Terminal markings for 3 phase motor
Terminal markings for 3 phase motor
(OP)
I currently have a unmarked motor which is a 3 phase 2 speed single winding type with 6 leads. Does anyone have any idea how to identify the leads to allow for marking. Any input would be greatly appreciated.





RE: Terminal markings for 3 phase motor
RE: Terminal markings for 3 phase motor
constant Hp,constant TORQUE OR variable Torque.All these
motors would have the same # of leads the only difference
would be how they are hooked up 1/2/3/4/5 and 6.
If you know your application,such as pump or fan which would call for Var TQ motor, or a conveyor/crusher which would probably be a constant TQ (2 Star/parallel)for Hi-speed Leads 4/5/6 line 1/2/3 together.for low speed line to 1/2/3 and 4/5/6 separate.By measuring the Ohmic values
of the leads you should be able to identify your phases.
Regardless how you do it,it still a trial and error method.Someone suggested looking at the connections If at all possible and it might save you some time.As for applying any power for these tests I would stay with low voltages and look for balance currents and possible rotor motion.
GusD
RE: Terminal markings for 3 phase motor
one winding or two winding.
IF you have a two winding, the windings are separate which you can easily determine by taking resistance readings between leads. You do not need markings, simply power one set and separately isolate each lead of the other winding - after you determine which speed is which.
If you get resistance between all leads, then you have a one winding. If you have this one, let me know and I'll give more detailed instructions. When you finish:
Low Speed Connection
Leads 1,2,3 are connected to power and leads 4,5,6 are open and separately insulated.
Hi Speed Connection
Leads 6,4,5 are connected to power and leads 1,2,3 are connected together and insulated.
Both variable torque and constant torque use the same connection.
As StarDelta has pointed out there are many strange connections. Hopefully you will have the two separate windings.
RE: Terminal markings for 3 phase motor
To clarify the questions the motor is a single winding motor, but there is no consistancy when reading the ohmic values. Usually three of the six wires will have a lower ohmic reading than the other three but in this case the readings are scattered ( .5 ohm, .9 ohm and 1.6 ohm ). Also the leads are all the same size, with no identifiable difference in color. The motor is intended for use as a fan and is an old spare that was rebuilt in Ciaro several years ago. Prior to my arrival on this drilling rig a brand new motor had been burned up simply because the electricians did not know how to wire the new motor. It's simple L1 to 6, L2 to 4, L3 to 5, then join 1,2,3 together. So now I am stuck with an old spare of questionable quality. It may be best to simply air frieght in another new motor, again any suggestions are appreciated.
RE: Terminal markings for 3 phase motor
RE: Terminal markings for 3 phase motor
For a normal two speed, one winding motor:
If you draw a greek delta, there are leads at each apex and leads half way on each leg.
Between each lead is a common and equal resistance.
Pick any lead and measure the resistance between all other leads. You should end up with two low and equal resistance readings, these should be adjacent leads on your diagram.
Label your first lead A and your adjacent leads B.
The lead with the higest reading should be the opposite leg, center tap lead. However it will be quite close to the the other pair.
So, pick one of the remaining leads and repeat the process.
You now have two sets of leads marked A and B respectively.
As a second check: if you have a surge tester avail- connect one group together and surge test the three other leads - you should get a consistant pattern.
Then: Energize one set, with the other set open and individually insulated - at 1/2 voltage. If it runs at low speed, you got it, otherwise you have an odd one.
Send it to a repair shop. If your're any where near San Diego CA, I can help you.
You will still need to check rotation to get the numbering right. You don't want to have one speed CW and one speed CCW.
Good Luck
RE: Terminal markings for 3 phase motor
http://www.sea.siemens.com/contrlbu/upld/files/p41-46.pdf
etc. for more info
RE: Terminal markings for 3 phase motor