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.