Microwave transformer for 220V to 120VAC

Thread Starter


Joined Mar 3, 2017
I am in US and shall be moving to a different country that has 230V mains supply. I will be needing a step-down transformer to run my power-tools. Was wondering if rewinding the secondary of a microwave transformer would give me a decent 240V to 120V step down transformer?

I am wary of buying those China branded step down/step up transformers with misrepresented power ratings.


Joined Jul 18, 2013
If it was something like the UK you were moving to, they have building site transformers that are 230-120v, one of the smaller ones with two outlets might suffice.


Joined Apr 21, 2014
There are decent step down transformers from reputable brands. For example, if you want to have a fully enclosed unit, Digikey has Triad 250VA and 500VA models available. They are not cheap, but obviously that is somewhat the price of the quality.

If you are assembling your own, you can always connect two transformers back-to-back to step down the voltage. Many ways can be done to accomplish that, but the best one is to have one transformer with a 240V primary and the other one with a 120V primary. Secondary voltages must match. Ideally, each transformer's power rating should match as well.

An example for the 250VA class or a cheaper option for the 100VA class.

Rewinding a MOT only for that is somewhat tricky and IMHO not worth the effort.