I am in bit of predicament.
I have a 3phase 230V System which uses 3 motors and contactors.
1 nos 1.1KW 230V motor
1 nos. 60W
1 nos. 40W
All motors has 3phase 3 wire connections

My supply is 400V.

My idea is a transformer.
Never tried this, but will 3 separate transformers do?

 

You could use 3 separate transformers if that's all you have access to, but it would make more sense to use a single 3ph transformer.

 

Hello,

3 Phase transformers usualy have 3 legs with the coils on each leg.
They can have various configurations like delta and why connections.
Read the attached PDF's for more info.

Bertus

 

If your supply is 400V, it would be unusual if it were anything other than 230V phase-neutral, 400V phase-phase.
The 230V 1.1kW motor is most likely 230V phase-neutral, because 230V phase-phase (132V phase-neutral) is also unusual.
So, I think that the most likely situation is that your motors are already correct for your supply.

 

If your supply is 400V, it would be unusual if it were anything other than 230V phase-neutral, 400V phase-phase.
The 230V 1.1kW motor is most likely 230V phase-neutral, because 230V phase-phase (132V phase-neutral) is also unusual.
So, I think that the most likely situation is that your motors are already correct for your supply.

Thanks, I did not even consider where OP lives (Maldives). When my brain sees "400V" it automatically defaults to "foreign equipment, transformer required."

I looked it up and Maldives uses 400V, 4-wire three phase. So you are almost certainly correct, but if @R!f@@ could post a picture of the motor nameplates we could say for sure.

 

If you mean using three individual transformers in place of the single unit type, Done this a few times, with no problems as any three phase transformer is just three 1ph ver mounted in the same laminated frame.

 

Check pricing on a full installation. You’ll likely find a single 3 ph will be most eceonomical. An auto transformer may save even more

 

Check pricing on a full installation. You’ll likely find a single 3 ph will be most eceonomical. An auto transformer may save even more

I am in bit of predicament.
I have a 3phase 230V System which uses 3 motors and contactors.
1 nos 1.1KW 230V motor
1 nos. 60W
1 nos. 40W
All motors has 3phase 3 wire connections

My supply is 400V.

My idea is a transformer.
Never tried this, but will 3 separate transformers do?

you can try an Open Delta configuration with two single-phase transformers

 

You need qty 3 single ph transformers in place of a single 3ph to create equivalent.

 

If the TS has three single phase transformers of adequate rating tghen that is the way to go. If the TS does not have any transformers then price comparison shopping is what I recommend. If delivery time is a concern then probably single phase transformers are more likely to be in stock. AND, as already mentioned, if there happens to be a failure in the future, an open delta configuration can serve in an emergency, but only delivering 2/3 the original power.
So there are quite a few things to consider when making the choice.
Can the TS accept a 28 week lead time for a custom transformer??

 

I am in bit of predicament.
I have a 3phase 230V System which uses 3 motors and contactors.
1 nos 1.1KW 230V motor
1 nos. 60W
1 nos. 40W
All motors has 3phase 3 wire connections

My supply is 400V.

My idea is a transformer.
Never tried this, but will 3 separate transformers do?

Here is some theory on an Open Delta connection with two transformers, very commonly used:

https://studyelectrical.com/2019/11/open-delta-v-v-connection-of-transformers.html

Need to watch for the derated power capacity, but looks like you are not needing much power

 

The diagram clearly shows the connection. I cannot post it as it is stamped by client...so I do not want any legal issues.
The three motors have 3 wires coming from phases.
So it is 230V delta.
I can show the grinder motor plate . All motor have the same 3P3W connection.
It was a mistake when they placed the order. Client said 220V, manufacturer went for 220/230V 3 phase.

 

If the TS has three single phase transformers of adequate rating tghen that is the way to go. If the TS does not have any transformers then price comparison shopping is what I recommend. If delivery time is a concern then probably single phase transformers are more likely to be in stock. AND, as already mentioned, if there happens to be a failure in the future, an open delta configuration can serve in an emergency, but only delivering 2/3 the original power.
So there are quite a few things to consider when making the choice.
Can the TS accept a 28 week lead time for a custom transformer??

Hello.
Are you offering me one.
If that is the case, you should consider shipping to Maldives.
I am looking into Aliexpress suppliers and checking prices.
I need to check the machine and see is it 4W connection or 3W supply.
As the diagram shows 3P4W but I cannot see a4W terminal but a 3W supply input from the machine.

I can always put phase failure relays to protect winding failure damage. It's no biggie.
I cannot go for open delta, as the machine will run for hours on end.
All motors will be in operation as this is a sharpener.
The grinder, sled motor and pump.
So 100% loaded for 6 hours atleast

 

What would happen, if I were to remove motor and check winding to see if it can be changed to a STAR connection.
It should work with 3P4W.

 

OK, and no, I was not offering to provide a transformer, I WAS suggesting a way to work around the problem that could cost less and probably be available in less time.
As neither of those are acceptable I suggest another scheme, which is to use a commercially available variable speed drive package. These rectify the incoming power to DC and then use an inverter to generate the 3-phase power at a suitable voltage and frequency. VS drives are available from many sources and are lighter than transformers.
An added advantage is that they are often stock items without extended lead times.

 

What would happen, if I were to remove motor and check winding to see if it can be changed to a STAR connection.
It should work with 3P4W.

Changing to wye/star would make matters worse.

 

VFD was an option I was thinking
But I need to use 3 of them u know.
And also a bit of wiring change too.
Need to get rid of the contactors and a lot of rewiring.
Could be cheap but too complicated for the client too.
If I did tht he would need me every time to deal with issue. Which is good in a way but bad since I am rather bzy.
So hassle free option is one I want.

 

Changing to wye/star would make matters worse.

Ya. Might reduce torque, right?
But would it?
The motor will see the rated voltage across its windings....no?

230V at delta is what it requires.
So, it would still see 230V at star with 400VAC 4 wire input.

What do u say?

 

Ya. Might reduce torque, right?
But would it?
The motor will see the rated voltage across its windings....no?

230V at delta is what it requires.
So, it would still see 230V at star with 400VAC 4 wire input.

What do u say?

Oh, sorry I misunderstood. I am not doing a very good job in this thread so far.

I thought you meant to put the motor in wye configuration across 230V which would put (1/sqrt(3))*230V=133V across the windings.

But of course you didn't mean that. That is stupid. You don't even have 230V, that's the whole problem isn't it?

You meant put the 230V delta motor into wye so that you can connect it to 400V without any transformer, right? If so, then yes, I think that should work. (1/sqrt(3))*400V=230V so each windings should see the correct voltage it is rated for.

There is no wye/delta start circuit, correct?

 

If the motors all run the same speed then one drive might power them all. Then the cost would be less, probably.