# How can I safely determine the output voltage and current of a transformer?

by Krutik Shah   Last Updated May 15, 2019 19:25 PM

So I am building a Tesla coil with my partner for a senior design project.

We safely ripped out a transformer from a microwave oven. However, after a good amount of research, we were unable to find the maximum output values from the transformer. We know the input values, the standard 120 V and 60 Hz from a US outlet. We need to know the max/peak kV to figure out the capacitance we will need for our primary coil that we need to construct.

Here is what it looks like:

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Consider exciting the high voltage secondary (at 60 Hz) and measuring primary voltage to get an idea of the turns ratio. It should be pretty simple math past that.

I agree with other comments that you might want more experience and/or meaningful oversight from your professors for this project.

MondayTuesdayWednesday
May 15, 2019 18:53 PM

No. Do not use a Microwave Oven Transformer (MOT) for a Tesla coil.

It is the wrong impedance. The output voltage is too low (around 2kV), spark gaps will not fire reliably. The output current is too high (500mA), if it bites you, you will probably die.

The correct transformer to use is an old style (iron core) Neon Sign Transformer (NST). The output voltage of 15kV is plenty to make very forgiving spark gaps. The output current in the low tens of mA may well be survivable if it bites you.

Neil_UK
May 15, 2019 18:57 PM

The part number 6170W1D012G is an LG part. Primary 120v. HT secondary is 2210v 500 mA. If you have to ask, as has been said, you do not know enough to do this safely.

Michael Harvey
May 15, 2019 18:59 PM

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