Three phase motor connection.

[glenn1340]

I suppose most of us have been sometime over the years: a three phase motor returns from the rewinders and they`ve not marked up the new fly leads. Now, here`s my question: how do I find the correct location on the main/delta contactors for the leads. I know I need to find three pairs ie U1 U2, V1 V2 and W1 W2 but how do I proceed from here. Getting it wrong on a 2hp motor will probably blow a fuse, getting it wrong on a 150hp motor could be very expensive it not very dangerous.
I did have the procedure written down but that went when my van was nicked.
So if anyone can shed light on this black art can they share it with me please.

Thanks in advance guys.
Glenn

[Magoo]

Star connection:- power onto U1, V1, W1, Link U2,V2,W2.
Delta connection:- Link U1 & V2, V1 & W2, W1 & U2. power onto U1, V1, W1.

magoo

[Quality]

I would say left to right U V W or W V U if the leads are terminated to a terminal post

[chemi-cool]

it is not easy task to determine the sequence of the wires, its simple to find the pairs.

If you connect two pairs in one direction and one in the opposite, you will burn it in second.

I will ask tomorrow my compressor rebuilder how it should be done.

[Quality]

it is not possible to connect incorrect when you know the pair per winding . I don`t want to go down the BEAR route but 3 is the square of 9
123 - 132 - 321 -312
either way its the same 123

[GHAZ]

HI normally when you get a rewound motor you,ll have two colours and one set will eg say red and other set of leads will be black, the red set will be u, v, w and then just pair them using a multi meter with black leads and the pair of u will be u2, and so forth.

[frank]

http://t2.gstatic.com/images?q=tbn:ANd9GcSJ29rfnxbf6IjIVZQCZ42AyNhMw7P0S4Uw-OAW9ppJm84YBnF4

[chilliwilly]

I haven't got any drawing software so I can't upload any diagrams. But if you’re looking at the motor terminal box, there are usually six terminal posts. If you look at the posts and bell out the windings and make sure the leads correspond to their markings. From the top three posts, they should be U1, V1, W1, and from the bottom V2, W2, U2. If you then locate your main, star, and delta contactors, and bell out the leads from them down to the motor terminal box, and connect their corresponding posts matching the markings.

If you connect U1 to Red/brown, V1 to yellow/black, W1 to blue/grey, on the main contactor, then U2 to blue/grey,V2 to red/brown, W2 to yellow/black on the star or delta contactor, which ever one the tails are wired to as the terms will be commoned up. Then each of the windings will see 240 volt in star, then 415 in delta.

That way is always a safe bet, and the motor will start and continue to turn and won’t try to stop or reverse and blow the fuses when it switches to delta. As for the direction that’s another story, there is a phase rotation meter that will tell the direction according to the phase sequence. Some of the more expensive meters have that function on them.

[Magoo]

If motor re-winder does not identify coil tails, he should receive a short sharp kick to the groin, then send re-wind back to them. They stick a low voltage current through each coil set and with a whirly gig get a rotation, so can identify U1 versus U2, and the rest of the coils

[Peter_1]

I think some posters don't understand the question. The original poster knows how to connect. measuring the coils is easy with an ohmmeter. Problem then begins you have to know from each coil which wire gives you have to connect together from all coils to be sure that all windings generate a rotating field and not 2 windings CCW and 1 CW.
I've heard once that you have to connect a DC voltage (battery 12VDC) and apply a voltage to one coil. You then have to release the voltage while measuring on another winding. The counter EMK will say you how the other coils is connected. Repeat this 3 times. Never tried it myself.

But as Magoo said: a bad rewinder you have, he should give you the proper connections.

[chemi-cool]

I had a long talk about that problem with my compressor re builder.

Assuming you get a motor that was rewind and the phases are not marked, you can find the three pairs but there is no way you can guess the sequence, if you try and get one of them wrong, you burn the motor immediately.

I'd go with Magoo and add, if that the kind of job you get from your motor re winder, find another one.

[taz24]

http://t2.gstatic.com/images?q=tbn:ANd9GcSJ29rfnxbf6IjIVZQCZ42AyNhMw7P0S4Uw-OAW9ppJm84YBnF4

You been doodling again Frank. :)

taz

.

[frank]

A picture is worth a thousand words....;)

Thought it might help those that dont understand star delta wiring

[glenn1340]

Thanks very much guys. Lots of usefull information for me to print out and digest while I`m sitting in my van waiting for islolations to be taken off.

Regards,
Glenn

[chilliwilly]

I think some posters don't understand the question. The original poster knows how to connect. measuring the coils is easy with an ohmmeter. Problem then begins you have to know from each coil which wire gives you have to connect together from all coils to be sure that all windings generate a rotating field and not 2 windings CCW and 1 CW.
I've heard once that you have to connect a DC voltage (battery 12VDC) and apply a voltage to one coil. You then have to release the voltage while measuring on another winding. The counter EMK will say you how the other coils is connected. Repeat this 3 times. Never tried it myself.




But as Magoo said: a bad rewinder you have, he should give you the proper connections.


Yes rewinders should do their job properly, they charge enough for it. There shouldn't be a problem though once you've identified the windings and apply phases directly to one side of them. i.e. tail ends uvw 1 thus, red/br u1, yel/bla, v1 and blu/gre w1. And tail ends uvw 2 to the star contactor. Then blu v2, red w2, and yel u2 to the delta contactor. (RYB- BRY) The opposite tail ends can be connected vice versa. The phase sequence will then follow red, yellow, blue, so that each winding will synchronise with the supply, and that way all the windings will follow the same rotational orientation.

If you were wiring directly on line, you would simply use the strappers inside the terminal posts, and apply phases to both sides of the windings using the same configuration as the star and delta contactors.

I've never heard of connecting a battery to one of the coils or windings, whilst applying voltage to one of the other windings. The battery would more than likely explode due to the current flowing through the configured connection of the winding that's online. You wouldn't be able to repeat it a second time, let alone a third.

I've connected live wander leads to contactor coils and the like, to speed up fault finding. But with the fuses removed or overloads tripped to disable any final outputs. But that doesn't solve a star or delta configuration or direction of a motor.

There was a very old method used years ago, that would definitely still work today. And that’s using two light bulbs and a capacitor. But its been that long I’ve forgotten how to do it.

[big bear]

hi mate when you say ' rewound 'by the people who have re-vamped your motor have they left the connector plates attached to your motor i.e straps who sent it away ? they usually strap the plates how it should be Probbably delta connection this one use to baffle me but have spent lots of time studying it aswell as my job today funny enough still used this One thing to remember is you always look up to the stars so 'Star' configuration can be high Voltages Please send a picture if you can i Might be able to help you. Is your contactor i e connections star delta or straight of one contactor ???? let me Know :-)

[ktmtragic]

The simplest method is :
Assuming you know the end groupings

Using a multimeter ring out the six leads on the Ohms scale (ie you will end up with 3 leads in each hand) Then call the leads in your left hand A1 B1 C1 and the other ends for each winding in your right hand A2 B2 C2.
I remember this part buy calling a CAB.

Connect A1 to C2, B1 to A2, C1 to B2,
Or
A1 B1 c1

to


C2 A2 B2


Six black leads "OUCH" bit harder

Ring out one winding.
Attach a 9V battery to the ends. NOTE the polarity of the battery. Using an analog meter ring out the other 2 windings, the meter deflection should be positive if not switch meter leads over. Now lable the 2 leads you have rung out with the red or positive meter lead A1 and B1. Now connect the battery to the A1 and negative to A2 Then put your meter across the winding the battery WAS connected to and check for positive deflection of the meter. Then all you do is switch ends on the last winding so the wire that was connected to the the negative of the battery is now C1
So now we know which group is the begining and end of each winding withouth running the risk of getting the ends mixed up.
Then connect as in the first method.

I hope this is clear enough
Cheers

[wambat]

Try this: http://www.joliettech.com/3ph_motors_single_speed.htm

[chilliwilly]

Nice link, I used have all those configurations in a book that was given to me from a retired lift/elevator engineer, But I can't find it any where.

[Peter_1]

I've not said connecting a battery on one winding whilst another is energized with another voltage: I said applying a DC voltage of a small battery - which will not explode - and measuring the counter EMF (is an auto generated field) on the other windings when releasing the voltage on the 1st winding.http://www.tpub.com/neets/book2/5e.htm and http://www.youtube.com/watch?v=6Aad2p-XO28

[wambat]

Nice link, I used have all those configurations in a book that was given to me from a retired lift/elevator engineer, But I can't find it any where.

Have you noticed all of the other information ? it's quite comprehensive!

[chilliwilly]

I've not said connecting a battery on one winding whilst another is energized with another voltage: I said applying a DC voltage of a small battery - which will not explode - and measuring the counter EMF (is an auto generated field) on the other windings when releasing the voltage on the 1st winding.http://www.tpub.com/neets/book2/5e.htm and http://www.youtube.com/watch?v=6Aad2p-XO28

Sorry Peter its how you typed your post, I wasn't trying to make a twat out of you. You typed connect a DC battery and apply a voltage to one coil/winding. I assume you mean you set up a back emf from when disconnecting the battery from one of the coils and then induce a voltage to the other two coils/windings. And in turn measure the polarity of the voltage with a centre zero moving coil/analogue meter.

I will give that a try the next time I get a chance to have a play. As it does sound an interesting method of testing for directional vectors within a motor. But in the meantime I think I'll stick to the tried and tested RYB-BRY or L1, L2, L3,- L3, L1, L2.

[chilliwilly]

Sorry duplicated post.

[chilliwilly]

Have you noticed all of the other information ? it's quite comprehensive!

Indeed it is, I managed to dig out some old diaries from the nineties from Dowding and Mills, and Berl. They've got similar information in there. Unfortunately the multi speed motors are becoming a thing of the past, due to silicone technology. But they're still around, especially on cranes and other transmission applications and also the larger industrial fans. I just wish I could find the book that I was given, It had a brilliant section on Ward Leonard systems.