Soft starting a Slip ring motor with the rotor shorted

[Marke]

Hi

I recently came across an article in a magazine where it was claimed that "their soft starter" was able to start slip ring motors with the rings shorted.
The implication is that this particular starter is able to do this while others can not.
You can follow some discussion here

http://www.lmpforum.com/viewthread.php?tid=645

Has anyone seen any data or information to suggest that there are techniques that can allow a soft starter to develop more torque and create less slip loss on a slip ring motor with a shorted rotor?

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[aolalde]

Marke:
One of our customers has several IWRM with the secondary winding short circuited and they start successfully, the acceleration is gradual limiting the starting current . However they start under a ramp Volts/Hertz by a variable frequency driver. May be the “soft starter” referred is in reality a VFD.

 

[DickDV]

It's not uncommon to start wound rotor motors as you describe with SCR based electronic softstarters. But I don't think you will get higher starting torque. In fact, simply shorting the slip rings may well result in too little rotor resistance. It is often worthwhile to evaluate leaving a little resistance in the rotor circuit to improve torque output and then using an electronic softstart to start.

Seems to me that load requirements under starting and accelerating would be the key factor in making this evaluation.