AutoTransformer open circuit over voltage?

[Jester]

I just read this ->  https://www.electronics-tutorials.ws/transformer/auto-transformer.html

In disadvantages of auto-transformers, the article states:

"If the secondary side winding becomes open-circuited, load current stops flowing through the primary winding stopping the transformer action resulting in the full primary voltage being applied to the secondary terminals."


I'm trying to make sense of this statement?

[langwadt]

I assume they mean that if you are reducing the voltage and the lower half of winding breaks you have the full input voltage on the output through upper part of the winding

[Andy Chee]

If the open circuit occurs at the point I've marked with a red cross, the full primary voltage will appear at the load.

[Jester]

If the open circuit occurs at the point I've marked with a red cross, the full primary voltage will appear at the load.

Thanks, now I see it.

I was thinking in terms of the load circuit being open, not the actual transformer winding. I was also considering what happens when feeding with split phase 120/240 and one of the fuses opens. In both those cases appears fairly benign.

A healthy sized MOV @ the load, rated just over the lower tapped voltage will cover an open circuited transformer winding scenario.