to be selected.

Can I softly decelerate my drive (e.g., a pump) with a__1-phase controlled soft starter, too?

No! With 1-phase control only soft start is possible. Controlled deceleration requires a 2- or 3- phase controlled device.

Is it advantageous to replace a star-delta-switch__by a soft starter?

Yes! The motor supply line needs to be implemented only as a 3-pole instead of 6-pole line. There are no current peaks and no sudden torque surges as they appear during the switchover from star to delta, which gives the mechanical system of your drive a longer life and protects the network. No reduced starting torque as in the case of starts with star-connection.

What are the advantages of soft starters?

They are easy on the mechanical components of the drive and protect them. Pressure surges in pump systems can be avoided. The electrical network is protected (no current peaks; negligible voltage dips). Easy to operate and maintenance-free. Can be retrofitted into existing plants without any problems. Cabling is simpler than in the case of star-delta-starting.

How long is a circular saw blade allowed to decelerate after__switching off the saw?

According to the applicable standards for the safety of wood working machinery (DIN EN 859) the deceleration time must be shorter than 10 sec..

Can I operate a sliding-rotor motor (crane drive)|on a soft starter?

Yes! With single-phase controlled SAS-devices it is possible to achieve good starting characteristics. The two uncontrolled phases generate a magnetization of the motor which, immediately after switching the system on, pulls the rotor out of the braking position.

Can I operate a brake motor on a soft starter?

Yes! Without any problems, by means of a single-phase controlled SAS-device. The motor terminals to which the braking coil is connected, has to be connected to the uncontrolled phases on the soft starter (terminals 2T1 and 4T2). In the case of 2- and 3- phase controlled soft starters the braking coil has to be separately controlled.

Are soft starters and braking devices, as regards the emitted__interference (EMC), in conformity with the standards?

Yes! The devices meet the product standards for electronic motor controllers (DIN EN 60947-4-2).