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Is there such thing as a 6 wire 3 phase motor with a starting cap?

hoohaa

Plastic
Joined
Nov 21, 2005
I finally pulled off the name plate of my Sebastian lathe motor. The plate reads:

Model: 8500 4082
PM 204 A.C 220/440
1 (HP?) 60
3.4/1.7 4 C.C.C.
1602331

I can't read the rest of the plate, including the wiring diagram, although I can see that it was once there.

This motor has a bracket spot welded to the case apparently from the factory. It has a large rectangular capacitor attached to the bracket, also apparently from the factory.

I am in way over my head at this point. I did quite a bit of google searching and came up short trying to figure out what I have.
 
I poured some water on the motor plate and the paint showed through. The pictures are huge (have to be in order to show the text) so I'm linking them:

http://i9.photobucket.com/albums/a97/brsmith/P1080061.jpg

http://i9.photobucket.com/albums/a97/brsmith/P1080062.jpg

http://i9.photobucket.com/albums/a97/brsmith/P1080044-1.jpg

I've got six unlabeled leads. Three appear to be yellow and three appear to be black or dark blue. How do I figure out which wire corresponds to which number? Ive identified three pairs using an ohmmeter. They all showed around 9 ohms of resistance IIRC.
 
The motor plate shows nine wires, are you sure there aren't three more tied together and stuffed down in there somewhere?
 
I've got six wires coming out of a hole in the motor's case. I have not seen any other wires hidden in there unfortunately.

Since I have six wires visible, wouldn't it seem likely that the motor was wired for 220v operation and the other three were tied together and tucked in at some point? In 440v operation it would make no sense to only have six wires accessible if I'm reading those diagrams correctly.
 
Ok, so you have six wires visible out of nine that are supposed to be there, and no start capacitor, right?

According to the motor plate that is a 3 phase motor with nine wires, and three of those wires are supposed to be tied together, leaving three pairs for L1, L2, and L3.

So there must be three more wires tied together in there somewhere.

Have you considered removing the motor from the lathe and taking it to a motor shop? I doubt they would charge you much just to check it out. And then, assuming it checks out, you are either going to need a rotary phase converter or a VFD to power it. I wouldn't use a static phase converter on a 1hp motor on a lathe, that would cut it down to a 2/3 hp motor.
My Sebastian 12x36 is running on a VFD at the moment, although I was powering it with a kickstart 5hp three phase motor as a cheap RPC for awhile. Kickstarting that 5hp got old real fast though.
 
I have a home built 5 hp RPC I'll be powering it with. And yes, it does have a starting capacitor. The capacitor appears to have been attached at the factory, which has me a bit confused.

And everything else you said was correct. The three wires that are supposed to be tied together are probably shoved back into the case.
 
re

well, 6 of them are the ends of the motor windings, so you could ohm those out and tell. I did this last year with a tumbler, it was wired either delta or wye depending on 220 or 440[worthlessly, i cannot remember which way is which ], but I didn't have no cap.........

i think it must be wye for the 440, l since that puts more resistance between the lines
 
Well I went ahead and pulled the motor out of the machine. There are two white wires, two yellow wires, and two blue wires. Each of the pairs of colors have a 9.8 ohms of resistance between them. I was not able to see any other wires tucked into the motor. It is possible that it was rewired at some point?

Here are the pics. I have a question: can I pull the rear case off of the motor without screwing up the rear bearing? I can't really see if there is another trio of wires hiding without removing it.

I cleaned up the wires and it turns out there are three pairs, one white, one yellow, and one blue (or is it black?). Here are pics of the cleaned up wiring:

P1080088.jpg


Here is an overall shot of the capacitor:

P1080086.jpg


Here is a closeup shot of the capacitor data plate:

P1080085.jpg


Here are two overall shots of the motor pulled from the machine:

P1080087.jpg


P1080067.jpg


Rear shot:

P1080081.jpg


This is all I see through the rear vent into the motor:

P1080080.jpg
 
capacitor

Is it possible that someone added the capacitor in an attempt to run it on single phase? I think I read 20mfd on the cap, that would soft start a 1 HP motor no load. I just did a 3/4 HP bench grinder for a guy and it starts nice on 15 mfd. If this is right you still need 9 leads from the motor, could be the other three are tied together inside the motor because they were too short to leave out. I would pull the end frame and scope it out. If you feel uncofortable doing that as Steell said a motor shop could sort it out and maybe relead and number the leads for you. If the motor is a standard nema unit with no special mount etc. a new motor mihgt be the answer too.
 
I pulled the rear of the case off. Here's what I see:

P1080093.jpg


There appear to be only six wires present. I went around with the ohmmeter to check for continuity and was able to identify a few of the windings in relation to the three pairs of wires. I have drawn yellow arrows where I found a winding that had continuity with the yellow pair and white or black for those windings corresponding to the respective color pair of wires.

windingid.jpg


I did not spend enough time to really track down every winding, this is just what I came up with initially. The ones you see marked were the easiest to access windings. Does this pattern tell you anything? I was expecting to see alternating white yellow black white yellow black all the way around but I don't think I have that here. I could pop off the front cover as well and that would probably help to really track down which winding is fed by which pair of leads.

P1080095.jpg


P1080097.jpg
 
6 lead ?

Judging from the bright colors of the sleeving inside,I would think this motor has been at least releaded. Very possibly rewound to a different configuration making the nameplate diagram obsolete. If you have continuity from white to white and nothing to the other 4 leads from white, and likewise yellow to yellow without continuity to white or blue etc. it would indicate 3 windings isolated from one another. Sure looks like a cofiguration as Gustafson spoke of ie. wye or delta. If connected delta for 240 the wye connection I believe would be 416, are you in one of the locations like UK or Australia where 240/415 is common, or did the motor come from an area with 240/415? If so it may have been configured so. If there is in fact 3 leads hiding that are connected together you would have 2 groups of three continuity wise as apposed to 3 groups of two.
 
Well i wired it up to 220 single phase as if it had the two run circuits and a starting circuit with the capacitor in series and it started right up and ran fine. I don't quite understand what has been done to this motor but it does start and run, so I'm putting it back in the lathe.

I do know I have learned a ton about three phase and about motors since I've been trying to figure this out. I love learning and this "problem" gave me a great opportunity to get my feet wet in a new area.
 
I'm going out on a limb here and declaring that this motor has no centrifugal
starting switch. It's my opinion that it started life as a dual voltage three phase
motor, and somebody doctored it up to start somehow with that capacitor.

Jim
 
That's precisely what I have found. And that is correct, there is no centrifugal starting switch. Will I need to somehow switch off the capacitor circuit either with a timer or a pushbutton? The way I just wired it just to see if it would turn over I had the starting circuit tied in full time with L1.
 
Yes, the cap must be taken out of circuit. The centrifugal switch is a common way, but a timed start, or a current-dependent relay for starting are also used, and can be obtained if desired.

The standard 2 voltage 1 phase motor would have 2 run and one start winding. The start in series with a cap would be connected across one of the other windings, never across full volts in high voltage mode.

The data plate shows an apparent 3 phase setup. But I assume you have not found the wires yet.

What you CAN do, is get a source of DC, preferably current limited (a resistor will work to limit current) or the 9.8 ohms may be good enough limiting......

Anyway, also get a cheap compass.

Energize one winding from the DC, with the rotor out. using the compass, find the N and S pole pair.

mark the N and S poles on the inside of the stator.

Move on to the next winding, and repeat.

When all 3 are marked, look at the result.

If it is now wound 3phase, the 3 N/S pairs will be evenly spaced 120 deg apart, with 6 poles, 3 N and 3 S.

if it is now wound for 1 phase, you will probably find that you have either 2 pole sets at right angles, or 2 co-incident pole sets. There will be another pole pair at an angle off from the others.
 
centrifugal switch

If the capacitor is a "run" capacitor it can stay in the circuit, If the run capacitor only doesn't give enough starting torque you will need some form of switch to take a start capacitor out. As I stated earlier I fixed a 3/4 HP Baldor 3 phase grinder up with a 15 mfd run cap and it does well, but a bench grinder starts almost no load. Furnace blower and AC condenser fan motors almost all are configured this way due to low stating torque requirements. As JST stated dc and a compass will tell you how the windings are distrbuted, a little tedious but tells the whole story like nothing else.
 
3 phase w/ cap Converter

hoohaa,

You have a very old conversion method with will give you about 90% of motor hp. It is similar to the H-A-S method. Below you will find a thread discussing the H-A-S method.

http://www.practicalmachinist.com/vb/showthread.php?t=102349

My comment in the above thread was:

About 15 or 20 years ago when I was doing research on static converters I came across a paper in an Industrial Electrical journal that showed a method of static conversion that claimed 90%+ hp just using a capacitor. The catch was that you had to have an unusual motor wiring leads setup so that the capacitor could be wired between the center of the star (star connected windings)and one of the coils. I assume that it would be possible to reconnect the motor windings internally to get the proper motor lead setup. I also remember some discussion about when rewinding a 3ph motor the internal star center connection could be brought out as motor leads for this type of phase conversion. I think I still have a copy of the paper. I'll see if I can find it.

I'm fairly certain this is what you have. I would require 6 leads (12 for a dual voltage motor)and a run cap to work. There is no starting circuit.

Joe
 
I finally pulled off the name plate of my Sebastian lathe motor. The plate reads:

Model: 8500 4082
PM 204 A.C 220/440
1 (HP?) 60
3.4/1.7 4 C.C.C.
1602331

I can't read the rest of the plate, including the wiring diagram, although I can see that it was once there.

This motor has a bracket spot welded to the case apparently from the factory. It has a large rectangular capacitor attached to the bracket, also apparently from the factory.

I am in way over my head at this point. I did quite a bit of google searching and came up short trying to figure out what I have.

Hi I have the same motor on my sebastian lathe.Its a Brown Brockmeyer Company B-Line M.S. 8500 E.S.4032 PM 204AC 220/440 Hp 1 Cyc 30 RPM 1150 or 1750 can't read plate. Amp 3.4/1.7 Temp 40.C.C Ser. Bo. 1643837 My motor is runing on single phase 110 volts. Maybe they converted the motors at the factory. I have to do more research Thanks Sid
 








 
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