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Motor for Powermatic 3520B

K

Karl Stauber

Joined
Oct 22, 2019
Messages
27
Likes
1
Location
Winston-Salem, NC
I recently moved with my 14 year old lathe. The movers dropped the headstock and the spindle is frozen. I want suggestions on how to fix the problem. I have had trouble seeing if Powermatic still sells this motor and assembly.
 
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If your lathe has a spindle lock, ensure it isn't engaged. If that isn't the problem, remove the drive belt to rotate the spindle by hand and then the motor shaft by hand. If either one is dragging or binding, you will be able to focus your troubleshooting using a systematic process of elimination. If both the spindle and motor shaft turn freely you should verify that the VFD is providing power to the motor. If your lathe has a remote stop switch, it is a likely suspect. Those switches aren't environmentally sealed and are notorious for dust getting inside and preventing the contacts from making a solid low-resistance connection.
 
Richard Coers said:
Did you take the belt off to troubleshoot? Good be as simple as removing the fan shroud on the motor.
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This is another possibility. Seized spindle (not rotatable by hand) is almost certainly a mechanical problem, not electrical. Look for scrapes or dents to tell you which side took the impact with the ground. That will provide some clues where to start looking for the problem.

Also, good movers have good insurance. They will probably pay for repairs without much fuss. If you are able to do the repairs yourself they’ll probably be willing to give you a break on the moving cost.

I’ve done a lot of furniture repairs over the yers for a local moving company and they were always eager to keep their customers happy.
 
Richard Coers said:
Good be as simple as removing the fan shroud on the motor.
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If the shroud is dented enough to jam the fan, it is very important to replace the shroud before operating the motor. The shroud creates laminar airflow over the motor to keep it from overheating. Without the shroud, the motor can't be cooled.

I know of one incident where movers dropped the headstock of a Powermatic 3520 causing it to crack. That's probably the worst possible thing that could happen.
 
Fan shroud has a significant dent. Can probably hammer out. Shaft is frozen. Have pulled the motor. Hate to open the motor. May leave that to someone who knows what they are doing. Stay with Powermatic authorized repair shop or go with local electric motor repair firm?

Movers were awful. I stored the lathe for most of a year, awaiting new shop completion. Should have inspected equipment in storage. Didn’t and that is on me.

Shop without lathe is like a Ferrari without tires.
 
The fan shroud is most likely pushed up against the motor cooling fan locking the motor shaft in place. The motor fan shroud can easily be removed from the motor to remove the dent in the shroud. You will also need to inspect the motor fan for damage, many of these are made from plastic and can easily be damaged when the shroud gets damaged. Several screws and the shroud cover comes off.
 
Plastic fans typically produce increased airflow compared to some of the flimsier aluminum fans. HERE is a link to cooling fans on Amazon.

High-efficiency motors made in the last decade or so have a very small clearance between the rotor and stator. The downside is that damage caused by dropping the motor might be sufficient to cause the rotor to drag against the stator.
 
We.need more info. Loosen the Belt to see if the spindle is free. If not trouble shoot that. If the spindle moves can you rotate the motor by hand. Could be a pulley is out of position. Could be spindle lock. Could be the bearings got knocked If it landed on the spindle. A lot of possible causes. More trouble shooting needed.
 
Richard Coers said:
So now you have to look at the guts of the motor. Bill told you what to look for. Motor (3520B-232) is $1,110 and available in 2-3 weeks. https://www.ereplacementparts.com/p...dturning-lathe-parts-c-32549_32637_32638.html
Or $920 at https://www.mmtoolparts.com/powermatic-motor-3520b-232
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Yikes!! Holy sticker shock, Batman. I haven't been keeping up to date on motor prices. I know that the cost of everything, post-pandemic, is through the roof, but this is staggering.
 
Brent@TurnRobust said:
Any competent electric motor shop should be able to diagnose your motor issues and give you a repair estimate. The motor on the PM3520 is a non-standard motor - for one thing it has an extra long shaft. So you'll either need to get the one you have repaired, or get a new one from PM.
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The willingness to help and participate by this American company is one reason I buy from them every chance I have!
 
Bill Boehme said:
Yikes!! Holy sticker shock, Batman. I haven't been keeping up to date on motor prices. I know that the cost of everything, post-pandemic, is through the roof, but this is staggering.
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My thought exactly! But it's a custom motor with a new lathe model replacing it. Makes it tough for the thousands of owners of the B model out there!
 
I worry that the inverter may have been damaged. Anyway to check the inverter before repairing and reinstalling the motor? Looks like the inverter for 3520B is no longer available. Suggestions?
 
Having worked on Mustard Monster VFDs, I recommend not doing anything to 'check' it at this point. If you do the wrong thing and change one of the settings, it's a very thorny path to get back to where you need to be. Doc Green's troubleshooting suggestions are helpful, if you have a problem, but pray you don't need them.

As Richard says, if you plug it in with the motor disconnected, the rpm display will light up, but that's a separate circuit from the VFD functions, and therefore doesn't prove anything other than that you have power. If the screen on the VFD itself shows 50 or 60 (hertz), you are probably OK. If it remains blank or blinks with an error code, you may be in deep doodoo.
 
I appreciate everyone’s suggestions. Took to local motor repair place today. They will give me feedback in about 2 weeks. His immediate review showed me 2 cracks in the case but he said that may not be fatal. We will see. I’ll post the results when I know more.

Any additional thoughts welcome.
 
Richard Coers said:
My thought exactly! But it's a custom motor with a new lathe model replacing it. Makes it tough for the thousands of owners of the B model out there!
Click to expand...

The B model motor appears to be a standard NEMA configuration with rolled steel frame and C-face mounting. I agree with everybody that he shouldn't worry about the inverter for now. If it powers up and doesn't display an error code that would be a good sign.
 
For the Delta S1 inverter, there are three inputs required for the inverter to operate. A Run command, A Direction command and A Speed reference command. There are 3 LED’s on the left side of the display for the RUN, FWD and REV command. With the E-stop button out, Run Position, you should have the RUN LED. Push the button in, E-Stop position and the RUN LED should go out.

With the E-Stop in RUN position and the RUN LED displayed, change the position of the FWD and REV switch and the corresponding direction LED’s should change status. There is an alfa numeric display on the control face that can be programmed to indicate several things. I believe the default is F for frequency input to the Inverter. If you have the display starting with an “F”, slowly rotate the speed control potentiometer from minimum “0” display to maximum about “135” and back to “0”. The display numbers should increment and decrement smoothly and without any noticeable skips. Yes, the Inverter is programmed to overdrive the motor to about 135 Hz. The inverter will not operate w/o the “F” speed reference input even if the e-stop is working, in the RUN position and you have a FWD or REV signal.

If any of the above inputs are missing or the speed reference is unstable, those inputs need to be corrected. I suggest you run this test first to try to pinpoint the problem before you poke around in the wiring and/or blow out switches or the potentiometer with compressed air. It should take less than 30 seconds to perform once you have done it.
 
Bill Boehme said:
The B model motor appears to be a standard NEMA configuration with rolled steel frame and C-face mounting. I agree with everybody that he shouldn't worry about the inverter for now. If it powers up and doesn't display an error code that would be a good sign.
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The shaft is 6" long off the face. Much longer than standard.
 
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Karl Stauber said:
Does the 3520B run on 208 volts?
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The lathe runs on standard single-phase 240 volts 60 Hertz power. The inverter (VFD) converts it to three-phase power for the motor at a frequency that is determined by the speed control knob on the headstock. The voltage to the motor isn't necessarily 240 volts, it is progressively reduced at slower speeds so that the motor's iron core isn't magnetically saturated.

I assume so, it's definitely a 3 phase motor. I don't know what the output voltage from the VFD is for sure. Why, are you thinking you can still find an alternative motor? There absolutley is no generic replacement.
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It might be possible to use the rotor with the six-inch shaft from the old motor in a new motor of the same frame size from the same manufacturer.
 
The stator and rotor core sheet thickness appear to be thinner than normal 60 HZ motors. Thats a good feature since the motor is driven to 135 HZ.
 
Bill Boehme said:
It might be possible to use the rotor with the six-inch shaft from the old motor in a new motor of the same frame size from the same manufacturer.
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That's what I call a really long shot! I would assume all this angst about the motor and cost is a non issue when Karl contacts the movers insurance company.
 
End of the story. Motor could not be repaired. Powermatic authorized repairers would not look at it. Had an electrician look at the inverter. He was concerned about its reliability, given the headstock had been dropped and damaged. I have ordered a replacement PM2020. Decent price from Rockler but trouble getting info from them on shipping date.

Thanks for everyone's thoughts and suggestions.
 
Karl Stauber said:
End of the story. Motor could not be repaired. Powermatic authorized repairers would not look at it. Had an electrician look at the inverter. He was concerned about its reliability, given the headstock had been dropped and damaged. I have ordered a replacement PM2020. Decent price from Rockler but trouble getting info from them on shipping date.

Thanks for everyone's thoughts and suggestions.
Click to expand...
Can’t you order directly from Powermatic?
 
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