Electronics > Projects, Designs, and Technical Stuff
Isolated zero cross detection w/ AC mains
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beduino:

--- Quote from: iroc86 on October 29, 2019, 01:23:37 am ---This is a little different than the welder design I've been thinking about, where the user would select n number of full 60 Hz cycles to apply to the work piece.

--- End quote ---
Depending on spot welder program choosen maybe I'll also apply full 50Hz cycles when more power needed, but I will always start welding somewhere close to mains peak voltage  and the same +/- period.
I'm not expert in this field, but based on very usefull documents mentioned in this thread about inrush currents in the case of inductive load this is a way I'd like to drive my spot welder transformer, which so big, that I consider liguid cooling on its secondary made of copper pipes instead of wires.
Circlotron:
Just thinking about it, seeing a spot welding transformer is meant for a specific purpose, not simply on continuously like most transformers, but dotted on and off, you would think that they would be wound for double the nominal voltage so that there would be no inrush current from saturation. They would then be able to tolerate a full half cycle of input voltage with the core magnetising beginning from zero instead of opposite polarity maximum and therefore not saturating when turned on at the voltage zero crossing. Seeing they are used that way they should be designed that way.
Ian.M:
Why would you do that, which is more expensive in copper and iron, when its relatively simple to avoid saturation at no extra cost if there's a MCU controlling the pulse timing?    It may have made sense back in the days of mechanical timers, but it certainly doesn't in the 21st century.
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