Mill spindle comes to speed, click, slows down, click, repeat

dumpsternaut

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Hello,


I have a motor problem on my mill that I'm hoping is common or straightforward.

I guess I'll do a summary first, then proper intro, specs, and explanation:

  • – The spindle gets up to maybe about full speed, then <click> slows down almost like no power, then <click> process starts over.

  • – It's the type with both a startup and a running capacitor. I don't have much experience in this area. I'm hoping the <click> is not a thermal breaker (like it sounds), and instead that maybe it's an internal relay switching from Startup to Run mode and the capacitor(s) simply need replacing...? Or maybe it is a thermal switch but the heat is still because of bad caps?
  • – I'll say this: When it speeds up and <click> and you turn it off... it still goes <click> anyway, one more time, like a cooled off thermal strip resetting :( even powered off.

The rest of the facts:


I recently acquired one of those somewhat white-label benchtop milling machines (mill drill) called a ZX7025, offered by multiple companies such as Luzhong (mine's used and a little modified, so who knows) :
type:
luzhone-ZX7025-Vertical-Drilling-And-Milling-Machine.jpg

pics from mine, actual unit:

IMG_3537.JPG
IMG_3538.JPG
mill motor model zx7025.pngmill motor label1.png

It has a 1 hp motor currently wired for 110v. It is quite simple with no brain or complicated wiring harness, seemingly just a power cord, a switch, and a motor with the two capacitors. No electrically adjustable spindle speed, just a static max speed and manual belt pulley placement options.


An honest friend claims it was working fine at first on his 110v wall socket but after sitting it does as described. It does, indeed, have a 110v plug on it.
Here's a better look at the goes-inta:
mill motor wires close2.JPG

I really appreciate any insight on the matter. I'd like not to have to buy and install a new motor.

I'll answer any questions I can, will watch for replies, and I look forward to posting a bit about the interesting new woodwind instrument craftsmanship work I plan with the machine, sharing a little of my own ingenuity with things I've come up with.

Thanks much,

Jeff
P.S. SAFETY --
While my technical knowledge in this area is fuzzy --
my safety procedures are not fuzzy
I have high voltage vintage radio transmitter experience, so I promise to be aptly careful, discharging caps and I have insulated instruments including a grounded probe with insulated shaft and handle. Thanks again.
 
I see that the motor data plate says 220 volt and no mention of 110, although most motors of this type can be wired for either voltage.
So that could be it, or maybe there is an actual problem with the centrifugal switch in the motor, or a capacitor problem.
Really need to verify if it's wired for the correct voltage first. No other wiring data with the machine?
A motor of that size should really be run on 220 anyhow. (240 actually these days) The current draw on 110 would probably trip most common 15 amp breakers, assuming it could be wired for 110; the problem you describe sounds suspiciously like it's running on half voltage.
-Mark
 
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Thanks for your reply!

You said a motor of this size should really be run on 220v. I suppose it's not out of the question to run it on 220v, as it's not terribly far from it.

I can try to find more wiring data on a ZX7025 but I wouldn't be 100% sure that it was the same anymore. I was wondering if it would throw the breaker but it didn 't here and he said it wasn't at his house (who knows if it's wired correctly though)... threw a mini-breaker on a cheap powerbar at his house, LOL.

Yeah... I did notice the plate didn't mention 110v but I didn't know if that labeling was common for other motors that were okay to re-wire for 110v..?
Now that you mention it, my 3/4 HP planer motor says either or!

While it would have been great to hear,
"It looks wired correctly but is symptomatic of a bad running capacitor",
...there seems no getting around it -- I need to learn more about this motor and its correct wiring options and what they are.

You did mention "the centrifugal switch" -- so is that how a typical 2-capacitor motor decides to switch from "startup" mode to "run mode" -- a certain speed trips a centrifugal switch? That makes me sort of happy because it explains the second click happening even if powered off (when the spindle slows back down it clicks again, with or without power). Doesn't mean it's some kind of overheated thermal breaker. I like that.

He claims it was wired for 110v and was running fine for some time and just started this (even showed me parts me milled), and that is why I wondered if it was the running cap...
like maybe --
"Everything is okay until it gets to speed and clicks but then it slows back down until it re-enters startup mode because the running capacitor is bunk...?"

He wanted to call off the sale and fix it first and I was the one who pressed on to pay and take it, because I can't wait weeks for him to get around to it, or lose it to someone else with nothing like it for reasonable sale ever around here.

I'll learn what I can - thanks for your thoughts!
 
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hmmm... I found ads for Y90S-6 motors and they say
Three Phase
380V or Any Voltage Between 220-760V
Nothing about 110v so I'm wondering if it's not a good candidate for the 110v single phase re-wiring trick -- provided they even did so correctly -- because it seems if they did, and it was drawing enough current to run right, esp. after seeing these specs, it seems it would pop the 15amp breaker as you stated)?

It doesn't strike me as coming to speed fast enough, either. Seems sluggish compared to mills at work.
 
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The behavior of your motor makes me think that the repeated clicking you hear is the centrifugal switch kicking in (when it slows down) and out (when it's up to speed). I'd guess that the start winding and capacitor are OK, but there's something fishy about the run winding. Might possibly be that it wants to be fed 220 instead of 110. I've had 220 motors where the start winding only gets 110 (because it's connected to the "center tap" of two run windings wired to 220 in series). If the run winding is expecting 220 and only gets 110, it might have just enough oomph to help the start winding get the motor going, but can't sustain it when the centrifugal switch turns off the start winding, and it's left on its own.

About the only thing i can suggest is for you is to ohm out all the windings, looking for opens. I'm not by any means a motor expert, so you'll have to wait until one of them posts and gives you a complete answer. But by then you'll have more information to offer.
 
He claims it was wired for 110v and was running fine for some time and just started this (even showed me parts me milled), and that is why I wondered if it was the running cap...
like maybe --
"Everything is okay until it gets to speed and clicks but then it slows back down until it re-enters startup mode because the running capacitor is bunk...?"

This was my thought when I read your first post. Hopefully you have a multimeter, check the caps.
 
... or it could be a bad "RUN" capacitor. i.e. your start capacitor starts it spinning (it is good), but once it switches to the FAILED run capacitor, the motor stops applying power. Then when the RPMs drop below a certain RPM figure, the START capacitor is engaged again... causing the motor to spin back up (to the threshold where the RUN capacitor kicks in).

It could also be bad contacts on the centrifugal switch which connects the RUN capacitor... but testing the capacitor would be the easiest first step.
 
It's not reaching a high enough speed to stay running. It looks like a single voltage motor to me. Also, check the voltage ratings on the two capacitors- If they are both rated at 250 volts or more then it's likely a 240 volt-only motor
I agree with John in post #5 as far as "oomph"
-M
 
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Thank you all for your time and thoughts.
I'm a heck of a lot better off than I was all alone, and this gives me more well-lit paths to pursue.

Ironic side note:
Even though the weight and cumbersomeness of this unit was 150% as much as my wife and I had any business transporting (where there's a will there's a way)...
... the way I hurt my back the same day was actually helping a young firefighter move a big fiberglass motorhome moulding several feet.
So I'm hobbling pretty badly accepting prayers to be in good enough shape to help out my own folks (pushing 90) up the road stay in their home.

Gives me some time to brush up on electrical stuff, though.

In earnest:
Thanks again!
 
Maybe look at your planer and see how it is wired. Maybe the guy that had it rewired his 110v outlet for 220v :eek 2: I have seen some crazy stuff over the years.
 
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