Electric Motor Shuts Down

[ALinCarolina]

I have a 20" Grizzly disc sander that has gone on the blink. It has a 2 hp induction motor with built in brake. It is a few months over a year old so out of warranty. It will start to run but a few seconds afterward it shuts down. I hear a click in the switch when it does. The points are not opening before it shuts down and if I try it a few times in a row it seems to shut down quicker, I assume from heat.

I hope some of the experts on here can tell me if it is something easy like replacing a run capacitor or adjusting the points or whether I need a new motor. That would be a shame as it has extremely low hours on it so far. Any tests you can recommend? Here is a link to a short video:

https://drive.google.com/file/d/1O2VQFAjlrRfc6XaExlhCsc_atv4KfgDM/view?usp=sharing

Here is a photo of the magnetic switch

 

[DanEng]

Check if the motor can turn freely with your hand, obviously disconnect from electrical supply first. The motor could be braked somehow, which will draw more current, heating up and make the thermal overload protection trip. The overload is the device fixed underneath the contactor shown in the photo.

 

[ALinCarolina]

Well it has a built in brake so it never turned by hand even when working fine previously. The brake makes it easier to change sandpaper. I have not taken it apart more than the video shows to see if I can disable the brake. But I doubt there is a problem there because it starts slowly easily then speeds up like it always has but a few seconds later it clicks and the brake applies. Several seconds after that I hear the click in the switch when it resets itself (I guess).

 

[foghorn1966]

One of the adjustments on the overload block get turned out of adjustment? There should be a label in the cover of the contactor enclosure that should give guidelines for the settings depending on the full load amps of the motor.

 

[matt_i]

One of the adjustments on the overload block get turned out of adjustment? There should be a label in the cover of the contactor enclosure that should give guidelines for the settings depending on the full load amps of the motor.

I think this is it ^. I can't tell which adjustment to turn for more current though.

First, though, it would also be very good to tighten all of the screw terminals that you can access. If one of those gets loose and it starts arcing internally, heat will spread very fast thru the copper wiring, and its heat that ultimately trips the overload.

However if you are sanding more aggressively then perhaps the motor is also using more current than before.

 

[Bogie1632]

Can always use a multimeter to check voltages and see where you loose it when it shuts off on it's own. I've had a few switches go bad on tire machines, but those tend to get cycled a lot. Multimeter helps find the culprit quick.

V/R
Bogie

 

[greg13]

Have you called Grizzly? In the name of customer service they may help you out.

 

[ALinCarolina]

I did call Grizzly last week and the tech was very nice and described the points, etc. and suggested to take the cover off and watch it run. They also have a good video on their youtube about adjusting the points. Tomorrow I hope to have time to get into it deeper, check capacitance, etc. and can call them next week with what I find.

It hasn't been used but a few minutes at a time and with this problem there was no sanding done at all since it only runs for a few seconds. The fact that after sitting it runs a few seconds longer and then with repeated starts it gets shorter and shorter makes me worry about a shorted winding or something causing it to trip the overload breaker. But this is not my field and I have not worked on electric motors much. Many more electrical experts here on GJ than anywhere else though!

 

[j.butterworth7]

adjust overload settings far left dial bit at a time, settings probably correct for when motor running under normal conditions but will pull more curent on start-up, probably just a bit more than what overload is set at.

 

[pcmeiners]

" The fact that after sitting it runs a few seconds longer and then with repeated starts it gets shorter and shorter makes me worry about a shorted winding or something causing it to trip the overload breaker."

Since repeat starts shut down the motor quicker, to me this sounds normal if the overload is set to low. Repeated starts will warm up the windings, warm wires draw more current.

 

[fatfillup]

I don't think the overload has anything to do with this problem. The motor is not coming up to speed quickly enough and pulling too many amps for too long trying to start. The overload is doing its job.

I agree with above about checking the current. Test your incoming power at L1 and L2 on the contactor(if those are the ones used) before starting and check again while starting. you should have a voltage drop but likely no more the 15 volts or so. If it is far more then that, check your incoming power supply. Possible issue there.
If you don't have a big voltage drop, check the voltage at T1 and T2 on the contactor while starting. If it is the same as L1 and L2, then your contactor is likely good.

Next test the capacitors and make sure they are ok.

If they are good, then motor is likely the issue.

Is the machine 110 or 220 volt?

 

[ALinCarolina]

It's 220 V. I will be off the next few days and will open the machine and motor and check the voltages and the capacitors.

 

[ALinCarolina]

Update so far: I opened the machine and motor and found the start capacitor had oil leaking all over it. It tested at 46 MF instead of 150 MF. I have ordered a replacement so will see how that works out.

 

[gayler]

Update so far: I opened the machine and motor and found the start capacitor had oil leaking all over it. It tested at 46 MF instead of 150 MF. I have ordered a replacement so will see how that works out.

Sounds like your on the right track.

 

[Robbie B]

Sounds like your trip circuit is set too low or gone bad. Amp clamp with min/max will show you draw when it trips.


Sent from my iPhone using Tapatalk

 

[EZ_Garage]

Bad start caps are very common. Sounds like you got it figured out.

 

[ALinCarolina]

update: I replaced the capacitor and it now runs fine. Hope it keeps it up.

 

[ALinCarolina]

Thought I would update this thread in case it could help others in future. I ended up going through a couple more start capacitors. With the cover off I could see the points not opening and watched the start capacitor start smoking and leaking. I tried adjusting the centrifugal switch so it was just touching closed but still wouldn't open. Not sure why since I could easily move the weights manually with no binding. I first replaced the springs with some lighter ones from my box of springs but they were too light and wouldn't even close the points.

I called Grizzly and all he suggested was to replace the centrifugal switch so I had him order me one and paid him $23 or so. But I figured the springs on the new one were probably just as strong and would act the same so I tried something a little nutty.

I cut some rectangles of 1/16" lead, drilled a hole through each weight on the switch and bolted several pieces of lead to each. It works great (so far anyway). The added weight causes the switch to open just as the motor starts to gain speed. I called the company back and cancelled the order.

I told a friend who also does goofy fixes and he said: "Sounds like something I would do!" And I figure it might fit into the GJ mindset.

 

[marinusdees]

For $23 I'd order the switch. Just me. Those things are somewhat calibrated to the motor to open at a percentage of full rpm. The consequence of some fault would be excessive heat. Did you inquire as to the cost of a new motor??

 

[matt_i]

Turning lead (Pb) into gold (Au) is a long-lost art great fix!!!

 

[ALinCarolina]

Turning lead (Pb) into gold (Au) is a long-lost art great fix!!!

Ha. Yes, modern alchemy!


Well, the $23 didn't bother me but I suspected the springs would be the same as the one I had. It has very, very little hours on it and the engineer said the points should open almost instantly. (I mostly use my Grizzly edge sander). If there is a bad winding then I will end up replacing the motor anyway and will buy local. My buddy ran it today for a good while and worked flawlessly finally. I'll update if anything else happens.