Am I mad

**simonl** · 8th February 2014, 09:46 PM

Hi Andre,

Congratulations once again!

So the only motor is the one that drives the grinding spindle?

Looks like you only have the 3 connections in that motor junction box. Have a look at the plate on the motor, it usually tells you if it's star or delta. But for 3 phase it will most likely be star. You can run a 415V star motor from a 240V VFD without any modifications to the motor but it will be down on it's rated power. Someone like Ray or Stuart would be able to tell you by how much, it maybe 66% but not sure. Try it, see how you go, or get one of the forum members close to you to come over and give you a hand. If VFD is definitely your only option, then I would re-wire the motor and bring all 6 wires out into the junction box, then you can set it up for delta for VFD but still retain the option to change back to star at your will.

Cheers,

Simon

**welder** · 8th February 2014, 10:30 PM

Yes there are only 3 wires coming out of the motor. The vfd will arrive next week so I will it a go next week, if worst comes to worst a single phase motor is $450

**RayG** · 8th February 2014, 10:56 PM

Hi Andre,

Don't bother with a single phase motor on a surface grinder, the three phase motor you already have is much better, 3 phase is much smoother than single phase, and smoother is much better when it comes to surface grinders.

Take the motor to a motor rewinder and ask them to bring out the star point, it's a trivial job for them. Then you can hook it up in delta and get full power on 240V 3 phase.

Ray

**welder** · 17th February 2014, 11:40 PM

Can I use the motor with a VFD at all with the the current 415 volt star wound motor. Or will I let the smoke out of things if I dont get the star point extracted to run duel voltage. I hope this makes sense ??

**RayG** · 17th February 2014, 11:48 PM

Originally Posted by welder

Can I use the motor with a VFD at all with the the current 415 volt star wound motor. Or will I let the smoke out of things if I dont get the star point extracted to run duel voltage. I hope this makes sense ??

Hi Andre,

Funny, I just answered this very question in the other thread. No you won't damage anything, the wheel speed will still be the same, but you'll have a lot less power. Maybe less than 1/3 of what you would have got on 415V

Ray

**welder** · 17th February 2014, 11:52 PM

cheers Ray I havent even looked at the other VFD thread

I will give it a try and see how it goes If its terrible I will take it apart and take it to the motor shop

**welder** · 25th February 2014, 12:31 PM

it will be $400 to reword te motor

**Stustoys** · 25th February 2014, 12:54 PM

Hi Andre,

Did they see the motor or did you ring them?
Did you ask for a price to have it rewound?
Or did explain you wanted to run it on a VSD and needed it rewired for 240V?

Stuart

**welder** · 25th February 2014, 02:18 PM

Originally Posted by Stustoys

Hi Andre,

Did they see the motor or did you ring them?
Did you ask for a price to have it rewound?
Or did explain you wanted to run it on a VSD and needed it rewired for 240V?

Stuart

I rang one guy Austin electric he said it would be $400 and the motor is siting in another shop who looked at it and quoted $400

**Stustoys** · 25th February 2014, 02:35 PM

To me that sounds like a lot. Though I've never had a quote to have it done. Last time I got a quote to have a motor rewound was for a 3/4hp single phase motor, it was about $400*(so not worth it, bought a new motor). Now rewinding is a lot more work than rewiring...... but then maybe I am missing something. Be interesting to see what others have to say.

Stuart

*maybe I'm just that old lol

**welder** · 25th February 2014, 02:53 PM

I don't have much of an idea but $400 is the same as a single phase motor which whilst not ideal for a ginder is the option I would settle on. The motor guy seem to say it needs rewinding an can't be rewired

**Stustoys** · 25th February 2014, 03:19 PM

Originally Posted by welder

The motor guy seem to say it needs rewinding an can't be rewired

Well one would hope he knows more than me

You did explain you wanted to run it on a 240V VSD? (you didnt just say "240V" and maybe he assumed single phase?)

Stuart

**welder** · 25th February 2014, 03:24 PM

I said I wanted 6 wires in the terminal box to run it on 240v 3 phase

**Ueee** · 25th February 2014, 03:34 PM

I'll pull the star point out for you for $350....

Seriously if you want to make the trip i'll show you how to find it and bring the wires out. $400 is crazy if its just bringing the point out, you may as well buy a new motor with it already done.....

Ew

Wow you guys type fast oops actaually i think i missed reading posts from #40 on...If you want to i can have a look anyway.....

**Stustoys** · 25th February 2014, 03:46 PM

Originally Posted by Ueee

Wow you guys type fast oops

you take that back

lol

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