How To Rewire Motor From 480V to 240V?

I labeled the wire pairs A, B and C then disconnected all of the wires and then ran a continuity check on the wires. I got a continuity beep when I connected the multimeter to one of my two "A" wires on my motor and the "1" wire on the motor and so I labeled that A wire as "A1"; one of my two B wires beeped on the 2 wire and so I labeled that B wire as "B2"; and as expected, one of my C wires beeped on the 3 and so I labeled that C wire as "C3". This gave me my original 1,2,3 wires, plus A, A1, B, B1, C, C1.

Does this mean the following:

4=A 5=B 6=C 7=A1 8=B2 9=C3

Or does it mean

4=A1 5=B2 6=C3 7=A 8=B 9=C

Thanks for the help.

FWIW, I had the exact same problem with my Mazak lathe. After getting all the help I could here, I still had four possible ways to try. I ended up hooking the motor up to a small motor contactor. The connection that didn't blow the overloads immediately turned out to be the one that worked.

Someone here may cringe, but the only other option was to take the motor out and bring it in to a motor shop.

karl

first, disconnect the power wires paired wires and keep them marked..

4,7 5,8 and 6.9 4 5 and 6 are the other ends of the 1,2 and 3 wires, so tie the wires together that have continuity to 1 2 and 3. and at the same time you can tell the 7 8 and 9 wires by the continuity checks from 1, 2 and 3. and that you know that 1 contunity to 4 which is tied to seven...... and so forth. 2 cont. to 5 which was tied to 8. ......... also 7, 8 and 9 wires other ends are tied together and buried in the motor so you will get contunity between 7,8 and 9.

Hope this helps......

John

I relabeled my wires (A,B,C,A1,B2,C3 became 4,5,6,7,8,9 respectively), and so here is where I have continuity beeps as it stands today:

4+5+6, 1+7, 2+8, and 3+9

Assuming this is correct then it seems that my next step is to do the following wire connections:

L1+1+7 L2+2+8 L3+3+9

4+5+6

In addition to the connections above, I also need to reconnect the 2 white wires from the motor that I labeled C2 and C3 because they were originally connected to wire 2 and 3 respectively.

Let me know if this sounds correct to the group. Thanks again for all of your help.

John, as I re-read your note, I think that I did it backwards to what you wrote. When I saw that I had continuity with what I had labeled as A, B & C I deduced that these must be 4, 5 & 6 since these 3 are tied together in the "low volt" diagram on the motor. But based on what you wrote, I should have relabeled my A1, B2 & C3 as 4, 5 & 6 because A1, B2 & C3 had continuity with 1, 2 & 3 respectively. and since you wrote "tie the wires together that have continuity to 1 2 and 3" it sounds like I need to swap my 4, 5 & 6 with 7, 8 & 9 respectively because I did it backwards to what you wrote here.

According to Mark Main :

O.K.

4 should have 1 as the other end and connect to 7 5 should have 2 as the other end and connect to 8 6 should have 3 as the other end and connect to 9 7, 8, and 9 join together inside the motor, after passing through three windings.

You will have to split the splice between the prospective 4&7 (it may be a 5&8 or a 6&9) check (with an ohmmeter) which one of the 1,

2, or 3 it is connected to, and label it according to the list above. Also label the one to which it was connected as 7, 8, or 9 as appropriate. Repeat until all are labeled. (Though you really don't need to measure the last one you open except for piece of mind.

Or -- if you would like to do it *without* labeling:

Open one splice. Check whether it is connected to 1, 2, or 3 through the motor winding (again with an ohmmeter). leave that one (4,

5, or 6) loose, and connect the other side of the just opened splice (7, 8, or 9), to the other end (1, 2, or 3) of the winding you just disconnected. Repeat with the other two splices. When you are done, you will have 1, 2, 3, and three loose wires, which are 4, 5, and 6. It does not really matter which is which in this case, because you are simply going to be joining them all together and insulating the joint anyway.

But just to be kind to the *next* person who has to deal with this motor, I would suggest that you use the first method -- and while you're about it, get some aluminum or copper 1/4" line, make a support arbor, and stamp the numbers 4, 5, 6, 7, 8 and 9 in them, and as you identify the wires, slip these over the wires and squash with pliers over the insulation a little back from the splice so they will stay and can be read years or even decades from now.

You *could* do the measurement without opening any of the splices, but you will need an ohmmeter which is very good with very low resistances, as these motor windings will not be far above zero.

The above are two ways you should be able to do it. I recommend the first, with the number-stamped collars. (Or -- you can go to a nearby electrical supply place (the ones which sell to electricians, not the local Home Depot), and get a little device which has ten rolls of white tape with black numbers stamped on it. This will be easier to do, but will probably cost you something like $18.00.

Enjoy, DoN.

According to Mark Main :

No! You should get a beep between A, B, and C, which will mean that they are 7, 8, and 9. The one which beeps connected to 1 will be 4 (A1), etc as below.

Yes -- this is the right way.

Let me draw it for you (using "W"s as windings. Be sure to use a fixed pitch font so this is not distorted by treating spaces as shorter than 'W's and '-'s.

(L1)-(1)---WWWWWWWW---(4)-(7)---WWWWWWWW---(X) | (L2)-(2)---WWWWWWWW---(5)-(8)---WWWWWWWW---(X) | (L3)-(3)---WWWWWWWW---(6)-(9)---WWWWWWWW---(X)

All three 'X's are connected together buried inside the motor, just as you will connect 4, 5, and 6 together in the wiring box.

When you are done, it will look like this (the "- | -" are where wires pass without connecting):

(L1)-(1)---WWWWWWWW---(4)--+

According to Mark Main :

I think that this is wrong, based on what you posted and I have already (just) answered. I think that your B1 should become 4, etc.

What do you mean here? You (with no splices at all in place) should get beeps between 1&4, 2&5, and 3&6, and beeps all ways between

7, 8, and 9.

Your meter can't measure ohms? It can only beep on low resistance?

I'm not at all sure about your C2 and C3. If they were connected between two of the heat coils on the contactor, I would think that it is an overtemperature switch to shut down the motor if it starts to overheat for whatever reason. I see no real purpose it to being connected to 2 and 3, however. Perhaps someone else knows what they really do. If you had an ohmmeter, I would suggest that you measure the resistance between your C2 and C3. As it is, check for a beep. If it beeps, I would first try running without them connected anywhere. (I guess that it might happen to be an emergency brake on the motor, in which case it will probably not be possible to turn the motor without power on it. And if so -- it *might* need rewiring at the brake assembly for the lower voltage -- or it might need a lower voltage brake coil.

Can you turn the shaft with no power applied? If so, then C2 & C3 are probably *not* a brake, and can be ignored. If not, then you might want to first try applying power only to C2 and C3 at 240V and see whether you hear a loud "CLACK". If so, you can probably connect them back with 2 and 3 and be alright.

Good Luck, DoN.

According to Mark Main :

This sounds right.

Good Luck, DoN.

the way it works is that the 7.8 and 9 wires are hooked up as a star config. In the low voltage mode you create two parallel stars. in the high voltage mode you add a series winding to each star, the winding being 1,4 2,5 3,6 . In the low voltage mode you tie

4,5, and 6 together to get two star configs.

John

i dont know what the white wires are for..... usually they are for a thermal overload indication, but not connected to the input voltage. There is normally only the nine wires needed to run the motor.

John

DoN & John, thanks for your help.

Based on what you've written I have swapped what I labeled as (4,5,6) with (7,8,9) respectively. With all 9 wires loose and not touching I rechecked my continuity tests and here is where I see continuity:

7+8+9, 1+4, 2+5, 3+6

This appears to be correct based on your coaching.

The motor shaft is on the right side as I'm looking at it and on the left of the motor is this attachment that is about 40% of the motor width and almost the same diameter. This appears to be where the white wires (that I marked C2 and C3) go.

I checked for continuity between C2 and C3 and the buzzing sound that I get when making a typically connection was faint (about 25% of the standard buzzing noise), but it did make a buzz. I'll try to get a picture of it uploaded and I'll hook just these two up to 240V to see if I hear a clank noise.

I connected the two white wires to 240V and it makes a clanking sound and then a hum. There are 3 round plates that move from the left toward the right about 1/8" (that's the clanking noise). The hum is fairly loud, but I left power connected for about 5 seconds and it didn't seem to be a problem. I used 22 gauge wire and that didn't get warm during that time either. Does it sound like a brake?

Being it is a lathe it is most likely a brake. You should be able to feel the drag with the power to the white wires on and off. Check for continuity between the two white wires and the rest of the wires in the motor. IT may be three phase and the third phase is tied together inside the motor.. unlikely ,, but check.

John

According to Mark Main :

[ ... ]

That sure sounds like an electrically operated brake, power to release the brake is typical.

O.K.

Good Luck, DoN.

According to Mark Main :

Yes it does.

Have you been able to compare how difficult it is to turn the motor shaft when it is powered vs when it is not?

Enjoy, DoN.

Sorry, about the delay. I'm working tons of overtime these days. I still have work to do tonight. I'll figure out the pictures this weekend. Thanks for the support.