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Author Topic: VFD and motor voltages  (Read 16311 times)

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Offline Tweakie.CNC

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Re: VFD and motor voltages
« Reply #10 on: June 15, 2011, 12:09:41 PM »
I agree with Hood  240V ;)

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

Offline Tweakie.CNC

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Re: VFD and motor voltages
« Reply #11 on: June 15, 2011, 12:11:46 PM »
Where do you get 110v from ?

There are only 3 outputs and it is 240v between each output making the output 240v, 3 phase.

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

Offline BR549

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Re: VFD and motor voltages
« Reply #12 on: June 15, 2011, 12:18:40 PM »
The output will be 240v 3 phase delta. With 240V between any two legs.  It can't be Y because there is NO neutral.

(;-) TP

Offline Katoh

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Re: VFD and motor voltages
« Reply #13 on: June 15, 2011, 12:24:06 PM »
If on the mains you meter from active to neutral you should have 240v/ phase. If you have a 3phase 240v  US style power and you meter between an active and neutral you should have 110v. Theres may reasoning.
I'm looking at this from the motors side. with a 3phase motor (415v) each phase entering the motor is carrying 240v, and that's what should be coming  out of the vfd on each phase.
I think.
Cheers
Katoh

Offline BR549

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Re: VFD and motor voltages
« Reply #14 on: June 15, 2011, 12:34:52 PM »
US power 3 phase Y, phase to Ground 120v Phase to phase 208v  , 3 TX bank

240v 3 phase delta with high leg.  A to N 120v   B to N 120v   C to N 240v    240v phase to phase , 2 TX bank

240v  open delta  240v phase to phase no neutral , 3 TX bank


BUT all that is irrelevant as you have 240v 3ohase output and NEED a 240v 3p motor (;-)

(;-) TP
« Last Edit: June 15, 2011, 12:39:41 PM by BR549 »

Offline Tweakie.CNC

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Re: VFD and motor voltages
« Reply #15 on: June 15, 2011, 12:39:30 PM »
Best you read your VFD manual and "How to connect a motor" - if you experiment, as you suggest, you could loose both your motor and your VFD.

Henk explains dual voltage motors here http://www.scribd.com/doc/22398221/Star-Delta-Starting-and-Dual-Voltage-Motors-Explained

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: VFD and motor voltages
« Reply #16 on: June 15, 2011, 01:44:06 PM »
It sounds  like so far this assumes that the 3 phase has the same characteristics as mains provided 3 phase.
A VFD has to control frequency and MEAN voltage and current and usually does this through PWM signal that is sine wave in shape, if it did not, the 3 phase rectifier and capacitor bank on the input of a 220v VFD would provide constant sine wave of >300v amplitude due to the level of the DC.
In any case, all the VFD's I have used have a parameter setting for motor voltage, within the VFD range that is.
Also because it is electronically  produced, there is no Star or Delta, just three phases spaced 120deg apart with ~220v between phases.
N.


« Last Edit: June 15, 2011, 01:54:54 PM by NosmoKing »

Offline Hood

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Re: VFD and motor voltages
« Reply #17 on: June 15, 2011, 03:10:19 PM »
I dont have a lot of experience with VFDs and even less with single phase input ones. Having said that I have never seen a VFD that outputs a higher voltage than the input voltage and for the single phase 240v input ones I have never seen one capable of outputting more than 240v three phase. As said my experience with VFDs is limited so take of it what you will.

Hood
Re: VFD and motor voltages
« Reply #18 on: June 15, 2011, 03:28:57 PM »
Having said that I have never seen a VFD that outputs a higher voltage than the input voltage and for the single phase 240v input ones I have never seen one capable of outputting more than 240v three phase.

What of the 120v 1 ph input models that run a 240v 3ph motor?
http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_%28120_-z-_230_VAC_V-z-Hz_Control%29
Agreed they are in the lower HP range.
You may not run across them in the UK due to no 120vac generally.
N.

Offline Hood

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Re: VFD and motor voltages
« Reply #19 on: June 15, 2011, 03:35:39 PM »
Nope never seen them here, only 110v we normally have here is on sites for power tools.
So are there 240V single phase input VFDs that will output 415V three phase? I have never seen one but again my experience with VFDs is limited.
Hood