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  #1  
Old Tue 28 July 2009, 20:35
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
3 phase vs single phase VFD's - is there a loss in one vs the other?

all of you who have spindles out there I was wondering if there is loss when running a say 5 hp spindle with a single phase vfd, I have been researching this and have not found a definitive answer, I have heard it both ways that there is a loss of power with a single phase vfd, but not with a 3 phase, could some one who knows please explain this for me, thank you //chopper
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  #2  
Old Tue 28 July 2009, 21:57
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The way I understand it is that many 3ph VFD's can be powered from 1ph, but that the power output of the VFD then drops. Thus one must buy an oversized 3ph VFD if you are going to run it on 1ph. If you shop correctly for the VFD, there needs to be no loss of power at the spindle.
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  #3  
Old Wed 29 July 2009, 08:49
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
the vfds I am looking at are made to run on single phase so there should be no issue then,...
thanks for the info Gerald..
thanks//chopper
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  #4  
Old Wed 29 July 2009, 12:11
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
You must get the manufacturer of the VFD to guarantee a power output level when run on single phase. They will tell that their VFD's can be used on single phase, but they don't generally tell you that the power output will be reduced.
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  #5  
Old Thu 30 July 2009, 08:40
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
If you can get the spec sheet for the VFD compare its output capabilities when run on 3PH input vs 1PH input. IUf they are not the same, then you might have to resize / rethink the vfd / spindle combo to get the needed output as Gerald suggests.
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  #6  
Old Thu 30 July 2009, 09:12
jeffa
Just call me: Jeff
 
Iowa
United States of America
Just FYI, when talking to PDS about purchasing a VFD to run the 5 HP spindle that I purchased. They recommended a 10 HP VFD to run the 5 HP spindle with a single phase input rather than a three phase input. The output from the VFD to the spindle motor will, of coarse, continue to be three phase.

Jeff
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  #7  
Old Fri 31 July 2009, 02:07
Corwes
Just call me: Corwes
 
Stouffville ,ON
Canada
It all comes down to the input bridge rectifier. When you run the VFD in three
phase the current is shared across 6 diodes ( and they were sized with this in mind). When you run it in single phase the current is shared across 4 diodes , so you only need to derate your VFD by 2/3 rds. Or you can just use a larger bridge rectifier and connect it directly to the DC bus then you do not need a larger and more expensive VFD.
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  #8  
Old Fri 31 July 2009, 03:12
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Corwes View Post
. .so you only need to derate your VFD by 2/3 rds. .
In other words, when a VFD is run on single phase, it can typically only handle 2/3 rds of the 3-phase rating, before it overheats. However, Some VFD manaufacturers may have oversized the diodes to start with.

And then I wonder how the VFD's detect that they are being overloaded before they give a warning or shut down . . .
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  #9  
Old Fri 31 July 2009, 08:26
jeffa
Just call me: Jeff
 
Iowa
United States of America
Gerald,

I do believe a number of VFDs do have over current protection built in. As well most three phase VFDs have protection for a phase loss. It is important to obtain a drive that will allow this protection feature to be disabled or reconfigured if you plan to use a single phase input scheme.

Jeff
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  #10  
Old Fri 31 July 2009, 10:39
Corwes
Just call me: Corwes
 
Stouffville ,ON
Canada
The majority of the over current protection features apply to the output .
Unfortuanately the manufacturers optimize everything so seldom will you
find over sized components just on the one side.
I have run Allen Bradley , SEW Eurodrive and Siemens 3 phase inverters
of single phase without any problems.

The fear of running a 3 phase inverter of single phase is what makes
the single phase ones much more expensive on E-bay( more people bidding).
I am not complaining.

Totally OT: you can control the speed of the majority of your ,single phase AC induction motor, shop equipment (band saw, disk sander , dust extractor etc.)from a 3 phase output inverter (single phase output inverters are rare and expensive)
Just disconnect the running capacitor , follow the wires and you will notice it is in fact a 3 phase motor. It is a bit more complicated if the motor has 2 capacitors ( starting and running cap) but not impossible.
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  #11  
Old Tue 01 February 2011, 14:01
alan254
Just call me: Al #95
 
mystic ct
United States of America
3ph vfd on 1ph

hi all,

attched is a series of e-mails between myself and ac tech on running their 3ph vfr on 1ph.

thanks
al drouin
Attached Files
File Type: doc vfd.doc (22.0 KB, 110 views)
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  #12  
Old Fri 24 June 2011, 19:06
r0bs
Just call me: r0bs
 
Brisbane (Queensland)
Australia
Send a message via Skype™ to r0bs
Gents, the loss of power is to do with the voltage drop. I'll use the Australian 240v grid as an example.

A single-phase VFD takes the 240 v AC and converts it to 240 v DC. It then chops this into a poly-phase (three-phase) supply at whatever frequency (Hz) has been selected on the VFD, however whilst you can change the frequency, you cannot change the voltage between phases. The maximum voltage between phases on a 240v single-phase VFD will be 240v. (as the input is only 240v which is obtained between a single-phase and neutral)

If you use a poly-phase VFD (i.e.: three phases with 415 v between phases) then the output between phases remains the same ( 415 v between phases)
This allows more "power" for the same current.

It should be noted that a poly-phase VFD internally is really similar to a bank of three (3) single-phase inverters, but they are running on the line-to-line voltage of 415v rather than the line-to-neutral voltage of a single-phase inverter.

For the same current input you will get approx 2.7 times as much grunt out of the poly-phase VFD.

Hope this helps.
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  #13  
Old Sat 25 June 2011, 07:26
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
R0bs-

I think this issue is regional, or at least depends on the step down transformers used in the area. In the U.S. the "normal" single phase service comes in with two hot legs and a neutral. It has 120v between one leg and the neutral, and 240v between the hot legs; it comes from a center tapped transformer the power company provisions. Normally, we run a VFD on 240v for single phase when in this environment.

In the areas where 120v/240v service is common (residential, small commercial), when 3 phase power is available, it is 120v/208v, with 120v between leg and neutral, and 208v leg to leg. So the single phase service is actually at a higher voltage than the three phase service.

There is another class of 3 phase service that is common in industrial areas. This is 277v/480v service.

So in this common U.S. case, the "loss of power" is due to the limitations of the input rectifiers in the VFD, as you are only utilizing two of them rather than three. In some cases, this requires purchasing an "over-sized" VFD to get adequate amperage capacity in the input phase.
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  #14  
Old Sat 25 June 2011, 07:47
nisma
Just call me: chris
 
bz
Italy
Itīs really the diodes or the capacitors. Diodes are cheap. I suppose the problem is the voltage drop because of the ripple and power loss during the 120hz blanks supplied from
capacitator. Higher powered VFD means automatically higher caps and as such higher
voltage and more power reservoir during power blanks.
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  #15  
Old Sun 07 April 2013, 05:56
Hardouin
Just call me: Hardouin
 
Douarnenez
France
Hello !

I am looking for a VFD for my spindle and I am would like to know what does "HP" means.

Thank you !
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  #16  
Old Sun 07 April 2013, 07:26
xraydude
Just call me: Ted
 
New Orleans, LA
United States of America
Horse Power. 1 hp = 746 watts. (Metric hp = 735 watts) So, a typical 3hp spindle would be about 2200 watts or more commonly referred to as 2.2 kw.

Ted
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  #17  
Old Mon 08 April 2013, 03:38
Hardouin
Just call me: Hardouin
 
Douarnenez
France
Thank you Ted !
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