Motor star to delta

[TheBrick]

I am installing a lathe and I am using an inverter to power the three pages motor from a single phase supply.

I made the silly assumption that I could easily rewire the motor to delta as all the motors I had encountered when I worked in control systems had link bars. Oh how silly I was.

Anyway I think I have found the connection point in the end of the stator. My plan is to dig this out and run some wires to be able to rewire as delta.

My question is to dig it the connection I need to carefully cut some of the string holding everything together. How should I tie everything back up? What string? Or should I not worry as the varnish keeps everything in place?

Pic to give some idea. I need to go digging but pretty sure the star point is in bundle near the bud ~ 1 o'clock.

 

[slimjim]

I just did this with my rapidor hacksaw motor,
You don’t have to tie back up, I used some of that clear hybrid glue sealant to stick it back down, so it was neat and tidy, because I used it on a job earlier that day and it was spare

 

[6ply]

I used high temperature cable ties and sprayed the windings with conformal coating. Was rock solid.

 

[Smouser]

I used high temperature sleeving to tie up the motors I have done before.

Something like this.

*Edit*
Here is a photo of one of the motors.

 

[Agroshield]

What string?

Whatever string a butcher uses to truss up your joint of meat. If it survives 180 dungarees in an oven, it will survive in a motor.

https://www.sainsburys.co.uk/gol-ui/product/kitchencraft-cooking-string

 

[6ply]

I used high temperature sleeving to tie up the motors I have done before.

Something like this.

View attachment 487330

*Edit*
Here is a photo of one of the motors.

View attachment 487331

Snap...

 

[Pete.]

The propwr stuff is some kind of waxed flat cord but I've used all sorts of stuff. Anything even slightly abrasive risks removing the thin costing on the winding wire and causing an electrical short but if you are careful you could use ordinary string and give it a coat of winding varnish.

You do need to secure those wires. The AC current causes friction between any touching parts which is why they are all encasulated/varnished. A tin of the stuff from Brocott doesn't cost the earth.

 

[minimutly]

Shellac was the stuff back in the day...

 

[TheBrick]

Brilliant information guys! Thanks. I think I have some high temp sleeving just need the varnish.


Didn't feel right not securing it as we all know that AC buzz plus and mechanical vibration will at some point cause an issue.

A tin of the stuff from Brocott doesn't cost the earth.

Never heard of them but what a useful supplier thanks.

 

[6ply]

The propwr stuff is some kind of waxed flat cord but I've used all sorts of stuff. Anything even slightly abrasive risks removing the thin costing on the winding wire and causing an electrical short but if you are careful you could use ordinary string and give it a coat of winding varnish.

You do need to secure those wires. The AC current causes friction between any touching parts which is why they are all encasulated/varnished. A tin of the stuff from Brocott doesn't cost the earth.

Good suggestion, @Pete.

Electrical Insulation Materials

A range of Air drying varnish, fibre glass tapes, adhesive fibre glass tapes, nomex insulation sheet

brocott.co.uk

 

[Guineafowl]

Proper stuff is called stator lacing cord, but as above I use butcher’s string.

A good lacing pattern, if you’re medically inclined, is Ford interlocking, aka blanket stitch.

 

[Smouser]

I have decided to go for the eBay option from Brocott.

£17.45 including delivery for 500ml (highly unlikely that I will ever use the whole 500ml).

Black

Pardon our interruption...

Clear

Pardon our interruption...

 

[TheBrick]

That's good I could only find the 1ltr version for £24.something. It will be another mystery tin of stuff that my kids throw out when I die so may as well get the smaller tin.

 

[Pete.]

That winding varnish will go off in the tin if there's the lightest bit of air can get to it.

 

[6ply]

That winding varnish will go off in the tin if there's the lightest bit of air can get to it.

Whereas spray conformal coating stays good indefinitely. I've found it works fine on motor windings.

 

[TheBrick]

Two good but of info thanks. I haven't done the order yet so still time to edit basket

 

[Agroshield]

Whereas spray conformal coating stays good indefinitely. I've found it works fine on motor windings.

Data sheet attached. If we look at the temperature numbers given thereon and then look at motor temperature classes:

https://www.toshiba.com/tic/datafiles/app_notes/Temperature_Rise_1605749858.pdf

there seems to be a slight mismatch.

 

[6ply]

Good call, but...



The older motors that I tend to work on whenever I convert from star to Delta barely get warm. Buy way of contrast, the cheap low duty cycle motors that tend to get shipped with the Chinese equipment would be good to cook eggs.

 

[daleyd]

Good call, but...



The older motors that I tend to work on whenever I convert from star to Delta barely get warm. Buy way of contrast, the cheap low duty cycle motors that tend to get shipped with the Chinese equipment would be good to cook eggs.

Also in a home workshop intermittent running and long periods stopped would be the norm, unlike for example a pump which could be running for hours/days on end at or near their rated duty amps.

 

[TheBrick]

What's special about the varnish compared to say oil based varnish used on wood? Is it pretty much just temp resistance?