6-Lead Induction Motor - Swap Leads 1 and 4?
6-Lead Induction Motor - Swap Leads 1 and 4?
(OP)
What would be the consequence of inadvertently rolling lead 1 and 4 for example on a 6 lead, wye connected induction motor assuming 1, 2, 3 were the phase leads and 4, 5, 6 were the neutral point.
The new configuration would be 4, 2, 3 phase leads and 1, 5, 6 neutral. This is probably a simple question, but we just received a fairly large motor (8000HP) from the shop that was re-leaded. They didn't mark the leads themselves, only wrote the lead layout on the side of the motor frame where the leads exit.
The new configuration would be 4, 2, 3 phase leads and 1, 5, 6 neutral. This is probably a simple question, but we just received a fairly large motor (8000HP) from the shop that was re-leaded. They didn't mark the leads themselves, only wrote the lead layout on the side of the motor frame where the leads exit.





RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Muthu
www.edison.co.in
RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
The good news... you can certainly figure out the correct leads with a 3-channel oscilloscope.
Channel 1: + = T1, - = T4
Channel 2: + = T2, - = T5
Channel 3: + = T3, - = T6
Now rotate the rotor in the direction of normal rotation and you will see 3 sin waves. If the waves are 60 degrees apart, one of the pairs is flipped.
If the waves are 120 apart and follow the same sequence as your power system, then the rotation is correct. For example if you have A/B/C sequence and you plan to hook T1-A, T2-B, T3=C, then you should see positive peaks of channel 1 followed by 2, followed by 3, followed by 1 etc. If you saw 1, 3, 2, 1, 3, 2 etc then the planned hookup would result in reverse rotation (and you know how to fix that).
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Bill
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"Why not the best?"
Jimmy Carter
RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Is yours a horizontal sleeve bearing motor? I can see that could be more of a challenge.
I'm going to think awhile about what useful you can get out of 45 degree rotation or whether there might be some alternate test for that scenario.
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Take a motor with known correct lead markings.
Apply a voltage and measure current in the following two configurations:
V+ == T1------ T4 ==T2------T5==V-
V+ == T1------ T4 ==T5------T2==V-
(note that === represents external/test connections and --- represents internal wiring identified by end-terminals).
Is there a difference in current measured with same voltage applied?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
The reason is that the three phase windings are arranged something like a b' c a' b c' ... with overlap among adjacent groups. With 3-phase power supply, the phase difference among adjacent groups is 60 degrees.
When we hook it up per the first configration, the phase difference between adjacent groups will be 180 degrees... the fluxes will tend to cancel... in ideal case of complete cancelation of fluxes (not achieved) the magnetics are irrelevant and the current limited only by resistance (high current).
When we hook it up per the 2nd configration, the phase difference between adjacent groups will be 0 degrees... the fluxes will tend to add, the inductance will increase and current decrease.
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
Hook up all three windings in series (ac supply):
V+==T1---T4==T2--T5===T3--T6==V-
A = test as is.
B = test with T1/T4 reversed from above
C = test with T2/T5 reversed from above
D = test with T3/T6 reversed from above
One of the four tests will be significantly different from the other three:
* If test A is significantly different than the other three tests, the the labeling of leads is correct as-is.
* If test B is significantly different than the other three tests, then T1/T4 are labeled in reverse.
* If test C different, then labeling of T2/T5 is backwards.
* If test D is different than the other 3, then labeling of T3/T6 is backwards
All of this assumes we have started by doing a continuity test to verify we at least have the pairs correctly.
None of this will tell you the rotation.
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RE: 6-Lead Induction Motor - Swap Leads 1 and 4?
I used this test (file attached) a few years ago on repaired submersible pumps to identify the lead ends. I'd really appreciate comments thanks.