Soft starter 1

[zaza123]

What will happen if you run a Synchronous motor with Softstarter on No load to check the direction of rotation. we did that & the Motor Tripped on Overspeed as no load was connected to it.
Is this behaviour of Syn motor alright

 

[LionelHutz]

Sounds odd to me. A synchronous motor does not overspeed when the load is removed.

Does the soft-starter have a bypass contactor? It really should for a synchronous motor but you can get away without one if the motor always has a load.

The synchronous motor will run with a very capacitive or leading power factor. The soft-starter to not fire the gates at the right time for this condition and the motor basically began coasting. The soft-starter might have just flagged this as an overspeed.