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Insulating the motor shaft

Insulating the motor shaft

Insulating the motor shaft

(OP)
Hello All,

I'm currently working on a high speed synchronous traction motor that requires an insulated bearing (its been specified by the client who also makes the drive). The problem I face is that I cannot purchase the required insulated bearing off the shelf(SKF tells me its too small and also that they have discontinued their ceramic hybrid bearing range for this size - 6206). Whilst I am sure other bearing manufacturers may have a solution, I was told by one of the SKF techies that I might be able to insulate the shaft journal myself with some type of coating and then utilise a standard bearing. Has anybody heard of a solution for a small bearing like this? If so, any advice on how to do this?

Many Thanks

RE: Insulating the motor shaft

You should consider the following:

If you want to cope with certain common mode voltage problems of the drive by insulating the rotor, you not only need an insulated bearing, but also an insulation to the mechanical load you are driving. As this tend to be difficult, insulating a bearing of the motor might provide no benefit.

RE: Insulating the motor shaft

Uwe is absolutely right. It all depends on what the motor is driving. The 6206 sounds very small for a traction motor. Is this for a colf cart or a similar system?

If that is so, and the system voltage is correspondingly low (say in the 24 - 110 V range) then the risk you run without an insulated bearing is nil. It is when you get into the 400+ voltage range that you get problems with EDM in the bearings.

Anyhow, there are hybrid bearings available for those shaft sizes. But you will probably find a Chinese supplier. I got a mail from one today, and I expect to see many more.

A shaft grounding system works very well with these low-power motors since the rotor voltage is mainly capacitively coupled.

 

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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