star / delta transformer

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russellf

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Greetings

A) For any given transformer application, from a purely cost perspective which of the winding configuration options is the most effective 3ph transformer type?
1) delta - delta (primary - secondary)
2) delta - star
3) star - delta
4) star - star
(delta = mesh ; star = wye)
B) For balanced loads, are there any rules which govern the use of star versus delta transformer connection?

(I'm starting on a 3ph SCR half-bridge power supply project and am wondering what the cheapest transformer type would be).

Thanks in advance
russellF
 
Re: star / delta transformer

A. 1
B. If you are referring to a 3-phase load you could use either Delta or Wye secondary. With Delta you would have to come up some sort of ground fault detection and protetion. For a wye system all you need is simple OCPD for protection.

[ October 28, 2004, 04:11 PM: Message edited by: dereckbc ]
 
Re: star / delta transformer

On second thought why even use a input transformer? Use switch-mode, big cost, space, effiecency, and heat savings.
 
Re: star / delta transformer

Greetings Dereck

Thanks for the input. Point taken on the ground fault issue.

Due to the power rating, reliability, development time, cost, etc. switch-mode is not really an option.

Cheers
russellf
 
Re: star / delta transformer

Remember that with a delta it is posible that you can have circulating current that is not posible with a 'Y'. Also, be grounding the "y" not only is GF covered but you'll have a more stable voltage. You can also add electrostatic shielding between the pri and sec windings.
Consider a common drive isolation transformer.
 
Re: star / delta transformer

If you mean 600V. & below,then: delta primary & wye secondary with center of sec.wye solidly earthed & bonded. Yes, electrostatic shielding between pri. & sec. is usually readily available.

If you are not familar with them, then Square D Digest is a good place to start.
 
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