VFD for Slip Ring Induction Motor

How and why has the requirement arisen, please?

Why wouldn't it be possible?

Then tell me what are the work i need to carried out in Motor circuit to connect with VFD...

Follow the connection details given in the manual that came with it?

Dear Mr.PWSlack,

Whether VFD manual or motor manual. In VFD manual it has not given. If you any link, update it..

the stator is same as normal induction motor just the rotor is powerized by the 3 phases and the increase/decrease of the rotor resistance changes the motor speed .

i suggest you to change the rotor , so you can use the vfd with it .

Dear Mr.sohail0110,

Pl. refer post No.10, mere changing rotor alone is not sufficient. Cooling of Motor and need of Insulation for bearing on non-drive end to avoid Re-circulation of shaft current is not accounted by you.

DHAYANANDHAN.S

fire it up!

this may help you

http://www.zone4info.com/search?query=Slip+Ring+Induction+Motor

You know, posting a link to a search engine in a thread that is SPONSORED by a search engine is actually fairly rude to our generous hosts.... And not all that helpful by the way.

If you're planning on shorting the rotor windings and introducing the VSD in the stator supply, don't!

A slipring motor is usually used for high inertia loads. Shorting the winding will most likely result in the motor stalling and eventually burn the rotor out.

You can run the motor up to speed as normal and then introduce the VSD in to the stator supply.

Dear Mr. r.baabuu,

You can not and SHOULD NOT put an ordinary Induction Slip Ring Motor in to A VFD Application, for the following reasons.

1. At Lower Speed the air flow for cooling will be reduced, hence winding heating will increase and temp. rises more than normal rise. A seperate air-blower is to be fitted

2. The bearings provided for Non-VFD motor will NOT have Bearing Insulation or Insulated Bearing, which is a must.

3. Whether the Transformer (if 11 KV is stepped down and used) is suitable for VFD application is to be checked.

DHAYANANDHAN.S

ASSuming that you are referring to a Wound Rotor Induction Motor and not a Synchronous Motor with slip rings, then it is possible and very viable. You must short out the slip rings ON the rotor to avoid instability in the rotor circuit as the brushes wear. That can mean rebalancing the rotor to ensure the shorting bars that you add are not causing an imbalance, but the importance of that is dependent on the size and speed of the motor to some extent. You also must use a very good sensorless vector drive that can attain a fairly stable degree of current regulation, and not all drives are created equal. If you stick with the major brands you will be fine, but do not use the cheap copycat drives, because the usual place where they cut corners to make them cheap is in the development of more complex control algorithms and sensing systems, both of which are crucial for this application.

All that said, this is not a simplistic application and if you are as unsure about it as it appears from your questions, you should consider finding and aquiring the services of an experienced expert in your area.

Dear All,

I am planing to start the Motor as a slip ring Motor without changing it's rotor connection by using Star Delta Starter and When the Motor will reach it's Full load RPM then i will switch over it to VFD mode.

Now, Give your suggestion on the above points..

Star-Delta Starter for a Slip Ring Motor? I am baffled!

"Replying to Comment by electricalexpert65: Star-Delta Starter for a Slip Ring Motor? I am baffled!"

Baffled is an understatement! I think this is further evidence that the OP should bow out and turn this over to a professional!

Although, hmmm.... As a mfr of VFDs and controls, I like the idea of creating a situation where they become consumables!

R.baabuu, please let me know where you are so that I may continually sell you replacement VFDs and Start-Delta contactors! I can always use the repeat business...

dear r-baabuu

what is the rating of your slip ring motor?