Sometimes, an original winding need to be redesigned

Sometimes, an original winding need to be redesigned.

Why?

Here is an example.

It is about the 4-pole motor of 200 kW; 400 V; Delta connected ( see the photo of nameplate).

Original winding data are:

- double-layer lap winding,

- pitch 1-14,

- 60 slots,

- 4-Delta connection,

- 12 groups of 5 coils,

- 6 groups with 7,8,7,8,7 t/c and 6 groups with 8,7,8,7,8 t/c.

Motor has a repetitive premature failures despite the fact that average lifetime of such a motor should be about 30 years ( with regular maintenance).

At first glance the cause is obvious.

It is weak design from start because of two things:

- excessive value of volts per coil ( approx. 85 Volts) caused with 4D connection,

- different numbers of turns per parallel path: 37 and 38 turns/path will cause a circulating currents and overheating a half of parallels paths.

If the manufacturer's data are repeated during repair, whether the guarantee can be requested or given?

What should be done in such a case?

First of all, send us all the core & slot dimensions in order to check the core capabilities and find out whether or not an option with two circuits is possible..

If there is a possibility, then you should get approval for the redesign from customer.

SOON: Another example of bad manufacturer's design.