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:
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.
6170W1D012G is an LG part number. 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.
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.
To answer the general question, to suss out the basic specs of a power transformer drive it backwards. This is how we did it in engineering school with pole transformers.
You apply 120vac to the HV secondary of the transformer, then measure the voltage on the primary. (Note: Be sure to fuse the 120v supply.) This will let you calculate the ratio of primary to secondary voltage. There was also a way to roughly calculate the current capacity while doing this, but it's been nearly 50 years, so I've forgotten that detail.
The voltage of a microwave oven transformer & the voltage across the capacitor is about 2.1KV The voltage rating should be printed on the capacitor. But like the other guys said: Don't use it for a Tesla Coil. The voltage is too low & the current too high, and it is too dangerous. Use a neon sign transformer. In case you are wondering why such a perfect square wave across the magnetron: The transformer acts like it has an inductor in series. This happens with anything that behaves like a zener and is fed through an inductor, like a fluorescent light, or from a high leakage transformer, like a neon sign tube. The inductor (or transformer secondary) stores energy, then feeds it out into the next 1/2 cycle. When the energy runs out, the potential drops across to the strike voltage of the tube, load voltage (as in a magnetron), or the applied voltage (whichever is less).
Image source: My own experiments - Peter R. McMahon
To measure the voltage, while operating, I would suggest a string of 9 10MΩ resistors in series with a digital multimeter with a 10MΩ input impedance, or an oscilloscope with a x10 probe. Multiply the reading by 10 for the meter, or 100 for the oscilloscope. NOTE: The x10 probe may not handle 1/10 of the voltage across the magnetron before the filament heats up. Use an extra 9MΩ of resistance instead.
To look at the waveform across the capacitor, where both sides are live, the scope can be set to differential mode like a powerscope, using 2 strings of resistors & both channels, set in A+B mode, with B channel inverted. The trace will be the difference between A & B, with B as the reference (ground or otherwise). To measure the current, you can connect the DMM in series, but make sure it is insulated from ground, & KEEP FINGERS AWAY. There's big bities in a microwave oven power circuit.
