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Identifying Induction Motor Terminals

10/03/2011 12:26 AM

I would like to know how to identify connecting terminal U1-U2, V1-V2, W1-W2 of 3-phase induction motor if I have no labeling tag.

I am confused about the in/out connections.

Please reply with solid reasons/tests...

Thank you!

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Anonymous Poster #1
#1

Re: induction motor

10/03/2011 1:03 AM

There is only 2 3 phase combinations RYB or RBY.Go ahead.

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#2
In reply to #1

Re: induction motor

10/03/2011 1:09 AM

My question is how to determine in and out of each phase not the phase sequence

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Guru
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#3

Re: induction motor

10/03/2011 1:47 AM

Please use the CR4 private mail system and send a message to

electricalexpert65

He has written an excellent paper on this. If you ask nicely, he may give it to you.

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#4
In reply to #3

Re: induction motor

10/03/2011 1:50 AM

You beat me by 3 minutes!

His posts can be searched also.

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Guru

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#10
In reply to #3

Re: induction motor

10/03/2011 7:02 AM

KVS! Thanks for the compliment! I will surely reply the OP in this forum iteslf.

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Guru

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#5

Re: induction motor

10/03/2011 1:51 AM

I think you mixed up with in/ out as well. First with multimeter identify three windings and separate them. First "star connect" assumed three winding as U1, V1, & W1. Use low rating MCB and try to rotate motor. If MCB trips, interchange U1 with U2 and repeat the test. Still MCB trips, change back U1 & U2 and now try with V1 & V2; the other method is open the motor and identify in & out connections. One more method is apply low voltage DC and identify North pole south poles of each winding and separate inner & outer connections. All the best!

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Subramanyam
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#6

Re: induction motor

10/03/2011 2:34 AM

very simple dear....

first open all six connections

just take continuity tester take one terminal out of six say V1 and check continuity in which you get that's V2 same prosses for all......

or

give singal phase to one terminal say V1 and check return supply where you get it that's V2

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#7
In reply to #6

Re: induction motor

10/03/2011 2:43 AM

déjà moo?

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#17
In reply to #7

Re: induction motor

10/04/2011 2:53 AM

Hi Kvsridhar,

Good answer! Straightforward and to the point plus the photo helps to emphasise the message!

I think this must be one of the sites most popular questions and am constantly amazed by the number of replies that members post which demonstrate their inability to grasp the OP's question.

Today I see the normal good replies (e.g. Electricalexpert65) and also a new version from Yuri.B which is also a good method but I have a recommendation - can we not put this question into a FAQ section with the correct answers which is easy to locate. Yes, I do know there is a section for searching the Forum or all of CR4 but this appears to be beyond some of our members.

I am not trying to distract from the subject but believe that not only this question but also a number of other frequent questions together with their good answers belong in a FAQ section. I would think that a panel of moderators (including Electricalexpert65) could provide a control over the answers to ensure that only the correct, safe methods are given as answers.

Just a suggestion!

Regards to all.

Keith

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#18
In reply to #17

Re: induction motor

10/04/2011 5:07 AM

Hi Keith,

Nice isn't it? It was the "very simple, dear..." that triggered it. If you see this whole thread, there are experts like EE65, Yuri, kvsubramaniam and then we have these who are so smug in their ignorance. Must be nice.

As you say, most people can't be bothered to search. Why bother, when it is easier to post, and some idiot like me will tell where to go for the answer, if not give it already?

One of the moderators (Savvy ... was that you?) gave an excellent post on 'How to search CR4' or something like it. To no one's surprise, only the experts who never have to search contributed, asked questions, gave suggestions etc. Not one newbie came and said that he/she has been helped by that thread.

So.....i am all for a band of experts, but am not so sure if it will be successful. i am all for it though.

Good thoughts anyway, thanks.

PS: i almost overlooked the VERY important point in your post... the potentially LETHAL wrong answers given by some ignoramuses (ignorami ?) wallowing in their ignorance. These are usually pounced on by the experts, but you are right...they shouldn't be allowed to appear in the first place !!!

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#21
In reply to #17

Re: induction motor

10/04/2011 10:02 PM

Keith,

After reading some of the posts in CR4 and other similar forums online, I could not agree with you more. There is two sides to this situation:

1. The experts get tired of always answering the same questions so they start referencing previous answers. This is fair and understandable. The danger is that this method eventually turns the forum into a "wikipedia style" website and you loose that sharp interaction with the people whose knowledge make really cool things happen every day.

2. There are great answers that have already been posted and people deserve to know about them. The person in doubt should at least make a small effort of searching through the forums. Perhaps someone already not only answered his question but also answered questions that will come up in the future.

Experts should be careful not to reference every answer to the search bar-on the other hand-great answers should be resurrected by guiding the person in doubt back a previous discussion. It's a balance.

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#8

Re: induction motor

10/03/2011 6:41 AM

Use CONTUNITY option in multi-meter to find the U1&U2, V1&V2 AND W1&W2.. since we have only 6 terminals..

when u identify the terminals, find in the name plate wether it is given STAR connected or DELTA connected motor...

if not given...

if u want STAR connection, SHORT the U1,V1,W1 OR U2,V2,W2... at last u will have 3 terminals.

if u DELTA connection SHORT U2-V1, V2-W1, W2-U1... at last u will have 3 terminals....

hope it is clear...

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#9

Re: induction motor

10/03/2011 7:01 AM

i) With a multimeter or continuity tester, you can segregate three sets of windings. Can't you?

ii) Now, assume one set of windings to be, say, winding "U" and also, designate its terminals as assumed "U1 & U2".

iii) Take a 9V Cell; Connect + ve of Battery to the assumed "U1" preferably thro a push-switch and - ve to the assumed "U2".

iv) Connect a zero centred galvanometer, to another set of winding, say winding "V" such that the assumed "V1" is connected to the + ve terminal of the galvanometer and the assumed "V2" to the - ve terminal of the meter.

v) Now, when the switch is pressed, the zero centred galvanometer would deflect in the positive direction, if the assumed "U1, U2, V1 & V2" are correct.

vi) Else, if the deflection is on the negative side in the galvanometer, change your assumptions for either one of the winding (That is may be the assumed U1 can be U2 and the assumed U2 is U1 . Or keep the assumptions for U winding as it is and reverse it for the V winding (that is assumed V1 is V2 and assumed V2 is V1).

vii) Repeat this test for applying voltage to other windings and confirm your terminal assumptions.

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#22
In reply to #9

Re: induction motor

10/06/2011 11:38 AM

Spot on! When I was young and green behind the ears we used to call it a Flick Test.

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#23
In reply to #9

Re: induction motor

04/17/2012 2:13 PM

If I don't have a galvanometer what instrument that i use? or can I use multimeter?

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#11

Re: Identifying Induction Motor Terminals

10/03/2011 8:34 AM

Just take continuity tester

you will find 3 seperate windings one with U1 - U2

second with V1 - V2

U1 V1 W1 thhird with W1 - W2

o o o

W2 U2 V2

o o o

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#12

Re: Identifying Induction Motor Terminals

10/03/2011 12:48 PM

Connect alternatively 2 windings in series to a 12V AC (or 24V AC) source. Measure induced voltage in the third winding.

If the 2 windings are connected : beginning-end-beginning-end (end-beginning-end-beginning),

then currents in the 2 windings add and voltmeter senses an induced voltage in the third winding.

If the 2 windings are connected : beginning-end-end-beginning (end-beginning-beginning-end),

then currents are cancelled and there is no voltage induced in the third winding.

When you find all ends and beginnings you can connect the motor correctly.

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#13
In reply to #12

Re: Identifying Induction Motor Terminals

10/03/2011 10:13 PM

For a cold test, a nice post by electricalexpert65, but if one wants to test with applying power, then follow the post by kvsubramanyam. I do the same practice.

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#15
In reply to #12

Re: Identifying Induction Motor Terminals

10/04/2011 2:38 AM

GA. I never thought of this. I see a good logic in this method; I shall try. Thanks a lot.

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#14

Re: Identifying Induction Motor Terminals

10/04/2011 2:21 AM

Thanks to everybody;

:)

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#16

Re: Identifying Induction Motor Terminals

10/04/2011 2:47 AM

Hi One & All,

Here is the a drawing that should help you:

Best luck and let us know how things come out.

BEN

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#19

Re: Identifying Induction Motor Terminals

10/04/2011 7:18 AM

Ben, this is a connection drawing for a two speed dahlander motor. The Topic opener asked for U1-U2, V1-V2, W1-W2 . This tells us he has a one speed motor.

Connection diagrams are highly different !!!

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#20

Re: Identifying Induction Motor Terminals

10/04/2011 2:20 PM

Since you want solid reasons, contact the motor manufacturer

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Anonymous Poster (1); ben1son1 (1); Dobi (1); electricalexpert65 (2); harry potter (1); jessie (1); kedar.231288 (1); Keith Grewar (1); Kombat_Technician (1); kvsridhar (3); kvsubramanyam (2); mmofu (1); mohsinhamid (1); Signode (1); Tornado (1); vargaalex (1); Yuri B. (1); zamanengineer001 (2)

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