VFD on 230V 50Hz single-phase power source to drive 400V 50Hz three-phase IM load 2

[che12345]

Dear Sir,
Utility power source: 230V 50Hz single-phase. Load is a centrifugal water pump IM rated 400V 50Hz 11kW 22A three-phase. Wish to regulate the pump speed by using a VFD.
The problems are:
a) a VFD rated for 230V single-phase input is unable to produce 400V three-phase output,
b) unable to source a VFD rated for 400V 50Hz single-phase input,
c) the IM is 400V 50Hz three-phase existing at site. No intention to replace it.
Please advise possible solution.
Che Kuan Yau (Singapore)

 

[itsmoked]

Hi Che,

Put the appropriate transformer between them.
Make sure the VFD is set to simple V/Hz mode.
Set any parameters appropriately that would be affected by the transformer ratio.

Of course you should do the math to make sure the drive can supply the needed current thru the transformation.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[che12345]

Hi Mr. itsmoked (Electrical)15 Jul 22 03:13
"...Put the appropriate transformer between them. Make sure the VFD is set to simple V/Hz mode..."
Thank you for your prompt and learned advice. I take it that you mean:
1) to insert a 230/400 V Yy0 or a Dd0 three-phase step-up transformer between the VFD and the motor?
1.1) this 3-phase step-up transformer should be placed close to the VFD output or at close to the motor? At present, the distance between the VFD and the motor is <30m.
1.2) do you reckon that a transformer designed for 50Hz would function properly at frequency as low as say 25Hz ?
2) the VFD input would be rated for 230V single-phase utility source ?
Please advise.
Che Kuan Yau (Singapore)

 

[LionelHutz]

Yes to all. Probably delta:wye. You need a transformer that is designed to accept higher voltages so it doesn't saturate when the drive does some low end voltage boosting. Something like capable of operating at 300V:520V. You can operate it at any frequency if you maintain the V/Hz ratio applied.

 

[edison123]

A K-rated step up trafo (K rating due to higher harmonics loss due to VFD) and lower than normal design flux density (due to higher hysteresis loss proportional to frequency and eddy current loss proportional to square of frequency) if you plan to operate above 50 Hz.

As long as V/F does not lead to magnetic flux saturation, the trafo will work fine at any frequency.

Muthu

http://www.edison.co.in

 

[EdStainless]

We used to build motors that ran at odd voltages (2345V, or 3185V, or such) and we did this all of the time.
It does require a very good transformer.
And we limited the rate of change for the speed, depending on the cable length (sometimes up to 14,000').

In your case you could do it the other way around, transformer before the VFD.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[che12345]

@ Dear Mr. EdStainless (Materials)15 Jul 22 15:56
"... We used to build motors that....In your case you could do it the other way around, transformer before the VFD..." .
1. Thanks to all prompt and learned advice.
2. I had considered to have the step-up 230/400V 50Hz single-phase transformer placed ahead of the VFD. This is simple and no complication. The problem is as I had mentioned earlier, VFD rated for 400V single-phase input is not readily available on the market.
3. I am very concerned by placing a 230/400V step-up three-phase transformer in between the VFD output and the motor. This transformer would be subjected to a very wide spectrum of pulse-width-modulation in voltage and frequency, including harmonic and EMC consideration. The insulation voltage level min (say 2kV?), the temperature class (say Class H?) and the k-factor etc., shall be taken into serious consideration. This is evident from manuals stating that attention shall be taken into account on the " length of the cable between the VFD and the motor"..
4. I have no experience on this transformer whether the concern are superfluous; i.e. a normal standard three-phase designed for 50Hz transformer on the market place would be fine.
Your learned advice would be greatly appreciated.
Che Kuan Yau (Singapore)

 

[itsmoked]

You say it's a centrifugal pump. You generally can not turn them down too much as the flow drops quickly with speed. Because of this I expect you won't be tuning it down very far and if you do turn it way down, probably not for long periods. I'd think you won't be stressing the transformer much. Use what you have and monitor it closely until you can assess it's thermal handling of the needed speed/load.

If you have to work hard to come up with a rare transformer it defeats the purpose and you might as well go to the effort of sourcing a right voltage VFD or retrofitting the motor to one capable of 230V.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[che12345]

Dear Mr. itsmoked (Electrical)16 Jul 22 02:19
"....If you have to work hard to come up with a rare transformer it defeats the purpose and you might as well go to the effort of sourcing a right voltage VFD or retrofitting the motor to one capable of 230V....".
1. Thank you for your prompt and learned advice.
2. I consider that this transformer needs careful attention as it is subject to some conditions that is not usually experienced when connect to the net.
3. Input 230V single-phase to run an IM load rated 400V three-phase should be frequently encountered in Europe and in most part of Asia. It is an IEC standard voltage.
To replace or rewind the motor is not an option as this water pump is portable, which would be moved to other sites with standard 230/400V three-phase 50Hz mains.
4. I had posted the same question to VFD manufacturers but yet to receive any advice. Let us wait and see more advice from our friendly and knowledgeable experts.
All advice are welcome with thanks.
Che Kuan Yau (Singapore)

 

[wayne440]

How long will a pump be needed on that particular site?
Maybe hire/rent a pump that will run on the existing utility voltage.

Or hire/rent a suitable 3 phase generator to provide 230/400V.

 

[edison123]

You can rewind the motor for dual voltage of 400 Y / 230 D. Cheap and quick solution.

Muthu

http://www.edison.co.in

 

[che12345]

1. @ Mr. wayne440 (Electrical)16 Jul 22 04:36
"... How long will a pump be needed on that particular site?
Maybe hire/rent a pump that will run on the existing utility voltage. Or hire/rent a suitable 3 phase generator to provide 230/400V... ".
Thanks, valid proposal.
2. @ edison123 (Electrical)16 Jul 22 04:45
"... You can rewind the motor for dual voltage of 400 Y / 230 D. Cheap and quick solution...".
Thanks, valid proposal.
3. Above valid and learned advice are possible circumvention, but short of answering " how to set up a 230V 1-phase source to the VFD to run a 400V 3-phase IM load ". This is a practical case where in remote areas only 230V 1-phase is available. A 3-phase IM is preferred which is very much more reliable than a 1-phase motor which needs a starting capacitor, centrifugal/current switch etc.
4. IEC standard voltage is 230/400V. Most European IM are wound 400V in Delta formation suitable for Star/Delta starting which is widely practised in the field or DOL at 690V linked in Y formation.
All advice are welcome with thanks.
Che Kuan Yau (Singapore)

 

[Parchie]

@che12345 (Electrical),
I am reminded of a job where the owners bought a 230V motor when the available power source was 400V, 3-phase! As you know, LV motors are almost always wired delta. When I saw that the 230V motor was wired delta, I just reconfigured it to wye to solve the mismatch.
Here, you have a 230V VFD but will be using it on a 400V, 3-phase motor--> which might be originally a 230V (delta) motor but just configured as wye (440V). Please check if that is the case.
Otherwise, it would be better for you to have that 400V motor (delta) into 230V (delta)! All you have to do is get the VFD sized properly, as it will be used to feed a three-phase machine from a single-phase supply (set VFD capacity twice that of the motor load).

 

[jraef]

You are over thinking this.

Almost all VFDs are capable of accepting single phase input, so long as they are sufficiently over sized to accommodate the added DC bus ripple and the increased current flowing through the rectifier. Most mfrs will provide you with a de-rate factor that addresses the DC bus ripple issue and that is always higher than the single phase current ratio (x 1.732) anyway. The gross general rule is that if the VFD has an internal DC bus choke, the de-rate factor is 50%, so the VFD is 2x the motor current rating. If the VFD does not have a DC bus choke, then the typical de-rate factor is 60%, so the VFD is sized at 2.5x the motor current rating.

The only other thing to watch out for is whether the VFD has a phase loss trip function and if so, can it be disabled? There are a few brands that do not allow the phase loss trip to be disabled, they are the only ones that cannot be used this way. But a lot of VFD mfrs have figured out that they can protect against phase loss by monitoring the DC bus ripple directly rather than measuring the actual line voltages, and since that is the only problem, it allows the VFD to be used on single phase, which increases the applications they can sell to. So over the years those that disallow a phase loss have caught on to their limitations and have been changing. I don’t even know of any of the major brands that cannot accept single phase left on the market.

Once you get that solved, then you only need to deal with the voltage. If you TRULY only have one leg of the 400V three phase distribution and the neutral to work with, then simply buy a standard transformer for the INPUT side of the VFD, in other words just boost it to 400V single phase, then use a properly sized 400V rated VFD as per above. But if you actually have two phases of the 400V distribution available, no transformer is necessary.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[che12345]

@ Dear Mr. Parchie (Electrical)16 Jul 22 14:10
" ...#1. the owners bought a 230V motor when the available power source was 400V, 3-phase! ... LV motors are almost always wired delta. When I saw that the 230V motor was wired delta, I just reconfigured it to wye to solve the mismatch...." Thanks, useful information but this is not the case. The Motor is rated 400V Delta.
#2. "...Here, you have a 230V VFD but will be using it on a 400V, 3-phase motor--> which might be originally a 230V (delta) motor but just configured as wye (440V). Please check if that is the case.....". No. the motor is 400V Delta. See above #1.
#3. " .... it would be better for you to have that 400V motor (delta) into 230V (delta)! All you have to do is get the VFD sized properly, as it will be used to feed a three-phase machine from a single-phase supply (set VFD capacity twice that of the motor load)...". Thanks, valuable advice. The motor is a standard IEC 3-phase 400V delta with 6 terminal on a terminal block. I can't think of a simple way to change the 400V winding to 230V; unless rewinding it.
Thanks for your valuable advice
Che Kuan Yau (Singapore)

 

[che12345]

@ Dear Mr. jraef (Electrical)16 Jul 22 19:38
" #1. .... You are over thinking ..... Almost all VFDs are capable of accepting single phase input, so long as ......" Thanks, valuable advice. The problem here is a VFD with 230V 1-phase input is NOT able to produce 400V 3-phase output..
" #2. ... The only other thing to watch out for is whether the VFD has a phase loss trip function and if so,...." Thanks, valuable advice. Since the site has only 230V 1-phase power source, I can NOT use a 230V 1-phase VFD as it would NOT be able to produce 400V 3-phase output. Likewise a 230V 3-phase VFD with 230V 1-phass input would NOT produce 400V 3-phasee output. It is impossible for any VFD that is rated for 230V 1-phase or 3-phase input to produce 400V 3-phase output. Phase lost protection, a valuable information ; is not in the picture.
" #3. ... Once you get that solved, then you only need to deal with the voltage...." Thanks for the valuable advice. My need is simple, " how to set up a VFD controlled system to operate on a 230V 1-phase supply to run a standard IEC 400V 3-phase delta wound IM motor".
Che Kuan Yau (Singapore)

 

[edison123]

My need is simple, " how to set up a VFD controlled system to operate on a 230V 1-phase supply to run a standard IEC 400V 3-phase delta wound IM motor".

Asked many times and answered by many in many ways. Now getting tedious.

Muthu

http://www.edison.co.in

 

[davidbeach]

Hint: There's a transformer in your future.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[zlatkodo]

Does it help if you rewind the motor to 230V, Delta?

 

[che12345]

Dear Mr. zlatkodo (Electrical)17 Jul 22 05:59
"...Does it help if you rewind the motor to 230V, Delta? "
Thank you for your helpful advice.
There is no intention to rewind it into 220V 3-phase delta, as it is a portable pump which would be moved to other sites having 400V 3-phase source. In this location, only 230V 1-phase or 400V 3-phase +N 50Hz is available from the utility, where 220V 3-phase is not.
Che Kuan Yau (Singapore)