Terminal markings for 3 phase motor 4

[cbrocky03]

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.

 

[stardelta]

Are there any distinguishing features between the leads ie, 2 groups of different colours that could indicate the 2 speeds? Checking and identifying circuits between the leads wont help owing to the possibility of reverse phases and I have seen many examples of this type of motor that have burnt out owing to being incorrectly fed. The European spec for lead markings for this type of motor is 1u 1v 1w, for the slow speed and 2u 2v 2w, for the fast. To run slow, feed the 1`s and leave the 2`s open. To run fast, feed the 2`s and connect the 1`s together. This applies to Tapped or Pole Change windings,2&4 4&8 pole etc (series delta parallel star-star,and series star,parallel star-star intercoil connections) and the much more complicated PAM designs 4&6 6&8 pole. Last time we came across this problem a customer had removed leads from the terminal block and not marked them. We gave up on the trial and error method as it was taking too long and proving inconclusive. We finaly resolved the problem by resorting to undoing the intercoil connections, identifying the winding design, and tracing the leads back into the winding. This we decided was the only way we could be 100% sure we were correct as we had to guarantee it! This is not however a method I could recommend to someone unfamiliar with winding design and rewind techniques. My suggestion???....If its critical plant get it into a competant shop who are prepared to guarantee the job.

 

[GusD]

As I understand you have a 2 speed motor with a single winding and 6 unmarked leads out.Your motor could be a
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

 

[acmotorengineer]

there are generally two common types of two speed, AC induction motors:

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.

 

[cbrocky03]

First of all Thank you for the replie's.
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.

 

[stardelta]

Another possibilty, albeit a small one. Its looked on as good practise when carrying out a rewind to bring the 3 winding starts out of the winding on one side and the 3 finishes on the other side. Maybe the 3 leads for each speed have been brought out of the winding on opposite sides. If this is the case its a good starting point for the trial and error method and I can devise some intructions for you with regard to correctly connecting and supplying it. If your considering replacing the motor, and its relatively large in terms of Kw/HP I would be tempted to obtain some repair cost quotes first, explain the problem with your repairer and get his views. Bear in mind 2-speeds have a cost premium over single speed items and are not always available off the shelf, certainly here in the UK anyway! Another 2 things to consider if replacing it.....You mentioned a drilling rig, is the motor explosion proof and does it HAVE to be a 2 speed?

 

[acmotorengineer]

the .5 and .9 ohm reading makes sense, however the 1.9 does not - you may have an odd one. I would expect 1.1 ohm for the high reading between leads. Have you checked the motor to see if it is OK - i.e. Hy Pot, Meg and Surge?

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

 

[jbartos]

Suggestion: Visit

http://www.sea.siemens.com/contrlbu/upld/files/p41-46.pdf

etc. for more info

 

[induction]

It really needs to have the conection pulled up and checked you could tell what the conection is be looking at the horse powers and speeds but lighting it is possible but I would not recomend it. You can determine the possbilities and test it on 1/3 voltage it would not damage it but it would be a hit or miss game.