Is my motor fried?

W

Watchwatch

Registered
Registered
Joined
Mar 22, 2020
Messages
175
I bought a wells index 747 at auction. I’m trying to power it with a TD200 VFD.

The mill the spindle will turn for a short time, but very slowly. Then I get an overcurrent fault.

I am getting continuity from each leg off the motor to ground. According to my research, this is a motor short?

Any help would be much appreciated. I have limited knowledge about electricity.


Sent from my iPhone using Tapatalk
 
Hi and welcome,

You might have many things wrong but if there's continuity and it does turn a little it's probably not fried. One of the things some on here recommend is not using VFD's for very old motors since the way they provide 3 phase can possibly harm old insulation winding.

You may want to consider using a static or rotary phase converter for your machine rather than the VFD.

What's the HP of your motor and FLA for the VFD you're trying to use, hopefully you're not trying to use 115v single phase to power the VFD.

John
 
What model VFD?

It looks like TD200 goes from 1.8 to 10.5 FLA.

John
 
Continuity to ground is a bad thing and is most likely causing the problem. A "rule of thumb" is that resistance to ground should be 1000 ohms per volt. Using that rule would require at least 240,000 ohms to ground on a 240 volt motor. Motors that fail this "rule of thumb" should be rewound or replaced. The best way to measure this is with a meg-ohm meter (sometimes called a "megger"). If you are seeing continuity with a multi-meter, the motor is toast.
 
I misread the original post thinking continuity was internal, not to ground. Yes, time to find a new motor. Good news is you have the chance to choose an inverter duty unit.

John
 
den-den said:
Continuity to ground is a bad thing and is most likely causing the problem. A "rule of thumb" is that resistance to ground should be 1000 ohms per volt. Using that rule would require at least 240,000 ohms to ground on a 240 volt motor. Motors that fail this "rule of thumb" should be rewound or replaced. The best way to measure this is with a meg-ohm meter (sometimes called a "megger"). If you are seeing continuity with a multi-meter, the motor is toast.
Click to expand...

3 wires coming off the motor. Omhing each wire individually, ground to bare metal on the machine.

Am I testing correctly?


Sent from my iPhone using Tapatalk
 
You really only need to test one lead to ground. All three connect though the windings so if one is shorted to ground, all will read continuity to ground.
 
Is your motor still connected to the VFD while you are taking these readings? If so, disconnect the motor from the VFD and check it again.
 
Yes with motor disconnected from VFD you should read AT LEAST 250,000 ohms from any of the three motor leads to ground. A new motor would be a couple million ohms or more
-Mark
 
  • Like
Reactions: Z2V
You must log in or register to reply here.
Back
Top