2 Speed 2 Winding 3 Phase Motor Problem

[errolf]

We currently have a Leroy Somer 3 phase, 2 speed, 2 winding motor which has been rewound. Nameplate details are: 280/85 KW, 415 Volt, 471/158 Amps, 1480/980 RPM, 3Phase, 50 HZ, 315 Frame, Type PLS315VLG4/6B3.
Winding data: 4 Pole Winding:
72 Slot, 36 Coils, 4 Turns per Coil, 1-16 Coil Pitch, 2 Parallel Delta Connection, 6 Leads out, Wire Size 13 x 1.4 mm.
6 Pole Winding:
36 Coils, 3 Turns per Coil, 1-11 Coil Pitch, 1 Star Connection, Wire Size 17 x 1.4 mm.
This motor is drawing excessive current on the 6 pole winding at full voltage no load and appears to have a transformer effect and being influenced by the 4 pole winding in some way, the delta connection on the 4 pole winding is open during the test run of the 6 pole speed.
Can anyone please throw some light on this subject and tell me what is the cause or possible cause? I have never come across this before in all of my years in the motor winding trade. If anyone can help me I would appreciate an urgent responce.

 

[edison123]

1. What is the core length & diameter ?

2. Is each winding single layer winding?

3. How are two speed windings physically arranged ? (side by side or low speed on top layer & high speed on bottom layer)

 

[SteveKW]

I suspect your problem rests in your "2 Parallel Delta Connection" which is a closed loop.

I am a bit rusty on the terms so I may say it wrong... but are you using a 1-4 or 1-7 connection? According to my redesign manual, for a Star conection, a 1-7 is desirable!

The manual descrbes your loop like an oval track for current to flow! To correct it you need to make the path a figure eight. This forces the currents to cancel each other out.

 

[jbartos]

Suggestion: Measuring the motor parameters and comparing them to the motor spec data sheet parameters would reveal whether or not there are no motor internal damages, e.g. turn-to-turn short circuits.