[Al_The_Man]

A resistance measurement on an AC motor is not a really conclusive test.
As I mentioned before, I would test it on true three phase and put a load on it and then measure the current with a clamp on meter for a conclusive test.
Al.

[Deano7/11]

motor is off the mill and will be dropped off at rewinders today for testing.

hopefully have an answer by the end of this week start of next.

[Deano7/11]

well the plot thickens.

i just got back from the rewinders and he pulled my motor apart and tested it.

guess what ---- it tests out perfect. we had it running on 220v 3 phase and when you turn it on while holding the motor on the bench there was a 'kick' when starting as the motor wanted to spin around its rotor.

the rewinder said the rotor was good. it tested up fine.

the only thing it can be now is that the vacon invertor is not compatible with the motor.

so frustrating

[Algirdas]

vacon invertor is not compatible with the motor
this is very interesting. Is there some intelect inside a motor, which cannot communicate with output of inverter?
Let's start from the beginning. You see, the motors are different. Resistance of windings is different even with DC test. Is that right? You see, the motor rewinded is very good - healthy and powerfull. So, what's the problem now? Motors are different and that's it. Both works perfect. You just need to adjust properly.

[Deano7/11]

i think i found the problem.

and guess what

it was not the invertor or the motor.

you will laugh at this one.

after getting the motor tested i went home and had a good think about what was going on. i returned to basics would you say. i connected the motor up to he invertor and electrics of the lathe and ran it on the floor. i got a welding glove and shoved my hand in the between the cone pullies to load the motor up. it pulled 6 amps. all looking good at this stage.
then i installed the motor back on the mill.
i pulled the covers off the side of the head so i could look in and see what the pullies were doing when i turned the motor on and played with the variable speed dial.

i started the motor again off the lathe invertor and electrics and wound the handle and once again the motor only pulled 3amps and as the rpm of the dial increased the rpm was decreasing. - you can see where this is heading cant you.

i then pulled the fan cover off the motor so i could gauge just how much the motor was slowing down. when winding the speed up the rpm were dropping like made until i could just about count the rpm of the spindle when the dial indicated 4200rpm. i then stood on a chair to check out the fan speed and what do you no the motor is still flying around at what looks like full speed.

by this stage i was in shock . i had this awful thourght that i had gone through all this stuffing around all because someone had pulled apart the variable speed dial and put it together back to front so when you wound on more rpm the dial showed the rpm increasing but infact it was actually going the wrong way.

i had a little look behind the adjuster and noticed hte piece of chain that wrapped around the shaft was wrapping to the right so i pulled it apart adn changed it to wrap to the left put it together and what do you no as you wind the handle the speed goes up matching the speed indicator.

so after all that there was never a problem with the motor or the invertor the problem was that i was watching the speed indicator dial increase in rpm but hearing and seeing the spindle drop in rpm after just having a quick look at what was going on came to the conclusion that the motor was causing hte problem. if i had have taken a little more time to look further i probably would have found it but hey it now works. now i can start making swarf.

thanks to all that assisted with my problem sorry to send you on a wild goose chase.

[mactec54]

Deano7/11

I'm glad you got it all sorted out, you never did mentioned anything about your machine drive, most make them 1/1 when using a VFD, but if it is in good shape then there is no need to do that

[Deano7/11]

the cone pullies look to be in great condition so thourght i would just leave them as is until i have a need to change to a 1 to 1 drive. i have heard people do the 1 to 1 drive when using a vfd also

[RCaffin]

Mirth.
Murphy!

Swarf on.