Surface Grinder Electrical Problems (RESOLVED)

Charles Vestal said:
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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I understand that there is a possibility that the motor may be wired wrong, but as mentioned previously, the motor is too close the wall to really get a good look at the inside of the motor, much less get a screw driver back there to remove the cover. Moving the grinder isn't an option either because I lack the equipment to safely move it away from the wall and return it to its original location. So checking out the motor is going to be the last thing I do. I want to sort out all other possibilities before completely dismantling the upper assembly.

Salem: I'm going to check the voltages in a few hours when I get home from school. I'll post what I find then. Maybe I'll start saving up for a VFD, that would be a good addition to the shop regardless of whether or not I use it on the surface grinder. You can never have enough tools :D
 
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Charles Vestal said:
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
Click to expand...

Don't do this yet.
 
xXBackyardCrafterXx said:
I understand that there is a possibility that the motor may be wired wrong, but as mentioned previously, the motor is too close the wall to really get a good look at the inside of the motor, much less get a screw driver back there to remove the cover. Moving the grinder isn't an option either because I lack the equipment to safely move it away from the wall and return it to its original location. So checking out the motor is going to be the last thing I do. I want to sort out all other possibilities before completely dismantling the upper assembly.

Salem: I'm going to check the voltages in a few hours when I get home from school. I'll post what I find then. Maybe I'll start saving up for a VFD, that would be a good addition to the shop regardless of whether or not I use it on the surface grinder. You can never have enough tools :D
Click to expand...

Look in to salvaging a treadmill motor. You'll get all the controls, around a 2HP motor, and speed control. Might can get one free but def very cheap.
 
Alright, I checked the voltages again, this time with the T legs disconnected. All Leg to ground voltages read 120 volts. From T1-T2, I got 440 volts again. From T2-T3 and T3-T1 I got 220 volts. I also realized that the settings on the converter were for high HP motors, so I switched around the two wires it says to for the low HP motor setting. I got the same voltages. Could this be a matter of amperage and I just had the converter on the wrong setting or is there genuinely something wrong here?
 
Not a matter of amperage, that is a separate matter from the voltage. I think your converter is screwy.
What do you get when testing each leg to ground? At any rate, the values are too high. You should get 120 each or so, with any of them 240-ish in a pair if you're getting good three phase out of that box. Or, as Nathan says, high-leg delta would be two legs of 120-ish and one leg at 190-208-ish, but I don't imagine the static converter would be putting that out.
Is that a direct drive, or belt drive motor? I ask because a treadmill motor won't be such a good option for direct drive.
Sorry, I don't recall, have you tried calling the converter manufacturer and talking to the techs there?
 
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I'm fairly certain it's a direct drive. Each leg when tested to ground gets 120 volts.
 
OK, so with the hot wires from the converter completely disconnected, i.e. wire nuts on the ends that you can push you test probe into, do those voltage readings you got remain the same? If so, and I imagine they will be, the converter is faulty or needs some internal wiring done/fixed. It certainly appears only to be designed for a 208-240V output.
 
Yes, they stay fairly consistent. I'll call customer service and see if It's anything I can fix or if I can get a replacement.

ETA- I called customer service and they said that having the switch between the motor and the outlet is the problem. The representative I spoke to said to wire the motor directly to the phase converter. Does this sound right? I'm not quite sure how I feel about having the spindle start up as soon as I plug it into the wall :(
 
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I don't know about that. I have a switch before my phase converter and one on the machine after and it runs just fine. I am curious where did you get this converter? I've never seen one like this, it seems pretty bare bones. My phase o matic has decals and branding on it. I'm starting to think the same as Salem that there is something off or fried in your converter.

On a side note I would not consider a tread mill motor for a surface grinder. I've read you don't even want to replace those motors at all because they are precision balanced for a surface grinder, to reduce chatter I'm assuming. I believe I read that on PM as well as here and I think it was Nathan that pointed it out. That probably isn't as imporatant if its belt driven.

Also I read what Salem said about the solid state converters introducing chatter, but I have had pretty good luck with mine. A real machinist probably would not be too impressed with the finish mine is capable of. For me though, it does get the job done and not all of us are fortunate enough to have a nice phase perfect ;)

-Clint
 
I got mine on eBay from TEMCo directly from the company. It had good reviews when I checked.
 
I'm still a little confused about how your SPC puts out 440 with nothing connected, but again, I don't really have experience with SPCs. Wiring directly to the motor shouldn't be huge problem for that size motor. You would simply wire a DPST before the SPC on the lines feeding the 220 to the SPC. Just make sure it's rated for the amperage the motor will draw.
 
What do you mean by DPST? I think I understand what you're saying though. I could wire up the switch between the wall and the converter and put the converter between the switch and the motor...Would my 3 phase switch work for that if I just used two of the legs?
 
Double Pole Single Throw. It will ensure that both hot legs of the 220VAC feeding your converter will be disconnected.

As for using the 3 phase switch, I don't know that the contacts would stay closed with an open leg.
 
Where is 440v coming from? That makes no sense to me. I don't know how a convertor like that is wired inside but it sounds like legs are bleeding into each other.
 
knife to a gunfight said:
Double Pole Single Throw. It will ensure that both hot legs of the 220VAC feeding your converter will be disconnected.

As for using the 3 phase switch, I don't know that the contacts would stay closed with an open leg.
Click to expand...

What would make it not stay closed?

kuraki said:
Where is 440v coming from? That makes no sense to me. I don't know how a convertor like that is wired inside but it sounds like legs are bleeding into each other.
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I have no idea, but the representative I spoke to earlier didn't seem alarmed by the 440V and he didn't think it was out of the ordinary. I don't know if I should trust him or not...
 
If I'm not mistaken, most motor contactor switches now days have a built in phase protection that opens the contacts if a phase drops out. Whether yours does, I can't say, other than to try it and see.


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Okay, I'll try setting it up like that tomorrow and see what happens.
 
That switch does not have a magnetic coil. It has a manual on/off. Your plug can be wired to two legs, then fed from the load side to the converter but this won't solve your problem. It sounds like there's some sort of jumper settings on the converter? Either way, tech support should have been able to tell you what's up. Any switch before or after won't cause what's going on especially since it was completely disconnected when the volt check was done.
 
Oh...I see...
I guess they're saying the readings are fine, but the heaters are burning up because the switch should be before the converter. Sounds legit since it seems to run ok until the heaters act up.
so, yeah...wire the plug to the switch, then to the converter, then the motor.
You can still use the existing 3 pole switch.
The work around for the two pole circuit on a 3 pole contactor is to take the load from the first pole and jumper it to the second pole line side. I don't think you'll need that though. Just use whatever two poles.
 
Alright, I'll do that then and see what happens! I'll update this when I make the changes.
 
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