powermatic 3520A inverter problem

[jay christopher]

I have 3520A lathe that turns 1/4 turns & stop .I called Powermatic service they said it is the motor had the motor repaired ,clean & checked ok? recalled, Powermatic ran the test , they still say it s the motor HELP?

[John K Jordan]

I have 3520A lathe that turns 1/4 turns & stop .I called Powermatic service they said it is the motor had the motor repaired ,clean & checked ok? recalled, Powermatic ran the test , they still say it s the motor HELP?

Know anyone with a PM who would let you test your motor on their VFD?

JKJ

[Dennis Ford]

It is a three phase motor, they are very simple machines with not much to go wrong. Two bearings, a fan and copper wire. A bad bearing (very bad) might lock up when the motor starts turning, this would be easy to diagnose. The fan housing might stop the rotor from turning if bent or if the fan has moved on the shaft. A winding shorted to ground might trip the inverter. Not much else normally goes wrong with 3 phase motors.

[jay christopher]

Know anyone with a PM who would let you test your motor on their VFD?

JKJ

can find one

[jay christopher]

It is a three phase motor, they are very simple machines with not much to go wrong. Two bearings, a fan and copper wire. A bad bearing (very bad) might lock up when the motor starts turning, this would be easy to diagnose. The fan housing might stop the rotor from turning if bent or if the fan has moved on the shaft. A winding shorted to ground might trip the inverter. Not much else normally goes wrong with 3 phase motors.

no it is single phase with a inverter to 3 phase

[John K Jordan]

no it is single phase with a inverter to 3 phase

The inverter is single phase but the motor itself is 3-phase. You can run any 3-phase motor from single phase power with a properly sized VFD/inverter.

What Dennis wrote seems to cover most of what can go wrong with a 3-phase motor. If you loosen the belt you should be able to spin the motor easily by hand. If you disconnect the power leads to the motor you can figure out if one or more winding is shorted internally or to ground. You can even rewind it yourself. Google brought this up first: https://www.instructables.com/id/Rew...3-Phase-Motor/ I didn't go through it but from a glance it might have good information on diagnosing a problem.

JKJ

[Reed Gray]

Hmm, did you have the motor repaired locally? If so call that shop and ask about the phase converter. The on/off switch, and the variable speed knob do go bad after a while. The motor needing repair would most likely come from very heavy duty use. I did wear out the headstock spindle bearings on mine after about 5 years. I was turning mostly chain sawn blanks, and didn't use the tailstock. Oh, those parts can be sourced locally rather than from PM. Also, the techs at PM are most likely reading from a manual rather than having any actual first hand knowledge of the tool.

robo hippy

[Robert Edington]

Do you use the speed control a lot i.e. to stop and start it? As mentioned, might be the pot.
I have a 3520a also.
RP

[JohnC Lucas]

you might possibly have something binding somewhere. Bad bearings were mentioned or it could be something blocking the spindle from turning or putting excess pressure. that inverter will stop the lathe if it things something is keeping the spindle from moving. I have had roughly the same symptom when I do something stupid like having the wood hit the tool rest or leaving my homemade index system engaged when I turn on the lathe. Check and see if everything is free to rotate with no pressure at all.

[Dick Strauss]

Does the VFD display an error code?

[Bill Boehme]

The tech support people at PM might be right. The inverter might be sensing a fault condition such as current that is higher than it should be or leakage current or ground fault current, etc. Ask them to elaborate on their diagnosis. Also, ask them if a new motor turns out to not be the right answer will they take the motor back.

[Bert Delisle]

I have 3520A lathe that turns 1/4 turns & stop .I called Powermatic service they said it is the motor had the motor repaired ,clean & checked ok? recalled, Powermatic ran the test , they still say it s the motor HELP?

Check the off switch push button, if it is momentary, like on my Vicmarc, periodically the fine dust causes the off button inner workings to stick in the stop position. Can't tell from outside. The start button sends a start command to the motor which kicks the motor but the stuck stop button sends the stop command so as soon as you release the start the motor stops again. I periodically have to clean mine. Same symptoms as you described.

[John K Jordan]

Check the off switch push button, if it is momentary, like on my Vicmarc, periodically the fine dust causes the off button inner workings to stick in the stop position. Can't tell from outside. The start button sends a start command to the motor which kicks the motor but the stuck stop button sends the stop command so as soon as you release the start the motor stops again. I periodically have to clean mine. Same symptoms as you described.

On the 3520B (and the Jet 1642) the on/off switch is not momentary, but switches a low-voltage control line in the VFD. I suspect the 3520A is the same - it looks like the same switch. But dust can still be a problem, but preventing the lathe from starting at all. I had to disassemble the switch on my 1642 and on a friend's Jet mini to clean out the fine dust. I lube with dielectric grease and seal the outside of the switch to prevent future dust intrusion.

JKJ