Electricians I need a little advise

[Chris Byrne]

Hello all. I was working at the lathe tonight machining some metal and the lathe motor suddenly sounded like I threw it into reverse. I immediately shut it off and I could hear a hum/buzz like the motor was getting power but not spinning. The switch was in the off position while I was hearing this. I hit the safety stop button and let it sit for a while to cool off. I was not doing any heavy work or anything but the motor did feel a little warmer than I remember it should. After about 30 minutes I plugged it back in and reset the safety button and am hearing the same buzz. I assume this is a relay contact sticking and sending power to one phase of the motor.
I turned on the switch and the lathe started to spin up but slower than normal. I decided to shut it off as something is definately wrong but before I could get my hand to the switch there was a small explosion in/around the motor and a puff of black smoke. I slapped the kill button and unplugged the lathe.
For around the last month every once in a while I would hit the on switch and the lathe would either not spin or would take a half a second and then start spinning. When it would not start I would here a buzz but louder than it was tonight with the switch off. If I grabbed the chuck and moved it at all it would spin right up to speed like normal. It only happened a couple times but it never did this before. I have another identical lathe on the same breaker and it always starts correctly so I believe the power in is not the issue.
The lathe has a 220V single phase 1.5hp motor. I have the manual and will try to get the schematic scanned so I can post it. it shows 3 AC relay contactors, a transformer, heating relay, 2 fuses, the selector switch, and the safety switch and inching switch and power bulb and the motor.
I believe I fried the motor or possibly a capacitor and, also have an issue where power is being fed to the motor even when the selector switch is off. I am not sure what is up with the occasional no spin when the switch was on. The motor would hum so I was thinking one of the legs of power was not getting to the windings but that is just a guess.
So, anyone who knows 220 motors I would appreciate any info you could share.Thanks Chris 720 206 4034

 

[Jim Baxter]

Not a good sighn !!

 

[dchristal]

I'd be replacing capacitors (especially the run capacitor) first. They are inexpensive, more likely to go, and a little difficult to diagnose. Then, if the problem persists, I'd look into relay and switch problems. I'd suspect the motor last.

Disclaimer: I'm wrong a lot.

 

[Mc2]

Chris, if you can spin the motor and it takes off that would be an indication you are missing a phase. Lets hope it is a contactor. Usally a contactor will switch both phases into the motor. It is possible that you welded one side shut. That would be why it hummed when switch was off. Now it is possible that the side that welded shut may have over heated and then blew apart. I would make sure that I was getting both 220 phases to the motor when switched on. If you are confortable with this then get someone who is. It is possible that the starter cap is bad. I would check and make sure that both phases are presant at the motor first. If voltage is presant then try replacing the cap. Is this a Grizzley? Then are actually good to work with over the phone and do keep the parts on hand. When you find the bad part it will be odvious. I put my money on the contactor which can be well under $100. Oh by the way, the motor will start up slow if it is cold like it has been here in Good old Fort Wayne.

Jim.

 

[olsonsview]

Are you near a motor rebuilder?

You can first use your nose and smell the motor for signs of ozone/burning. If it reeks, then pull it out and take it to a good rebuilder for an estimate. He will test it in a few min and tell you where you stand, and if it is feasable to even rebuild. Many motors nowadays are throw away. You can try to bypass all your relays and hook up the power directly to the motor first ,but if it stinks in the motor housing and not the relay box, just pull the motor and get a pros opinion.
If you do want to replace the cap, then either give it plenty of time off the power source to bleed down, or discharge it with a high wattage resistor before touching the terminals. You may get your hair restyled if you get careless there. You can test it with a voltmeter to make sure it is bled down.
If you buy a new motor, make sure that the hookup is identical, if not, show the supplier the schematic and ask for advice on how to wire it when you reinstall. Best wishes.

 

[Chris Byrne]

Thanks guys. I have an idea but I just know enough to be dangerous. I will give it a look tonight. I suspect I will start by removing the wires from the motor and testing for voltage with the switch off and in the on position. I know something it stuck on somewhere. Chris.

 

[Mc2]

Thanks guys. I have an idea but I just know enough to be dangerous. I will give it a look tonight. I suspect I will start by removing the wires from the motor and testing for voltage with the switch off and in the on position. I know something it stuck on somewhere. Chris.

Chris, every thing described points to a welded contactor. With power off and un plugged do a contanuity test from both sides of the contactor vertically. They should show open. If one is shorted than it is welded together. Then if both show open push in the plunger manually. Then they should show shorted top to bottom. If they don't both show shorted it may be bad however then you will need to fire the contactor via the on switch with power and measure. You will want to measure from each motor lead to ground and have meter set to AC. Be careful. You should measure 200 to 240v. If one measure alot less than it is open. I doubt the motor is toast. I don't care for motor rebuilders as they tend to do repairs weather needed or not. But if it is bad it may smell.

Good luck.
Jim.

 

[Chris Byrne]

Thanks Jim. I will do that and see what I can find. I also need to find what snapped and puffed the smoke. I assume I will find that visually.

 

[dchristal]

Thanks Jim. I will do that and see what I can find. I also need to find what snapped and puffed the smoke. I assume I will find that visually.

Still bettin' on the cap.

 

[Chris Byrne]

I don't doubt they are bad with all the starts thay have done over the last 10 years that I have been using this machine.

 

[RocketQ]

Chris give me a call.
724-331-6649 East Coast Time have league tonight but should hear the phone.

 

[poolplayer2093]

it sounds like something is making the motor stick. you should get a multi-meter and see if the motor is still receiving voltage when you hear the humming. there should be a sticker on the motor saying what voltage you should be looking for. if the multi-meter reads anything but zero than you might have a relay problem

i think that's how that should work anyway

if you post a schematic i'll show it to a buddy of mine and ask him what he thinks

 

[Jack Flanagan]

beware of free advice, Chris.

sent you a pm.

did you ask this in the ICA forum ?

.
.

j.....(jack of all trades, master of a few)

 

[Tooljunkie]

Chris, I had the same problem a couple of years ago with my lathe, it wound up being the start capacitor. I replaced both the start and run caps and have not had a problem since. good luck, Jim

 

[Mcues]

Chris,

A few months ago my lathe was having a similar problem where when you turn it on it would not spin but if you move the chuck it would come up to speed. I clean the relay contactors and it solved the problem. Of course, your problem sounds like some damage was done to the capacitor or relays.


Mario

 

[Chris Byrne]

Ok. First off the manual was wrong. The motor plate says 2hp. single phase, double capacitation, induction motor.
I removed the motor and did find an exploded capacitor. it is the small 150uf capacitor and it for sure let the magic smoke out. It has the 2 wires attached to it with crimp on eyelets but there appear to be no screws. It looks like 2 dabs of solider or whatever was there melted. Everything is black from the explosion so I cannot see if the insulation for the 2 wires is melted or not. I did not try to ohm them yet as I don't know how the 2 wires should test.
Before I removed the motor I pulled the wires to it and did some testing. I found the relays open and close (viewed by the "indicator tab" that protrudes thru them) when the lathe is powered on and off and forward and reverse. I have 5 wires total from the controll box. there is a case ground and 4 others that attach to the motor.
Z2- black wire
Z1- blue wire
U1- brown wire
V2- white wire
When I power up the lathe with the motor wiring removed I still hear a little hum I have not heard before this happened. I do not see the plunger moving on the relay that closes when I power it up. I tried pushing the plunger to see if it was vibrating at all and no change. I do not know yet where the buz is from.

With the lathe powered up but not in a run position they measure
Z2- black wire 16.8v
Z1- blue wire 121.1v
U1- brown wire 7.6v
V2- white wire 15.3
I think the blue wire should not be powered unless it is to charge up the capacitors for starting. and I don't know about the low voltages on the other wires. I used a fluke 88 meter for the tests so I don't think they are "false zero" readings I might get with a cheap meter.
In forward they measure
Z2- black wire 1.3v
Z1- blue wire 120v
U1- brown wire 120v
V2- white wire 120v

In reverse
Z2- black wire 25.2v
Z1- blue wire 120v
U1- brown wire 120v
V2- white wire 120v

 

[Chris Byrne]

Ok I got them scanned.

 

[rhncue]

Ok I got them scanned.

If you will look near the end of the armature shaft there will be a set of points that are centrifugally operated. These allow voltage to the starting capacitor and once the motor is up to speed they open cutting off the voltage to the capacitor. This relay usually either sticks or burns through causing voltage to continue to the starting capacitor overloading it. Take a look.

Dick

 

[dchristal]

If you will look near the end of the armature shaft there will be a set of points that are centrifugally operated. These allow voltage to the starting capacitor and once the motor is up to speed they open cutting off the voltage to the capacitor. This relay usually either sticks or burns through causing voltage to continue to the starting capacitor overloading it. Take a look.

Dick

Ok, now that's good advice.

 

[Chris Byrne]

If you will look near the end of the armature shaft there will be a set of points that are centrifugally operated. These allow voltage to the starting capacitor and once the motor is up to speed they open cutting off the voltage to the capacitor. This relay usually either sticks or burns through causing voltage to continue to the starting capacitor overloading it. Take a look.

Dick

Do you know if the power on the blue wire with the motor is off is normal? Is it there to charge up the capacitor? Thanks Chris.