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3ph Motor Direction of Rotation

09/03/2017 8:02 PM

If i know the direction of rotation of the motor, how can make the right sequence of connection which lead to the correct direction of rotation ??

I have to know the sequence without running the motor.

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#1

Re: 3ph motor Direction of Rotation

09/03/2017 8:17 PM

Is the motor a real motor and hence you have the ability to look at the motor terminal box and see what phases go to what terminals?

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#3
In reply to #1

Re: 3ph motor Direction of Rotation

09/03/2017 8:28 PM

I need to connect the motor to the power supply, and i've to arrange the 3ph cables to the motor terminal to make the right direction of rotation.

And if i can know the sequence of the power supply, how i can know the sequence of motor terminals ??

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#6
In reply to #3

Re: 3ph motor Direction of Rotation

09/03/2017 9:47 PM

The power cables or their connections should be marked, the motor terminals, motor terminal nameplate or motor instruction manual should show phase marking connection to follow for forward direction.

This is a good start, but even that is no guarantee as I have had 11kV network phase wiring miss-wired and hence the phase rotation was backwards.

The only true way to be sure is to use all the information you have at hand, and a phase rotation meter if you have access to one, and then monitor the motor shaft direction the first time you turn the motor on.

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#15
In reply to #3

Re: 3ph motor Direction of Rotation

09/04/2017 10:51 PM

When I used to rewind 3Ph motors, I used numbered wire lead cables with a three wire Delta configuration that 1,2,3 were wired to the three phases A,B,C. The power entrance panel should have three cables, one bare, one w/red tape and one w/blue tape and should enter the main circuit breaker in that order, left to right. You should be able to trace the wiring your working with and mark the phases. If all the phases are wired properly the motor should rotate CW. Then if it doesn't switch two wires around. If you are going into a VFD then it probably doesn't matter anyway because the output is usually a controlled square wave. This is for a one time event otherwise spend the money and get the meter.

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#16
In reply to #15

Re: 3ph motor Direction of Rotation

09/04/2017 11:16 PM

I meant 3 wire Y configuration but the delta would have the same phase order on a three wire motor lead.

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#2

Re: 3ph motor Direction of Rotation

09/03/2017 8:20 PM

..."A phase rotation meter, through the use of its six terminal leads, compares the phase rotation of two different 3-phase connections. Three leads, labeled "A," "B," and "C," are connected to the test unit's side labeled "MOTOR." Three other leads are labeled the same but are connected to the test unit's other side, which is labeled "LINE." The meter also has a zero-center voltmeter, with one side labeled "INCORRECT" and the other labeled "CORRECT."

First, you "zero" the meter per the manufacturer's instructions. Then you position the meter's selector switch to "MOTOR" and connect the three MOTOR leads to the motor's leads. Finally, you hand-turn the motor's shaft in the desired direction while watching the voltmeter, which immediately will swing to the CORRECT or INCORRECT direction. A special note: Although the needle will swing in the opposite direction after the shaft stops turning, you should use the voltmeter's first indication as to the status of rotation direction.

If you're lucky and the first connection configuration is correct, you label the motor's leads "A," "B," and "C" to coincide with the connected leads from the phase rotation meter.

Suppose you're unlucky and the voltmeter reads INCORRECT. Then you should swap any two of the MOTOR leads and hand-turn the motor shaft again. Now, the voltmeter should read CORRECT, and you should label the motor's leads "A," "B," and "C" to coincide with the connected leads from the phase rotation meter. You're not done yet, though, with the motor installation."...

http://www.ecmweb.com/content/determining-motor-rotation-direction

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#9
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Re: 3ph motor Direction of Rotation

09/04/2017 8:59 AM

GA for that!

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#18
In reply to #2

Re: 3ph motor Direction of Rotation

09/05/2017 7:31 PM

Thanks for your answer

Could you please tell me about abrand which you have worked with before ?

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#4

Re: 3ph Motor Direction of Rotation

09/03/2017 9:30 PM

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#8
In reply to #4

Re: 3ph Motor Direction of Rotation

09/03/2017 11:31 PM

Exactly! If it's not going the "right" way, just switch 2 of the leads around.

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#10
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Re: 3ph Motor Direction of Rotation

09/04/2017 9:04 AM

It's easy if you dare run it the wrong way to check, but there are situations where that would damage something, and it's a big job to dismantle kit to get a bare shaft. Presumably this is one of them.

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#11
In reply to #10

Re: 3ph Motor Direction of Rotation

09/04/2017 11:30 AM

<...it's a big job to dismantle kit to get a bare shaft. Presumably this is one of them...> Maybe, but this might be the only way to be absolutely certain that the motor is turning the correct way before it is connected to the equipment.

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#19
In reply to #4

Re: 3ph Motor Direction of Rotation

09/05/2017 7:32 PM

I mentioned that i wouldn't run the motor

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#20
In reply to #19

Re: 3ph Motor Direction of Rotation

09/05/2017 8:01 PM

See #2. Follow directions there.

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#5

Re: 3ph Motor Direction of Rotation

09/03/2017 9:37 PM

Doubtful you can. I have more than once replaced a motor of one brand with another one of a different brand and despite using s idientail wire to wire reconnect the second motor ran the opposite.

Most motors follow a fairly standard lead designation to rotation correlation but some do not.

Same with three phase transformers. Most match each other from brand to brand and model to model but not always.

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#7

Re: 3ph Motor Direction of Rotation

09/03/2017 10:03 PM

Buy a Phase Detector

Compare with data on motor.

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#12

Re: 3ph Motor Direction of Rotation

09/04/2017 11:40 AM

If all else fails, and apparently it has, a call to the manufacturer, the distributor or the person who sold you the motor to clear up this mystery in about one minute.

The forum can't see the motor, the motor nameplate nor the reason for your request.

Of course, if this is homework, or an interview question, the motor, the motor nameplate, the manufacturer, the distributor or the person who sold you the motor will not exist, thus making the question hypothetical and leaving you with a 50% chance of getting the question correct.

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#13
In reply to #12

Re: 3ph Motor Direction of Rotation

09/04/2017 11:50 AM

Er, though that is only half of it. The phase rotation of the incoming supply has to be compatible and correct too. According to legend, there is an area of the NW of England where the phase rotation is "the other way round" to the rest of the UK, nominally because of a historical cock-up in the connection of one of the high tension grid's branches; as a result the wobbles go backwards. Changing it so it is correct at that location would also involve simultaneously re-connecting every 3-phase motor downstream of that connection, which just isn't going to happen...

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#14
In reply to #13

Re: 3ph Motor Direction of Rotation

09/04/2017 3:04 PM

From #3, I got the impression that OP knows, " the sequence of the power supply".

A dangerous assumption, realizing as you quote, "The biggest problem in communication is the illusion that it has taken place".

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#17
In reply to #14

Re: 3ph Motor Direction of Rotation

09/05/2017 3:36 AM

Indeed, especially as the original poster used the word <...if...>!

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#21

Re: 3ph Motor Direction of Rotation

09/06/2017 8:57 AM

Since you know the direction of rotation as presently wired just exchange any two leads and the direction will reverse. No need to overthink it.

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#22

Re: 3ph Motor Direction of Rotation

09/10/2017 10:31 PM

Unless you are the mighty high intelligent guru. No body can tell the sequence without running the motor.

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#23

Re: 3ph Motor Direction of Rotation

09/11/2017 8:34 AM

I thought I made that clear. After I would finish winding a Stator and it had dipped and baked, I would test it. We used a two stage manual starter(Old version of a soft start). Someone would pull the lever down to stage one and I would take a large ballbearing and with a clockwise motion I would toss the steel ball into the Stator. If every thing is wired right, as I explained previously, and the ball would spin around the Stator, the motor would be assembled and shipped.

So to answer is , again, change A,B,C order, which you don't do, or you change the order of the motor leads that should be marked 1,2,3 corresponding to the A,B,C order of your incoming power, assuming it is wired to code. If yo have a 9 lead motor you still use leads 1,2,3.

If you can find a Motor winders hand book (or disc these days), it would be a handy reference to keep in your engineering library and good luck with your endeavors.

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#24

Re: 3ph Motor Direction of Rotation

09/11/2017 1:43 PM

Thanks for all your comments

the product which i'm searching for is fluke 9062

http://www.fluke.com/fluke/phen/electrical-testers/electrical-testers/fluke-9062.htm?pid=56153

and there is also Amprobe PRM-4

http://www.amprobe.com/amprobe/usen/electrical-testers/phase-sequence-testers/amp-prm-4.htm?pid=73491

According the manuals, these products indicates the motor terminals sequence to connect the motor at the right direction

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#25

Re: 3ph Motor Direction of Rotation

09/11/2017 3:05 PM

A two pole, 3600 RPM, 3Ph motor has 36 slots. There are 2 sets of 3 coils each consisting of 6 individual coils linked together. The beginning wire of the first set of coils is wire one or Phase One. You put then have the other two sets and the next one you put in the adjacent set of slots will be Phase Two and so on. That is why motors have numbered wires for the leads. That is all anybody needs unless the numbers are wore off. Then you would need a meter to tell you what wire is hooked to Ph1. One of the benefits is to reverse any two phases to reverse direction. Three Phase motors can operate from a reversing contactor, change the speed electronically with ramp up/ramp down and even apply dynamic braking.

If you don't know your supply is correct ,the meter or the numbers won't do any good because then you would have use a scope with three inputs or a power phase detector. The point is if you want to be 100% right before you turn it on, you will need two meters, because just knowing the motor wiring phase is just half of it. The other half is blind faith. That is a 50% chance of getting it right.

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