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Author Topic: VFD and motor voltages  (Read 16157 times)

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Offline Katoh

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VFD and motor voltages
« on: June 15, 2011, 10:42:22 AM »
Colleges
Just getting parts together to do a conversion on a lathe.
Looking at a VFD at present with a 2hp capability should work really well on a 1hp motor. Now I'm getting a bit confused on the subject of voltages and outputs , and the manufactures have got back to me saying I'm right but there talking about things that dont even apply to the motor ratings I'm looking at.
Question.
If your supply to the VFD is Single phase 240v input, the output will be 240v 3phase. So do we look for a 3 phase 240v US style motor or a 415v 3Phase Aus/UK motor? Remember this is just VFD not a step up or down transformer.
Delta to star connections and starters really should have nothing to do with this, they dont come into play till we look at 10kw plus motors, starting under load.
Thanks
Katoh
Cheers
Katoh

Offline BR549

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Re: VFD and motor voltages
« Reply #1 on: June 15, 2011, 11:01:35 AM »
The motor HAS to match the supplied voltage (;-)

Just a thought (;-) TP

Offline BR549

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Re: VFD and motor voltages
« Reply #2 on: June 15, 2011, 11:02:11 AM »
The motor HAS to match the supplied voltage (;-)  +/- 5%

Just a thought (;-) TP

Offline Katoh

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Re: VFD and motor voltages
« Reply #3 on: June 15, 2011, 11:12:51 AM »
Ok thats true, but are we looking at the output as 240v a phase or combined, this is were I am getting lost.
 If its per phase than 415? or 240v input = 240v motor?
Cheers
Katoh

Offline Hood

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Re: VFD and motor voltages
« Reply #4 on: June 15, 2011, 11:31:29 AM »
Often 415 motors can be connected  Delta and that will make it 240v

Hood

Offline Katoh

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Re: VFD and motor voltages
« Reply #5 on: June 15, 2011, 11:39:40 AM »
Hood
Yes delta and star connections change things around, 240 to 415, I dont know if one looses rpm while the the other looses torque?
If we get out of the VFD 240v /phase isn't that the same then as mains 3 phase?
Cheers
Katoh

Offline Tweakie.CNC

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Re: VFD and motor voltages
« Reply #6 on: June 15, 2011, 11:53:36 AM »
Katoh,

Mains 3 phase is 415v between each phase wire. (In turn each phase wire is 240v to Neutral).

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Katoh

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Re: VFD and motor voltages
« Reply #7 on: June 15, 2011, 12:00:54 PM »
So if single 240v input into the VFD and we have 240 per phase output, we effectively have a 415 supply?
Cheers
Katoh

Offline Hood

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Re: VFD and motor voltages
« Reply #8 on: June 15, 2011, 12:03:00 PM »
A VFD which can be connected 240v single phase on the input will be 240v 3 phase output I think.

Hood

Offline Katoh

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Re: VFD and motor voltages
« Reply #9 on: June 15, 2011, 12:09:22 PM »
If what your saying is correct then each phase outputting the VFD will be 110v to make a 240v 3Phase supply.
Cheers
Katoh