Need a 380Y/220 transformer

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electrofelon

electrofelon

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Cherry Valley NY, Seattle, WA
I've got a small mixer I need to power. It needs 3 phases plus a neutral and my premise system is 240V, thus I need a 240 delta to 380y/220 transformer. The motor is only .75 KW. I can find such a transformer no problem however the smallest one immediately available is 3KVA and a couple grand. It won't be used much and isn't really a prize anyway so I'm just trying to come up with a cheaper option. It's an annoying voltage, he's trying to come up with another more common transformer that would have the same ratio and nothing works. I thought about making up my own Delta/Wye Bank out of single phase control transformers. I would need 240 to 220 volt transformers. Can't even find those. Anybody got any nice creative bastard solution I may have overlooked?
 
Use (3) single phase 240:240V transformers connected in secondary wye. Then use three buck-boost to lower the voltage to 220V.
 
1) What is the frequency rating of this mixer? Will 60Hz operation make it run faster, and might need a higher voltage to maintain V/Hz ratio?

2) Getting your desired voltage with standard transformers:

Use three of these transformers:

Use a _single_ 240V coil in each transformer as your primary, use the second 240V coil connected to the 24V coils in a buck configuration as the secondary. This gives you a 216V secondary.

Connect the 3 primaries in delta to your 240V supply, connect the 3 secondaries in wye.

Alternative approach:
use a single 240V coil in series with the 24V coils in a _boost_ configuration as your primary, and a single 240V coil as your secondary. This gives you a 264V primary :240V secondary, but used at 240V: 218V . Again delta:wye

The transformers are normally rated 500VA. As I am suggesting using them, I think that you end up with about a 225VA rating, or 675VA when banked.
 
winnie said:
1) What is the frequency rating of this mixer? Will 60Hz operation make it run faster, and might need a higher voltage to maintain V/Hz ratio?

2) Getting your desired voltage with standard transformers:

Use three of these transformers:

Use a _single_ 240V coil in each transformer as your primary, use the second 240V coil connected to the 24V coils in a buck configuration as the secondary. This gives you a 216V secondary.

Connect the 3 primaries in delta to your 240V supply, connect the 3 secondaries in wye.

Alternative approach:
use a single 240V coil in series with the 24V coils in a _boost_ configuration as your primary, and a single 240V coil as your secondary. This gives you a 264V primary :240V secondary, but used at 240V: 218V . Again delta:wye
Click to expand...

1) the motors have drives, and they say 50/60hz.

2). I thought about Buck boost, but I can't get a usable neutral with y-connected auto transformers correct?
 
electrofelon said:
1) the motors have drives, and they say 50/60hz.
Click to expand...

Ok. You might double check the drive maximum voltage rating; if the drive can tolerate 416/240V then you have a few more options.

electrofelon said:
2). I thought about Buck boost, but I can't get a usable neutral with y-connected auto transformers correct?
Click to expand...

Yes, but my suggestion is actually using the 4 coils of a standard transformer in an isolating connection. That is why you get less than half of the rated transformer VA.

The transformer normally has 2 primary coils connected in parallel for 240V or series for 480V. I suggest using one of these coils as a 240V primary and the other as a 240V _isolated_ secondary. Bang, 1/2 the normal VA rating. Then you use the 24V coils to adjust the secondary voltage in a 'buck' fashion. So the standard 240x480:24x48 transformer is being wired as a 240:216V isolating transformer.

-Jonathan
 
Here is one of the drives. It doesn't give voltage range, just the nominal. The other drive is for a small motor that appears to be single phase 220 volt input. I don't have a picture of that handy
 

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If it's a 380Y/220 transformer is there a possibility that it needs a 50Hz transformer?​

 
winnie said:
Bang, 1/2 the normal VA rating. Then you use the 24V coils to adjust the secondary voltage in a 'buck' fashion.
Click to expand...
Since you are limiting yourself to half the nominal rated VA anyway, I infer that for simplicity it would suffice to use a single 24V coil and leave the 4th coil unconnected? Particularly since you are wiring that 24V coil in series with a 240V coil, so the 24V coil current will be way below rated capacity anyway?

Cheers, Wayne
 
electrofelon said:
I've got a small mixer I need to power. It needs 3 phases plus a neutral and my premise system is 240V, thus I need a 240 delta to 380y/220 transformer. The motor is only .75 KW.
Click to expand...
Unless there is something really special about this machine, seems would be about as easy or even cost effective to get a machine rated for what you have for supply?
 
kwired said:
Unless there is something really special about this machine, seems would be about as easy or even cost effective to get a machine rated for what you have for supply?
Click to expand...
Possibly but that is above my pay grade. I know I did say small, but this thing stands like 5 ft high, the mixing reservoir is maybe the size of 5 gallon pail. I would guess even the correct transformer would cost less than buying a new one of these.
 
winnie said:
Actually:

I'd check the motor to see if _it_ can be field wired for 220V, and if so I'd ditch the drive and replace it with something like:

-Jonathan
Click to expand...
If the drive is more of an OEM thing it may have limitations.

A more general use drive like from A-D can be programmed to a specific output voltage. Might not be possible however to get over 240 nominal output from a drive rated for up to 240 nominal input and may need to get into the 480 volt drives and supply it with a step up transformer. At only .75 kVA I'd probably get a 2 HP drive and supply it with single phase - it can handle single phase in three phase out even though the instructions don't mention it for the 480 drives for some reason yet several of their 240 volt drives do mention this. I have hooked their 480 drives to single phase input before and they work fine just need to double the drive rating so you don't overload the front end rectifier.
 
jim dungar said:
Autotransformer connection, like buck-boost, cannot be used to go between delta and wye.
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The proposal is effectively a 240V:240V isolation transformer, followed by a 240V:216V autotransformer. It just puts it all together in one package on a single core, with the 240V isolation secondary coil the same physical coil as the 240V autotransformer "primary" coil.

Cheers, Wayne
 
jim dungar said:
Autotransformer connection, like buck-boost, cannot be used to go between delta and wye.
Click to expand...
But it _isn't_ an autotransformer connection. The transformers I suggested have _4_ coils. A-240V, B-240V, C-24V and D-24V. The connection that I suggested is an _isolation_ connection to go from delta to wye, followed by autotransformer connections to buck the voltage. Just rolled up into a single 4 coil transformer rather than using separate 2 coil transformers.
 
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