UK 480v Split Phase, new workshop, VFD's required

[robertl]

Hi All,
I've posted on here before about this, that time i was asking what people thought about phase converters as at that point i thought i could only get a single phase line at 100a for my new workshop.
Turns out that after the DNO visited the site i can get a Split Phase connection put in and give myself the cushion of 2x100A supplies at 240v or obviously 480v phase to phase.
So i have specced all my equipment i will be using and getting for the workshop, i have several welders and they are all single phase and plenty beefy for what i need. all machine tools i can get in single phase or small enough motors i could either fit a small VFD or change the motor out for a single phase one
The large hydraulic equipment is where i am going to fall down, the motors will be in the range of 5 to 7.5kw and i'm not sure how to power them if i'm honest. I was thinking the VFD route to get the soft start function but 240v VFD's dont seem to be a thing at that size as far as i can tell, what about the 480v phase to phase of the split phase system i will have, could this be used to power the vfd?
The other options i have been looking at have been either a RPC or a Digital Phase Converter from Drives Direct, what has since put me off them has been the cost, for a 20hp whole shop one it was going to be 8K and it just seems a bit much to me.
Before anyone asks i cant get 3 phase at the moment, its just too costly to get, the best estimate is another 18k plus vat on top of what i'm already paying for single or split phase so at least for the moment and until the business gets going i will be sticking with the split phase supply with either motor changes or VFD's, whichever is cheapest.
Any help on the above will be greatly appreciated
Thanks

 

[FarmersFriend]

Hi All,
I've posted on here before about this, that time i was asking what people thought about phase converters as at that point i thought i could only get a single phase line at 100a for my new workshop.
Turns out that after the DNO visited the site i can get a Split Phase connection put in and give myself the cushion of 2x100A supplies at 240v or obviously 480v phase to phase.
So i have specced all my equipment i will be using and getting for the workshop, i have several welders and they are all single phase and plenty beefy for what i need. all machine tools i can get in single phase or small enough motors i could either fit a small VFD or change the motor out for a single phase one
The large hydraulic equipment is where i am going to fall down, the motors will be in the range of 5 to 7.5kw and i'm not sure how to power them if i'm honest. I was thinking the VFD route to get the soft start function but 240v VFD's dont seem to be a thing at that size as far as i can tell, what about the 480v phase to phase of the split phase system i will have, could this be used to power the vfd?
The other options i have been looking at have been either a RPC or a Digital Phase Converter from Drives Direct, what has since put me off them has been the cost, for a 20hp whole shop one it was going to be 8K and it just seems a bit much to me.
Before anyone asks i cant get 3 phase at the moment, its just too costly to get, the best estimate is another 18k plus vat on top of what i'm already paying for single or split phase so at least for the moment and until the business gets going i will be sticking with the split phase supply with either motor changes or VFD's, whichever is cheapest.
Any help on the above will be greatly appreciated
Thanks

Hi All,
I've posted on here before about this, that time i was asking what people thought about phase converters as at that point i thought i could only get a single phase line at 100a for my new workshop.
Turns out that after the DNO visited the site i can get a Split Phase connection put in and give myself the cushion of 2x100A supplies at 240v or obviously 480v phase to phase.
So i have specced all my equipment i will be using and getting for the workshop, i have several welders and they are all single phase and plenty beefy for what i need. all machine tools i can get in single phase or small enough motors i could either fit a small VFD or change the motor out for a single phase one
The large hydraulic equipment is where i am going to fall down, the motors will be in the range of 5 to 7.5kw and i'm not sure how to power them if i'm honest. I was thinking the VFD route to get the soft start function but 240v VFD's dont seem to be a thing at that size as far as i can tell, what about the 480v phase to phase of the split phase system i will have, could this be used to power the vfd?
The other options i have been looking at have been either a RPC or a Digital Phase Converter from Drives Direct, what has since put me off them has been the cost, for a 20hp whole shop one it was going to be 8K and it just seems a bit much to me.
Before anyone asks i cant get 3 phase at the moment, its just too costly to get, the best estimate is another 18k plus vat on top of what i'm already paying for single or split phase so at least for the moment and until the business gets going i will be sticking with the split phase supply with either motor changes or VFD's, whichever is cheapest.
Any help on the above will be greatly appreciated
Thanks

It may be worth checking out old farm equipment as a source of large single and split phase motors. I work on lots of grain handling installations that only have single phase supplies, one I’m doing at the moment has a 20hp 68a single phase series-parallel motor on the fan!
The old starters which you crank down for start and swiftly move up for run are quite simple to overhaul.
Give me a list of what you need as I never know what I might come across on farms.
I have wiring diagrams for a lot of the old motors and starters.

 

[ipf]

When you say 'split phase' do you mean 3 phase? Sounds like you'll need 3 phase for the machinery motors....and it's 400v between phases.

 

[FarmersFriend]

Another way for the hydraulic drives would be to use engine driven hydraulic pumps
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When you say 'split phase' do you mean 3 phase? Sounds like you'll need 3 phase for the machinery motors....and it's 400v between phases.

Split phase is plus and minus 230v (3 wire) plus neutral, it is used where you only have single phase HV

 

[robertl]

When you say 'split phase' do you mean 3 phase? Sounds like you'll need 3 phase for the machinery motors....and it's 400v between phases.

No its L1 Neutral L2 as far as I understand its 2x 240v legs 180 degrees apart. So 240v phase to neutral and 480 between L1 and L2
[automerge]1571251892[/automerge]

Another way for the hydraulic drives would be to use engine driven hydraulic pumps
[automerge]1571251624[/automerge]

[automerge]1571251792[/automerge]

Split phase is plus and minus 230v (3 wire) plus neutral, it is used where you only have single phase HV

Hlengine driven pumps would work yes but would rather have a way of supplying these from the mains if possible

 

[Lucien Nunes]

Split-phase = single-phase with centre tap, 230-0-230. Older, rural supplies use it where there is no 3-phase HV available, to reduce currents. Large loads like motors run on the outers (460V) while normal domestic loads run L-N (230V)

It is possible to operate some 3-phase input VFDs on single-phase supplies in these power ranges. Possibly 230V input with the motor wired for 230, possibly 460V with the motor wired for 400 and limited in the VFD or by bucking transformer. You may have to source from the USA to get the right configuration.

There are limitations:

• The VFD must be derated by as much as 50%, to avoid overloading the bridge rectifier (as only two input lines are used to handle the full power, not three) and to minimise reservoir capacitor heating (as the ripple is much greater on 1-phase than 3-phase). I.e. you might be forking out for a 15kW VFD for your 7.5kW motor.
• Some manufacturers sanction this use and offfer recommended derating factors. Others do not sanction it and it will invalidate the warranty.
• An additional DC bus choke may be needed
• Some VFDs may not allow their phase loss detection to be deselected, in which case they will not work because the lack of one phase locks them out. It is possible to 'spoof' some of those to think the 3rd line is present.

I am not saying this is the best way to proceed, merely that I think it is possible.

 

[ipf]

No its L1 Neutral L2 as far as I understand its 2x 240v legs 180 degrees apart. So 240v phase to neutral and 480 between L1 and L2
[automerge]1571251892[/automerge]

Hlengine driven pumps would work yes but would rather have a way of supplying these from the mains if possible

Fair enough, I'm with you now. Sounds like it's gonna be costly, though.

 

[robertl]

Split-phase = single-phase with centre tap, 230-0-230. Older, rural supplies use it where there is no 3-phase HV available, to reduce currents. Large loads like motors run on the outers (460V) while normal domestic loads run L-N (230V)

It is possible to operate some 3-phase input VFDs on single-phase supplies in these power ranges. Possibly 230V input with the motor wired for 230, possibly 460V with the motor wired for 400 and limited in the VFD or by bucking transformer. You may have to source from the USA to get the right configuration.

There are limitations:

• The drive must be derated by as much as 50%, to avoid overloading the bridge rectifier (as only two input lines are used to handle the full power, not three) and to minimise reservoir capacitor heating (as the ripple is much greater on 1-phase than 3-phase).
• Some manufacturers sanction this use and offfer recommended derating factors. Others do not sanction it and it will invalidate the warranty.
• An additional DC bus choke may be needed
• Some VFDs may not allow their phase loss detection to be deselected, in which case they will not work because the lack of one phase locks them out. It is possible to 'spoof' some of those to think the 3rd line is present.

I am not saying this is the best way to proceed, merely that I think it is possible.

Thanks for your answer
So if this isn't the best way to proceed, what would you say is?

 

[Lucien Nunes]

No one solution comes to mind as best, I was just adding the 3-phase VFD option to the mix.

 

[robertl]

No one solution comes to mind as best, I was just adding the 3-phase VFD option to the mix.

I've been having a look at using the 460v in to the Vfd and the one I looked at is saying it needs de rated by 1/3, it also says it can reduce the output voltage by 10 percent so that seems like quite a good fit.
I guess for the 460v connection it will be basically a live from each side. A neutral plus earth. It's maybe a good idea to fit a separate 3 phase board for the 460 stuff.

 

[Lucien Nunes]

a live from each side. A neutral plus earth

No neutral - the two lines of the split-phase supply are a 460V single-phase supply as far as the VFD is concerned. Obviously they must both be fused and switched as lines, rather than a line and a neutral.

 

[robertl]

No neutral - the two lines of the split-phase supply are a 460V single-phase supply as far as the VFD is concerned. Obviously they must both be fused and switched as lines, rather than a line and a neutral.

Understood, can probably just take a line from each 240v consumer unit then. Don't you need a neutral with these vfds then?

 

[Lucien Nunes]

can probably just take a line from each 240v consumer unit then

Nope, that could backfeed one CU from the other when switched off, a very dangerous situation. Any switches / MCBs anywhere on the 460V circuit from suppliers' meter to VFD must be linked double pole devices. IIRC not all 3-phase boards are officially rated for 460V, worth checking.

 

[robertl]

Nope, that could backfeed one CU from the other when switched off, a very dangerous situation. Any switches / MCBs anywhere on the 460V circuit from suppliers' meter to VFD must be linked double pole devices. IIRC not all 3-phase boards are officially rated for 460V, worth checking.

Maybe a stand alone double pole switch mounted in an enclosure would be the way to go, what about the neutral though? Not required?

 

[Lucien Nunes]

Not for the VFD power itself. If the machine had any auxiliary devices, lights etc. they might need the neutral (or need feeding separately from a 230V circuit).