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erlo
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Join Date: Aug 2010
Location: UAE
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220 Vac Supply

04/11/2013 12:32 AM

What are the difference when using the following: Any details to consider?

1. 220 Vac direct from 380Vac - neutral source

2. 220 Vac from a transformer, Say 380 Vac to 220 Vac.
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PWSlack
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#1

Re: 220 Vac supply

04/11/2013 3:10 AM

The only difference is the location of the transformer.

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Doggoneit
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#2

Re: 220 Vac supply

04/11/2013 3:23 AM

220V from a transformer that has not had one leg earthed would give you what is commonly called a safety transformer. The only way to get a shock is bridging active to neutral. There is no path to earth or from earth provided.

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electricalexpert65
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#3

Re: 220 Vac supply

04/11/2013 3:31 AM

Case 1:

220V AC tapped from one phase & neutral of a 380V, 3-Phase, 4-wire system:

i) Fault level would be high, as the source would be bigger

ii) Voltage regulation would be poor, as any drop in the main 380V bus would also affect this control voltage.

Case 2:

220V AC from a 380V/220V Step Down Transformer:

i) Fault level would be lesser, limited by the size of the step down transformer

ii) Voltage regulation would be better, as any mains voltage drop can be compensated with taps in the step dwon transformer.

Advised to use a step down transformer.
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erlo
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Location: UAE
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#5
In reply to #3

Re: 220 Vac supply

04/11/2013 6:45 AM

what do you mean of limited by size? Resistance, winding of transformer, load (ampere) can handle.
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PWSlack
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#6
In reply to #5

Re: 220 Vac supply

04/11/2013 7:20 AM

Try-out some numbers on the forum, perhaps?

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electricalexpert65
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#7
In reply to #5

Re: 220 Vac supply

04/11/2013 7:42 AM

The kVA rating of the transformer
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Tornado
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#4

Re: 220 Vac supply

04/11/2013 4:26 AM

In case 1, the phase supplying the 220V load will have a larger current than the other two.

In case 2, the two phases supplying the step-down transformer will have larger current than the other one, but the imbalance will be less than in case 1.

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Anonymous Poster #1
#8

Re: 220 Vac Supply

04/22/2013 8:45 AM

What do you want to do with the difference of that
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Anonymous Poster (1); Doggoneit (1); electricalexpert65 (2); erlo (1); PWSlack (2); Tornado (1)

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