Dear all,
It seems to me that slip recovery drives (for wound field induction motors), although favourable regarding efficiency, still face troublesome market acceptance. Can anybody tell me whether or not these machines have potential disadvantages regarding maintenance and reliability?
And where can I find manufacturers of static Kramer or static Scherbius cascade slip recovery drives suitable for MW power rating applications?
Regards, Arie Mol, NL

I really can't comment on their disadvantages, but they are rather popular with cement manufacturers over here, most have them installed on atleast the pre-heater (raw mill) fans.

A popular Indian manufacturer who supplies them in MW rating applications is:

Larsen & Toubro Ltd.
Control & Automation Unit,
Automation Systems Centre,
EL-200, TTC Electroncs Zone,
Shil-Mahape Road,
Navi Mumbai, Maharashtra - 400701,
INDIA.
Tel: +91 (22) 27916344, 227683511, 7901401 ext. 344
Fax: +91 (22) 27611590
E-mail: SrikantC@asc.ltindia.com
Web: http://www.automation4me.com
Contact: C. Srikanth - Head - Project Execution (West)

Regards,

Aditya

Hi Arie,
Small world, it's been a while !
I have done some work on large 6x slip recovery drives.
The propblem was at near full speed, the slip speed is low, and it excited low frequency torsional osscilations of a vertical high voltage 6 MW sewerage pump motor.
Cable connections were flexing badly and the terminal box came apart but not short circuits occured by luck.
The flexible element was the motor stool.
It was impossible to sufficiently increase the stiffness of the stool to avoid all the possible combinations of slip speed harmonics and motor speed harmonics.
Reducing the torsional stiffness was proposed but not taken up.
They speed limited the pumps, which is an operational problem.
So in a nutshell, they are dynamically very difficult to design for smooth running.
Cheers

John
Tensor Systems Au

Hi John, good to hear from you, indeed the world is getting smaller each day. I have not yet come across such a case as you described but it is valuable to keep it in mind. Thanks for reply!
Arie Mol
Rotating Equipment Consultant
NL