Motor Starting on the HV side of its feeder transforme

[purplepete]

Gents,
In a project with which I'm involved it is proposed that a squirrel-cage induction motor (1250 HP 3.3 kV) be direct-connected to its dedicated feeder transformer secondary (approx 2,500 kVA) and then started and stopped (running for a week at a time aproximately) by means of the 33 kV circuit breaker on the primary side of the transformer. I am looking for guidance on what to tell the transformer manufacturer (apart from the obvious) and what the impact is on the protection schemes and any other hardware, particularly the coincidence of motor and transformer inrush currets. Can someone direct me to any authoratative writings please? I've Googled but not found much.
Thanks
Peter.

 

[jraef]

I can only say that it is done all the time at lower voltage levels, i.e. large deep well pumps that use a step-up transformer at the surface so that there is less wire weight and voltage drop over the distance to the motor. There are plenty of issues with the transformer magnetizing inrush causing fuses to blow or breakers to trip, but those are all solvable problems.

My biggest concern would be wear and tear on the 33kV breaker; anything at that level is not inexpensive! Most HV equipment is not designed for that kind of duty cycle. Has anyone consulted the manufacturer? If it's new, has this been brought up from a feasibility standpoint with leading equipment mfrs? I would start there.


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