I wanted to build a foam cutting tool and thought of using one of my microwave oven transformers to make a 6v/12v power supply. I am microelectronics guy, not a power guy so it has been 30 years since my college EE transformer course
There are many options, a tapped transformer, multiple multi-volt windings, multi same volt windings series or paralleled, etc. I was thinking of using 2 windings. The transformer is a standard MOT with the primary wound horizonally and the secondary parallel to and above the primary. I wanted to cut out the magnet wire secondary and imagining that it is 1 turn per volt in stepdown, I would make two, 6 turn secondaries. using a switch to put them in series I would get 14V with maybe 2 to 4 amps and connecting them in parallel I would get 6V at double the current. I would control the output voltage with a light dimmer on the primary. My questions:
1. What guage for the secondary? AWG 18 stranded? Has to handle the amps but be bendable and fit in the space.
2. Assuming the primary looking down from above is wound CCW, do I have to wind both the secondaries CCW as well?
3. Does it matter how I wind the secondaries? Put the wires next to each other and wind both at the same time? Wind one on the botom of the secondary space and the other above it? Wind one around the center of the core and then wind the second one around the outside of the first one? Maybe since I am using only one winding at a time, it is irrelevant?
4. Should I be aware of anything else or re-think my design?
5. Any tricks or things to limit core saturation and heating?
6. I'll need a hefty DPDT Switch. Do I need to worry about transients if I switch voltages with the dimmer on the primary and the power still applied? I want to be sure I don't blow the dimmer or arc the switch.
7. Should I be concerned if the hot wire breaks and I am running the transformer under no load (secondary open)?
Thank you.
There are many options, a tapped transformer, multiple multi-volt windings, multi same volt windings series or paralleled, etc. I was thinking of using 2 windings. The transformer is a standard MOT with the primary wound horizonally and the secondary parallel to and above the primary. I wanted to cut out the magnet wire secondary and imagining that it is 1 turn per volt in stepdown, I would make two, 6 turn secondaries. using a switch to put them in series I would get 14V with maybe 2 to 4 amps and connecting them in parallel I would get 6V at double the current. I would control the output voltage with a light dimmer on the primary. My questions:
1. What guage for the secondary? AWG 18 stranded? Has to handle the amps but be bendable and fit in the space.
2. Assuming the primary looking down from above is wound CCW, do I have to wind both the secondaries CCW as well?
3. Does it matter how I wind the secondaries? Put the wires next to each other and wind both at the same time? Wind one on the botom of the secondary space and the other above it? Wind one around the center of the core and then wind the second one around the outside of the first one? Maybe since I am using only one winding at a time, it is irrelevant?
4. Should I be aware of anything else or re-think my design?
5. Any tricks or things to limit core saturation and heating?
6. I'll need a hefty DPDT Switch. Do I need to worry about transients if I switch voltages with the dimmer on the primary and the power still applied? I want to be sure I don't blow the dimmer or arc the switch.
7. Should I be concerned if the hot wire breaks and I am running the transformer under no load (secondary open)?
Thank you.