Assembly is straight forward but:
- Make sure to use a 2oz cu PCB. The high current paths on the AC side are generouse and include traces on both sides but 2oz is required to keep temperatures down.
- Use 16AWG stranded copper cords if possible. Check drill hole diameter if you do. I've used 18AWG and have gotten away with it running a 1300 watt space heater but the plug gets hot - like 50C. Measured case temp is around 35C. Note, the internal temperature sense is set to trip at 100C.
- Making the flyback inductor is easy.. What's most important is the winding polarity. For ease of winding & handling I use 26AWG although there's no penalty for 28AWG or even 30AWG on the secondary; it just gets fragile. I use MW35-C HY magnet wire.
- Primary: Np=6. Start winding to right side (wire pointed away from body) with wire coming out bottom of core.
- Secondary: Ns=17. Start winding to right side (wire pointed away from body) with wire coming out bottom of core. Start same side as primary termination. Wind each side secondary half-way around core.
- Both windings should be evenly spaced around the entire core to minimize leakage inductance.
- Here's a picture of the completed primary:
And with the secondary (primary @ top of pic, secondary @ bottom). Note that the top right wire (primary) is on top and the bottom right wire (secondary) is coming out the bottom of the core) - that is the correct polarity.
- Don't worry if the loops are a bit loose like those in the picture or the spacing isn't perfect. The ferrite core has a relatively high permeability and is forgiving in that respect. Be sure the wire isn't nicked and test for shorts when done.