Motor winding identification

Spurred on by this post ( http://www.plctalk.net/qanda/showthread.php?t=26742 )

Can anyone explain how you would go about identifying the windings of a three-phase single speed, 6 lead AC induction motor?
It can be worked out which pairs of leads are the windings with an ohmic check but how do you find the correct orientation of each winding?

I once heard it can be done with a battery and galvanometer... but how?

silva.foxx said:

I once heard it can be done with a battery and galvanometer... but how?

Click to expand...

That we call it as megger test

I'm not referrrrrring to INSULATION RESISTANCE testing.. but to finding correct orientaaaation of windings.

silva.foxx said:

Spurred on by this post ( http://www.plctalk.net/qanda/showthread.php?t=26742 )

Can anyone explain how you would go about identifying the windings of a three-phase single speed, 6 lead AC induction motor?
It can be worked out which pairs of leads are the windings with an ohmic check but how do you find the correct orientation of each winding?

I once heard it can be done with a battery and galvanometer... but how?

Click to expand...

Hi,

This is how you do it....

Step 1. Identify the 3 pairs of windings. This is easy, using a multimeter. Mark the ends A,A, for the first pair, then B,B, then C,C etc.

Step 2. Obtain a LOW voltage A.C supply. Around 10 volts will be sufficient. {Note that this will only work with an A.C. supply, not D.C.}. Connect this supply to the wire A,A. but do not turn on yet.

Step 3. Pick one end of the pair B,B, and connect it to one end of the pair C,C. With the remaining wires (one B and one C) connect to a multimeter set to volts AC.

Step 4. Turn on the supply. Check for a voltage reading on the multimeter. Now please note the following carefully...

The motor windings are referred to as "Starts" and "Finishes". If the connection between B and C is a "Start" joined to a "Finish", you will read a small voltage on the multimeter.
If no voltage is present, then the connection between B and C is a "Start" joined to a "Start".
If no voltage is detected, swap one of the wires at the connection between B and C.

Step 5. Lets say you have successfully produced a voltage..Should be around 4 volts..Where did this come from?? {I dont want to sound like a smart a$$, but this is important} If you get to the stage whereby a voltage is produced, then mark the B wire at the junction with C as B1. Mark the C wire at the multimeter as C1. This will give you the relationship between the B and C wires.

Step 6. The above procedure needs to be repeated for the A,A wires....

{Step 6a. Post back here if you are unsure of the steps outlined above}

Step 7. Join the wires A1, B1 and C1 to make a STAR (in Oz) or WYE (in USA) connection. Apply your 3 phase power to test your motor...Get ready to turn it off quick if something goes wrong!!

Good luck

Ian

IAN

That is perfect! It works... great. It's my new quiz for the workshop guys.

Many thanks.

Good to hear back from you.


This is something that I did not learn during my apprenticeship (training), but learnt many years later when I went back to college as a teacher...

It is something that every electrician should know how to do, but not many do.
Cheers

silva.foxx said:

IAN

That is perfect! It works... great. It's my new quiz for the workshop guys.

Many thanks.

Click to expand...

Not a good quiz test, those that can do this are far beyond the average electrician.

The DC battery test may have pertained to something in your past for DC motors, there is a method for this.

This is something you know or learn in time, not something anyone would know...note: you did not, why put it on a test? If someone knows it they may take your job.

or there is the brave way.................assuming you have found the pairs

connect it in star, you have now either got it right or one winding wrong.
Try a quick power on - it buzzes, swap one pair - it still buzzes - put that pair back as it was and swap another pair - do this until bingo - or no motor lol.

It works because i remember doing once a long time ago

Whoa there horsey!

rsdoran said:

Not a good quiz test, those that can do this are far beyond the average electrician.

The DC battery test may have pertained to something in your past for DC motors, there is a method for this.

This is something you know or learn in time, not something anyone would know...note: you did not, why put it on a test? If someone knows it they may take your job.

Click to expand...

Chill Ron, don't read into this formally. Read "I'll put it on a test" as "Look at this, lads, a cool trick you may never need!" Also, who said my colleagues are only avarage electricians? Let it ride.

Now what if the motor has 9 or 12 leads and 6 windings instead of 3, and all of the wire markings are missing?

Does anyone else know the technique for identifying all 9 leads of a 3 phase 3-winding motor? (In a 9-lead motor, 3 leads are connected internally and are not normally accessible).

Hint: To do it by hand requires about 64,000 tests!

Lancie1 said:

Now what if the motor has 9 or 12 leads and 6 windings instead of 3, and all of the wire markings are missing?

Does anyone else know the technique for identifying all 9 leads of a 3 phase 3-winding motor? (In a 9-lead motor, 3 leads are connected internally and are not normally accessible).

Hint: To do it by hand requires about 64,000 tests!

Click to expand...

well,,hopefully it wouldnt take that many trys,,ill be willing to bet(unless you have murphy working against you) youll find it in many less tries

Fred Raud