Isolation vs regulation in Power Transformers

[kingtutley]

I don't understand the differences between types of transformers. Specifically, what are the differences between isolation transformers, regulating transformers, and power transformers.

I was under the impression that ANY transformer, with the exception of autotransformers, were isolating and regulating devices. What part of theory did I miss?

 

[Skogsgurra]

None, I think. Might be a question of defining the word "regulating".

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[tinfoil]

It has to do the the main purpose of the xmfr.

An isolation xmfr is being installed mainly to create isolation, typically for fault limitng but increasingly for harmonic mitigation.

A regulating xmfr (typically with automatic on-load voltage control) is primarily intended to control/regulate the load-side voltage around a set point.

A power transformer usually incidcates a larger device thana distribution xmfr, but this one varies a lot by region.

 

[kingtutley]

Ok, so I see that a regulating transformer would have some sort of secondary control to maintain the turns ratio so that whatever voltage is applied to the primary, the secondary voltage remains within some sort of band.

But, again, if all transformers are, in a sense, isolation devices (agin with the exception of autotransformers), what makes them different? I read something about separate windings and insulation, but unless it's an autotransformer, those are a given for all of them. I also read something about separate bobbins, but other than separating them physically more than they are already, what difference would that make?

 

[dpc]

Some smaller dry-type transformer are fitted with an electrostatic shield between the primary and secondary windings to (supposedly) reduce line noise and interference being passed between the windings. It may help reduce certain types of interference. Google "shielded isolation transformer".

But basically, any two-winding transformer is an isolation transformer.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[bacon4life]

Could isolation transformer also refer to a separately derived source? I am not quite sure I would refer to a grounded wye-grounded wye transformer with graded neutral insulation as an isolation transformer.

Thinking about a current transformer, the voltage and current on the secondary side are completely isolated from the common mode voltage between ground and the high side terminals.


From Std C57.12.80
regulating transformer: A transformer used to vary the voltage, or the phase angle, or both, of an
output circuit (referred to as the “regulated circuit”) controlling the output within specified limits, and
compensating for fluctuations of load and input voltage (and phase angle, when involved) within specified
limits.

power transformer: A transformer that transfers electric energy in any part of the circuit between the
generator and the distribution primary circuits. See also: distribution transformer