VFD trouble shooting phasing

Hi, I'm new to the site but already finding it a font of useful knowledge and discussion.

I am seeking some experience with the following issue I have.

My setup is on a Boxford AUD 4.5" lathe (similar to under driven Southbend)

The motor is a TECO 0.75Khz (1HP) 3 phase, 4 pole 230v AC driven unit

https://docs.rs-online.com/7405/0900766b8120451f.pdf

fed by a 230v AC supply via a Chinese TECO E2 VFD

(https://elektromotor-online.nl/wp-content/uploads/2016/10/E2_ManualEnglishV11.pdf)

equipped with remote Fwd/Stop/Reverse switch with single turn 0-10v resistance Potentiometer (POT).

The lathe has been running perfectly until about a year ago when I noticed a decrease in the torque of the lathe, when working on pieces I would notice the spindle slowing down on cutting.

I haven't needed to use the lathe for about a year and it has been stored under cover in my outdoor workshop. I went to use it a couple of days ago and gave everything a spring clean and checked power etc and switched on.

The lathe ran in both forwards and reverse although I noticed that a couple of times I had to nudge the chuck to get it to run forwards. I also noticed that the POT would cut out part-way through the full range. I remove the POT cover and tested the POT and found that it had a defective central terminal (flexing and losing contact) but, could get it to respond across the full range if the terminal was pressed. I have replaced the POT with a new one of the same rating and tested the new POT and it works normally.

However, on switching on the lathe, only the reverse works and still with poor torque.

I have checked the frequency rise on the VFD LED display during POT adjustment and it records the Hz changing as expected between 0 and 50hz as programmed when switched in both directions on the remote.

I have checked the output voltage of all three output terminals from the VFD whilst switched on to max 50Hz running and am getting inconsistent values across all three terminals. Some report 230v some 140v and 160v. These voltages vary between the terminals.

Should I get steady 230v reading at each terminal and see a corresponding voltage decrease as the POT is turned down?

My suspicions are that the VFD has bitten the dust

Sorry if this is a bit of a long-winded post but would like to try and narrow this down a bit further before committing money out on the wrong parts for repair.

Thanks for reading

George

Reset the drive and then carefully program whatever parameters you did before. Then run a auto-tune function.

It's possible that the machine motor is not able to keep up with the demands placed on it.

I have managed to cure the problem with a new Bosch Roxeth 2.2kw VFD. However, like a lot of things this now shows the weakness of the ageing motor...

Couple things you might check.
Voltages on your legs.
Put a scope on the output and look at the wave forms. Do this only if you are a comfortable with using a scope where High voltage and current are present. Use a differential probe cause the ground on most scopes is directly connected the chassis. If you don't use this you stand a good chance of blowing up the scope's front end and yourself. Also make sure to discharge all caps or let it sit for 10 min; those caps hold a wallop.
VFD as you know are PWM (Changes Frequency NOT voltage.) you may have a bad FET or leaky capacitor.
That being said smaller VFDs are cheap, might be worth just obtaining a new one.
I only test and repair VFDs that cost over a grand.

George Cooper said:

I have managed to cure the problem with a new Bosch Roxeth 2.2kw VFD. However, like a lot of things this now shows the weakness of the ageing motor...

Click to expand...

I understand the comment as:

A brand new Bosch VFD cures the problem. But after the "However" part:

This shows the weakness of a ageing motor with the old VFD?
or
This shows the weakness of a ageing motor with the new VFD. The cure is not 100%?