PM3520 Acting Strange

[Ed_McDonnell]

I go out to the shop this morning and turn on the lathe (PM3520B). Nothing happens. Check the power (got power) and the speed control (it's not at zero). I turn the handwheel and the spindle spins freely.

I click the on / off switch a couple times and no go. I unplug the lathe, wait a minute and plug it back in. Still won't run when I turn on the switch, but if I turn the handwheel while the switch is on, it starts to run.

I repeated the "turn on" and "spin by hand" to start 3 times. The fourth time the lathe started right up when I turned on the switch. It worked fine the rest of the day.

I searched around, but couldn't find anyone reporting a similar type problem. Anyone experience anything like this or know what (if any) the problem might be?

I would call PM, but that will have to wait until Monday.

Ed

 

[john lucas]

That's a new one on me Ed. I would check all the connections going to the speed control switch. That may not be it but I'm not sure what else it could be. I've seen loose connections cause weird things in other machines.

 

[Ed_McDonnell]

Thanks John. I'm just hoping it's not something with the electronics. It can't hurt to open it up and look at the switch connections. I'll do that this morning.

Ed

 

[KurtB]

Pm3520

Ed,
Did you check to see if you have a reset button on the VFD controller?
Kurt

 

[Ed_McDonnell]

Hi Kurt - There is a "Stop / Reset" button on the controller, but I don't have any documentation and the PM manual pretty much just says "DON'T TOUCH THE BUTTONS ON THE CONTROLLER".

I just unplugged, waited and replugged, hoping that would reset anything needing resetting. (It works for my cable modem!!). That didn't make any difference yesterday.

The problem eventually went away yesterday.

By the way, the lathe is running fine so far this morning.

Ed

 

[Malcolm Smith]

I'm not familiar with that particular lathe but it certainly sounds like it simply needed re-setting of the switch. Usually this is required when there is overload such as one has turning on a lathe when rotation is locked or an irregular block of wood runs into the tool rest.. If it continues to happen and no overload has occured, I would contact the manufacturer.

Malcolm Smith.

 

[Richard Baker]

Ed,
My 1642 (essentially same motor and controller, I think) did the same thing after a power outage. I opened the breaker and let it sit for a while and contemplate its tailstock without power. When the breaker was turned on again the lathe operated normally. But cannot remember if I pushed a reset button. Does indeed seem as though it just needed to "reboot" its tiny litle mind.

 

[Ed Reiss]

I go out to the shop this morning and turn on the lathe (PM3520B). Nothing happens. Check the power (got power) and the speed control (it's not at zero). I turn the handwheel and the spindle spins freely.

I click the on / off switch a couple times and no go. I unplug the lathe, wait a minute and plug it back in. Still won't run when I turn on the switch, but if I turn the handwheel while the switch is on, it starts to run.

I repeated the "turn on" and "spin by hand" to start 3 times. The fourth time the lathe started right up when I turned on the switch. It worked fine the rest of the day.

I searched around, but couldn't find anyone reporting a similar type problem. Anyone experience anything like this or know what (if any) the problem might be?

I would call PM, but that will have to wait until Monday.

Ed

It is very likely that the motor starter capacitors might be the cause of the problem😎If they are weak it won't provide enough "ooofff" to get the motor going.

 

[Ed_McDonnell]

I checked all the switch connections and didn't see or feel anything that seemed like it might be a problem.

I usually unplug the lathe when we are expecting lightning and I generally don't work on the lathe during lightning storms. Unfortunately, we've been having 4 - 5 hours of intense lightning storms every afternoon / evening for the last couple of weeks.

I was losing too much turning time so I've been working during the storms. We have underground utilities, so the electricity is pretty stable during the storms, but we had a couple real close hits the other day. Maybe we got a little surge or something that confused the controller.

Anyhow, it worked flawlessly all day today. I don't know how to test the motor capacitors, so as long as it keeps on working I guess I won't worry about it.

Thanks for all the help with this problem.

Ed

 

[Bill Pottorf]

Lightening!

Ed, working on your lathe during storms is asking for real trouble. I always unplug the lathe, computers (even though I have an ups), and any other electronic devices which can be unplugged. Last month my wife and I were watching the news on tv (not unplugged), when an unexpected bolt hit the house behind ours. We have underground stable utility as well. All of the lights went up bright and maybe the hair on our heads stood up on end. Then all power was shut down at the transformers - lights out!. Fortunately, we did not suffer any damage but the house behind was on fire and largely lost to liveability. The lathe was unplugged, as always when I leave the shop.

My point here is that the vfd on your lathe is the most expensive part of the lathe, costing a considerable amount to replace.

I sometimes hit the emergency off switch by accident on my lathe. This turns off the vfd and takes a considerable time to reset. There is a reset button but have to unplug the lathe as well. If you have an emergency off switch, check to make sure that it is in the reset position and allowing free reign for the vfd to control the motor. Just a thought. Hope you get it solved soon.

Happy turning - Bill

 

[Ed_McDonnell]

Bill - I agree 100% with what you are saying, but if we unplugged everything every time we heard thunder down here in South Florida we would have everything uplugged for about 5 months out of the year.

Mabye I got lucky this time and just got a warning shot across the bow. I think I'll stop turning during lightning storms, but it sure is hard to go for weeks on end with no turning. The storms have been relentless this year. I suppose I could go on the night shift and turn from 2:00am - 10:00am. It would even be a lot cooler then. Hmmmmmm...........

Wish I could find an affordable UPS for the lathe. The only 230v UPS I could find were for foreign markets where 230v is standard and nothing that would handle the lathe power requirements.

Ed

 

[Dick Latshaw]

Mabye I got lucky this time and just got a warning shot across the bow. I think I'll stop turning during lightning storms,

Good idea, Ed. We took a hit about five years ago. Did in the dishwasher and disposal, and did about $2000 damage to the main panel, breakers and meter. Hate to think what it would have done to the VFD if it had been plugged in. I don't turn during storms (we get our share:mad🙂 and unplug all tools when I'm not in the shop ...er, studio.

 

[MichaelMouse]

I
Anyhow, it worked flawlessly all day today. I don't know how to test the motor capacitors, so as long as it keeps on working I guess I won't worry about it.

No worries. You're inverter VFD.

One of the nice things you can do for yourself is to fit the lathe with with a knife switch. A few inches of air gap will discourage it as a passage to ground. It will also gain you peace of mind to put one on the shop subpanel (not the lights), so you can shut off or lock out power when the kids or grandkids are around.

 

[n7bsn]

...........
Wish I could find an affordable UPS for the lathe. The only 230v UPS I could find were for foreign markets where 230v is standard and nothing that would handle the lathe power requirements.

Ed

Ed, you really don't need a UPS (besides one large enough would be, well, even larger then your lathe).

All you need is Panel Mount Surge Arresters. I bought mine at a big-box store years ago, and have not lost a piece of gear since then.

What they are is really are is very large (conventional) surge arresters that connect to both sides of your main power. Since they are mounted right where the power comes in, they have a chance to act, before the surge makes it to your equipment.



TTFN

Ralph

 

[Jake Debski]

Bill - I agree 100% with what you are saying, but if we unplugged everything every time we heard thunder down here in South Florida we would have everything uplugged for about 5 months out of the year....................................................................................................

Ed

You said you went "out" to your shop/studio. If it is free standing, or otherwise isolated(attached garage) you could install a double pole knife switch(pull switch) between your panel and your shop. One simple pull on your way out and the reverse on your next trip into the shop. Reasonably inexpensive protection, and it will save you the need to "unplug" every time there is thunder and lightning.

 

[Richard Baker]

Am told that in this area building code requires a main breaker/disconnect mounted outside the house where emergency personnel can operate it if necessary. I installed a secondary main breaker next to the above, whence the power lines proceed underground to the shop building. Have actually pulled this breaker a couple of times when particularly nasty weather was impending.

But not lately. Heard some thunder once, but virtually no rain for two months.

 

[n7bsn]

You said you went "out" to your shop/studio. If it is free standing, or otherwise isolated(attached garage) you could install a double pole knife switch(pull switch) between your panel and your shop. One simple pull on your way out and the reverse on your next trip into the shop. Reasonably inexpensive protection, and it will save you the need to "unplug" every time there is thunder and lightning.

Please understand that a knife switch (as opposed to a disconnect box) would violate just about every electric code there is, and would probably cause your insurance company to avoid any liability claim related to it.

 

[Jake Debski]

Please understand that a knife switch (as opposed to a disconnect box) would violate just about every electric code there is, and would probably cause your insurance company to avoid any liability claim related to it.

Once again proper nomenclature has risen up to bite me in the butt. I have a manual, fused, disconnect box between my house and my barn. Its internal workings resemble an old fashioned knife switch. It was installed by me and inspected at the time of construction. My insurance company has also inspected the premises since that time. If my previous post caused any confusion or misunderstanding I apologize.

 

[Jerry Hall]

Remote Switch?

If you have a remote switch I would bet you are getting the beginning of dust problems. Check the mustard monster site for lots of discussion. Apologies if discussed in thread. Just found your post in a quick check while in France. Next time bypass the switch with power off! Then see if it works.

 

[loberg]

Back to the Original Question

I had the same problem with a motor on a band saw. The local electrical repair shop told me there is a relay type switch inside the motor to control the capacitor start system. He said occationally blowing out the motor will help the problem. I have put shields over the top of the motors to prevent dust from getting into the motor. The motor acted just like yours and I thought the capacitor was bad, but it was not. The "switch" was the problem. Hope this helps.

 

[MichaelMouse]

I had the same problem with a motor on a band saw. The local electrical repair shop told me there is a relay type switch inside the motor to control the capacitor start system. He said occationally blowing out the motor will help the problem. I have put shields over the top of the motors to prevent dust from getting into the motor. The motor acted just like yours and I thought the capacitor was bad, but it was not. The "switch" was the problem. Hope this helps.

Horse(power) of a different color.

The variable-speed electronics in the PM3520 are far beyond that centrifugal switch in a standard capacitor-start induction-run motor. I rather suspect that some may not realize that arcing can pit the "points" on the centrifugal switch, a condition easily remedied by some 400 SiC paper folded and drawn through the pair a few times. I say this in the interests of "beginner" acknowledgment, just as I say that damp sawdust in the capacitor housing can steal the juice as easily as either of the actual switch contacts. I like to take some stickyback foam of the type used for sealing around windows and use it as a dust barrier between the motor housing and capacitor bulge. Then the twice a year preventive maintenance routine can keep pace with infiltration.

Please understand that I speak in principle, and the precise terminology may differ just as above, where the creation of a substantial air gap by a large hinged device as in a knife-type switch was the principle if not the proper nomenclature.