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Isolation Dry-Type Transformers

Isolation Dry-Type Transformers

Isolation Dry-Type Transformers

Hi All,
Why would we typically use an isolation transformer with the same voltage on the primary and secondary, 1:1 ratio?
Is the reason to improve the voltage regulation, maintain a robust voltage amplitude on the secondary?
What would be the other reasons?

RE: Isolation Dry-Type Transformers

Filter harmonics, or isolate grounds.

RE: Isolation Dry-Type Transformers

Quote (Why would we typically use an isolation transformer with the same voltage on the primary and secondary, 1:1 ratio?)

Please give configuration of isolation transformer, is it D-Y ?

RE: Isolation Dry-Type Transformers

An isolation transformer will degrade voltage regulation slightly.
Source regulation plus or times the isolation transformer regulation.
The transformer may be used to boost a voltage but it is then no longer a 1:1 ratio.
A 1:1 transformer may be used to develop an separately derived circuit, to suppress harmonics or to reduce arc flash, of source imedance

Ohm's law
Not just a good idea;
It's the LAW!

RE: Isolation Dry-Type Transformers

I'm not trying to be a snot, but I might come across as one anyway...

At the risk of being obvious, an isolation transformer's raison d'être is to isolate two circuits from each other, viz., to provide a power transfer but without galvanic connection; unity ratio will be used where no change in voltage is necessary.

I said it m-y-y-y-y way . . . [ with apologies to the late Frank Sinatra ]


"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Isolation Dry-Type Transformers

We frequently used 480 - 480/277 V transformers on large facilities where 277 V lighting was desired to isolate the lighting system ground faults and to eliminate the need to carry a large neutral throughout the 480 V system.

RE: Isolation Dry-Type Transformers

LPS to CR for using “raison d'être” in a sentence regarding engineering.

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

RE: Isolation Dry-Type Transformers

I have used single phase 1:1 isolation transformers to deal with nuisance tripping of GFCIs. Some heating elements' insulation will degrade to the point that it will trip a GFCI at some point in its heating cycle. An isolation transformer eliminates the tripping and any shock hazard, and may be cheaper and more convenient than repeatedly replacing a heating element.

RE: Isolation Dry-Type Transformers

Used them in Faraday cages to isolate the grounds and to massively low-pass filter noise.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Isolation Dry-Type Transformers

As dpc mentioned, isolation or unity ratio transformers are helpful in reducing the fault level in the lighting system and allow
* use of cheaper lighting distribution boards (lower fault rating) as well as
* use of MCBs in lighting and small power circuits.
These are Dyn connected and single phase load on secondary appears as phase-to-phase load on primary system thus reducing the load unbalance in the plant main distribution system.

RE: Isolation Dry-Type Transformers


LPS to CR for using “raison d'être” in a sentence regarding engineering.

C'est apropos, n'est pas?


"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

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