Isolation Transformer - Use One!

[SteveNielsen]

Re: Isolation Transformer - Use One!

I used to have one, same principle as used the UPS with AVR. The relay clicking is very annoying when input live Voltage varies a lot.
Example of more complicated one (not using auto-transformer) than the one in yours, but same idea.

Lots of newer regulators us TRAIAC instead of relays.

Interesting info. I can understand how the clicking gets annoying. It doesn't bother me much, just another noise in the house and at least I know what it is.

I would like to find a schematic for this one so I can see how it is switching between output voltages. I think I'll start another thread about it over in power supplies forum and not hijack this one.

[Per Hansson]

Re: Isolation Transformer - Use One!

Might be something similar to this:

https://www.badcaps.net/forum/showth...715#post473715

EDIT: OMG 3000:th post in only 10 years, my oh my!

[fzabkar]

Re: Isolation Transformer - Use One!

Example of more complicated one (not using auto-transformer) than the one in yours, but same idea.

The block diagram shows an auto-transformer for switching between taps, and a "stepped down transformer" for generating the DC supplies for the electronics.

[budm]

Re: Isolation Transformer - Use One!

But the same concept, you use the Autotransformer to do the boost or buck buy switching the taps, and the electronics to drive the relays based on AC input Voltage. page 22, 26, shows the basic AVR, table 3 shows stabilized 214VAC output with input capture range of 150VAC ~248vac.
Tap switching AC regulator has been around for decades. You can also use motor drive Variac, MONSTER power uses that in one of its home unit.

[fzabkar]

Re: Isolation Transformer - Use One!

The first tap-switching AVR I encountered was a Topaz unit in 1981. I was supposed to stabilise the supply for a minicomputer, but it was a useless buzz-box that just made things worse.

[SteveNielsen]

Re: Isolation Transformer - Use One!

You guys are right. I finally sussed it out. It is an autotransformer with a center-tapped tertiary winding to supply power to the electronics and relay coils.