Surface Grinder Electrical Problems (RESOLVED)

I'm with #s ^. I think your wiring inside the motor isn't configured properly. It could have windings connected wrong, but I expect it's simply set up for the wrong voltage.

This sounds complicated, but it's really really simple. The wires under the motor plate will either be numbered or colored. There will be a simple diagram that shows which wires to connect to each other (it's different if you're running the motor under high voltage or low voltage, 220-240 or 440-480), and where to connect your three legs of incoming power. It doesn't matter which leg you attach to the different line inputs in the motor, but if the motor is turning the wrong direction you swap any two incoming legs.

I've never seen a static phase converter, solid state converter or RPC fail to work. It's all really very simple. Getting a motor to turn is easy, that's all it wants to do.

The voltages you measure from your phase converter can be different things. What really matters in this application is leg to leg, which should be around 220V. (208 up to 250 is probably okay, your phase converter probably has little or no control over that and it's a matter of your own incoming power)

If you're generating 3 phase, you'll have two legs that are 110 to ground and 220 to each other, and your generated leg that's about 190 volts to ground and 220 to the other legs. If you have true (modern) three phase your legs will be 120 to ground and 208 to each other. This is because single phase power is 180 degrees opposed where three phase is three legs that are 120 degrees opposed. <--- that's not important for you to understand, but just in case you're curious. The significance is that it's normal for the wild leg to measure high when compared to ground. That's because it only has 90 degrees to play with. For the motor, it's leg to leg voltage that counts.



edit to add: I'm not an electrician nor an electrical engineer, I'm just a dumb machinist
 
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I'm going to check the voltages tonight. If nothing useful can be deduced from those readings, I suppose I'll have to dismantle the upper assembly and take a look at the motor. Updates soon to follow.
 
Okay, I just checked the voltage. When I put the leads of the meter on the Left and the central legs, I got 91v and when I put it on the Right and center legs, I got 312 volts. I'm no expert but that doesn't sound right.

ETA- Here's a picture of the data plate.
 
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Yeah, something is wonky.
Let's use from left to right A B C
Check each single leg to ground, then leg to leg:
A to B
B to C
A to C
Also note which leg is the generated leg.
Ideally, this should be done at the T1 T2 T3 terminal in the converter AFTER disconnecting the output leads.
Basically, you want the incoming power on and connected but remove the output wiring to eliminate any possible factors that could affect the true reading of what's coming out of the converter.
Also check each incoming leg to ground and leg to leg.

Incoming should be 120ish to ground and 240ish leg to leg.

Then Report back. I'll be hanging out checking back here for a while.
 
If the shop it came from was running a lot of large machines on 3 phase power, I can almost guarantee it was wired for 480. If the leads are numbered, you'll have 1, 2, and 3 to line voltage, and then 3 pairs twisted together (or possibly tied together on a bus bar) as follows: 4&7, 5&8, 6&9.

You're gonna want it wired for 220, which, IIRC, is 1&7 (and first line), 2&8 (and second line), and 3&9 (and third line), with 4,5,6 tied together. I believe that's for wye configuration, low voltage. Delta is slightly different, but for your purposes, wye should suffice.
 
NCSlice said:
Yeah, something is wonky.
Let's use from left to right A B C
Check each single leg to ground, then leg to leg:
A to B
B to C
A to C
Also note which leg is the generated leg.
Ideally, this should be done at the T1 T2 T3 terminal in the converter AFTER disconnecting the output leads.
Basically, you want the incoming power on and connected but remove the output wiring to eliminate any possible factors that could affect the true reading of what's coming out of the converter.
Also check each incoming leg to ground and leg to leg.

Incoming should be 120ish to ground and 240ish leg to leg.

Then Report back. I'll be hanging out checking back here for a while.
Click to expand...

Alright, I found some very interesting values.
Output-
A-B:440 volts
B-C:250 volts
A-C:250 volts
A-Ground:120 volts
B-ground:120 volts
C-ground:120 volts

Input-
A-B:440 volts
B-C:250 volts
A-C:250 volts
A-Ground:120 volts
B-Ground:120 volts
C-Ground:120 volts
I also noticed the thermal overload relay that has been giving me trouble and burning up was cold-absolutely fine (and I had it turned on for much longer than it takes to blow it with the motor plugged in)

knife to a gunfight said:
Can you take a pic of the wires inside the motor pecker head?
Click to expand...

At this point, taking the motor apart is a last ditch sort of thing because the only way to access the internals is to either move the grinder using tools I don't have or remove the entire upper assembly of the grinder. The motor is too close to the wall for me to get a screw driver in there or even get a good look at the inside even if I could open it. It's looking like I may have to resort to this though :(
 
Are these voltages with the motor running? Or just with the SPC turned on and the motor disconnected?
 
I disconnected the motor for these readings. Sorry, I should have mentioned that. I suspect that's why the relay didn't heat up.
 
I'm not understanding where the 440 is coming from. You're supplying only 220VAC to the SPC correct? What kind of meter are you taking readings with? Is there a transformer somewhere in the mix that's stepping up the voltage? I must admit, I'm a little better versed on VFDs and actual 3 phase equipment, and haven't worked much with static converters. That said, I don't think you should be seeing 440 anywhere.

As for moving the machine, I can normally scoot mine around with a 4ft pry bar pretty easily. You may only be able to pivot it about an inch at a time, but it's better than nothing. Two bars are even better. ;)

EDIT: Your meter isn't reading peak to peak voltage is it?
 
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You are correct, I have 220V AC coming into the static phase converter. I'm using a "Split Jaw Smart Meter". I used the leads coming off of it to measure the voltage, not the Jaw at the front. I know the transformer takes in the 220V and steps it down to 110 for the outlet right next to it, but couldn't say for sure if that would have anything to do with the problem. I think I'm going to have to check out the motor tomorrow. As for moving the grinder, I have tried moving it with a 4 or 5 foot long 2x4, but I didn't get anywhere. Even if I did manage to get it away from the wall, I would have to get it back against the wall because my shop is a 2-car garage and I need all the space I can get :eek:

ETA: The purple wires got to the transformer. They are connected wires-black and white- with wire nuts to the left.
 
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xXBackyardCrafterXx said:
You are correct, I have 220V AC coming into the static phase converter. I'm using a "Split Jaw Smart Meter". I used the leads coming off of it to measure the voltage, not the Jaw at the front. I know the transformer takes in the 220V and steps it down to 110 for the outlet right next to it, but couldn't say for sure if that would have anything to do with the problem. I think I'm going to have to check out the motor tomorrow. As for moving the grinder, I have tried moving it with a 4 or 5 foot long 2x4, but I didn't get anywhere. Even if I did manage to get it away from the wall, I would have to get it back against the wall because my shop is a 2-car garage and I need all the space I can get :eek:

ETA: The purple wires got to the transformer. They are connected wires-black and white- with wire nuts to the left.
Click to expand...

Just for grins and giggles, I might try disconnecting the purple leads and see what happens to your voltage readings and THEN see if the motor runs, although I'd still wager it's wired for 440, it may not be.
 
That's a good idea, I'll try that tomorrow. I should probably start my homework about now :rolleyes:
 
I'm sorry.. I fell asleep lol.

Did you take these readings at the converter connections or the contactor switch?
I guess I wasn't clear enough
Everything should be disconnected from the converter in order to isolate any issue that might be down line.
Need to start at the top.
At the phase converter:
L1 L2- should be connected and powered up
T1 T2 T3 -nothing connected
Check Ts to ground then phase to phase
Also check also to ground and phase to phase.
 
Ah, okay, I see what you mean. I Checked it from the switch, not the converter. I'll check that as soon as I get home. Thank you for correcting me :thumbup:
 
At least you varified that the voltage is passing through the switch ok.
If the readings at the converter are funky then you may not have to mess with the machine at all.
Also want to varify that the incoming voltage is correct. If it's determined the converter is the issue you can call tech support and they might can help troubleshoot or determine if you need a replacement unit.
If it is ok at the converter, you can try completely disconnecting that 110v transformer then check your voltage
 
Alright, I'll update this when I check the converter tonight. Thank you guys so much for your help!
 
It sounds to me as if it is your converter. With the motor, start switch, transformer etc. disconnected, the voltage readings from leg to leg and from leg to ground are wildly wrong.
You want to make sure you're checking the voltages in the lines coming in from the static phase converter, right at the terminals, with no circuitry of the machine hooked to them.
I have an old phase-o-matic that I got with a milling machine, never have used it as there are better options now that are quite affordable. Ideally I believe you'll want smoother power than that thing can produce, for finishes on that grinder. It's too bad you don't have a VFD there to test it with...
 
Several people have told you to check the wiring IN the motor. If the motor is wired for high voltage you will not be able to run it with your setup.

Verify and rewire the MOTOR if necessary. Do not worry about your Phase Converter until you check the motor internal wiring. I might have missed that you have already checked this, if so sorry for

the reply.

Charles
 
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