Build a High Current Power Supply With a Microwave Oven Transformer ⚡️🔌

DISCLAIMER: The information provided is for educational purposes only. Attempt these activities at your own risk. We are not responsible for any injuries, damages, or legal issues that might occur. Always ensure safety and abide by all laws and regulations.

Hello! In this instructable, I'll be detailing the steps involved in modifying a microwave oven transformer for high-current, lower-voltage use. This can be achieved by removing the original secondary windings of the transformer and replacing them with thicker ones. However, before delving into it, it's important to consider the kind of power output you desire. 

For instance, utilising thicker wire with less wire wrap yields higher current but lower voltage. On the other hand, if you use moderately thick wire and incorporate a few extra turns, this will result in high current and moderately high voltage. Keeping the original windings unaltered delivers approximately one to two thousand volts at one to two amps.

Now, let's proceed to establish the materials you will need:

1) A microwave oven transformer

2) An angle grinder, or in the absence of one and if you're up for the task, a hacksaw.

3) 1-5 Gauge insulated copper wire.

4) A grounded three-pin wall plug

Let's move to the next phase!

Step 1: Removing the Secondary Windings

Exciting step ahead! (Although not as thrilling as it sounds) ☺️

Step 1) Position your microwave oven transformer securely in a vice or clamp it onto a solid bench. Then, power up your angle grinder or grab your hacksaw (don't forget to wear proper safety gear).

Step 2) Proceed to cut away the secondary windings; this refers to the lump of thinner wire. Utilise any method necessary to entirely rid of the secondary windings.

Step 3) Typically, there's a slight length of (most likely) red wire beneath the primary windings- the filament windings. Remove these too. Also, dislodge the magnetic shunts, which you can achieve by tapping them out with a flathead screwdriver. Once all these are detached, leaving only the primary, move on to the next instructable!

In the pictures shown below, you'll see what you should achieve. However, in the images represented, I haven't yet rid of the shunts. (The primary connections can be found on the opposite side.)

Step 2: Adding in New Secondary and the Final Product. (VIDEO)

Final phase ahead!

Step 1) Having rid the transformer of the secondary windings, shunts, and filament windings, and ensuring it's as neat as possible, you can now introduce your new secondary wire (of whatever gauge you've chosen). Wind as many turns on your transformer as manageable—the higher the turns, the greater the voltage. Thicker wire yields more significant current. To wind the new secondary, simply encapsulate the new wire around the core of the transformer, replacing where the old secondary was.

Step 2) At this point, you're free to attach your preference on the new secondary's two output leads—whether it's robust, heavy-duty alligator clamps or setting it up for use as a spot welder or stick welder.

Step 3) Take your grounded three-pin wall plug and attach the ground to the base of your transformer. Then, connect both the live wire and the neutral wire to your transformer's primary inputs.

Step 4) Finally, plug it in, power it, and voila! You're the owner of a power supply that could theoretically supply up to a kilowatt of raw output power!

As a visual guide, here's a video with approximately 2-3 turns yielding roughly 3v AC and around 500 amps of steel melting power. 🔥

In the snapshot provided below, you'll find a rewound MOT that I've committed more effort into. It's designed into a power supply with five voltage taps which, once rectified, delivers voltages of 0v (GND), 12v, 24v, 30v, and 50v DC! All voltages excluding the 50v can output over 30 amps, with the 50v capped at around 20 amps.