Arduino - High voltage transistor control

[ejectoseatocuz]

According to the manufacturer (JCCON), its around 0.12 Ohm.
A link to the capacitor I bought: https://de.aliexpress.com/item/1005002111767132.html?pdp_npi=2%40dis!USD!US%20%244.23!US%20%240.25!!!!!%402100bddb16616274581581423e8a75!12000020608705319!sh&spm=a2g0o.store_pc_home.productList_6000558625405.pic_0
I got it somewhere else, no advertising intended.

The capacitors right now are rated 400V with 680uF. Theyre not the original ones I got, they were a little cheaper - if something goes wrong, I dont wanna loose that much money on good caps. Obviously, I wont use the full 400V - I guess 250V is more than enough for those, especially considering their price

[DrDiettrich]

@ejectoseatocuz

rated 400V with 680uF

Don't wonder if the capacity at that voltage is only a fraction of the indicated value.

[cedarlakeinstruments]

@ejectoseatocuz

I dont wanna loose that much money on good caps

OK. As long as you realize that a bad cap exploding in your face can cause you to lose your eyes!

[johnerrington]

@ejectoseatocuz

I am trying to achieve a time-able electromagnet. Since the copper wire in the coil has a certain resistance x (plus inductivity), to achieve higher current you need to raise the voltage levels. I will do this step by step, stating at around 40V with the possibility of around 400V DC (now thats the maximum voltage that the boost module can provide). That then charges up a capacitor, 500V 680uF (short circuit safe, and protected by diodes (but thats a question for another day)) who will, controlled by the IGBT, dump its charge into the coil. Now whats a little difficult to solve (and what eliminates a simple thyristor configuration) is that the coil probably will need to be turned off earlier than the capacitor has fully discharged

If you match the coil inductance to the capacitance you will be able to find a point where the voltage - a decaying sinusiod - will drop below zero at the time you require.
You can adjust this for different timings by switching capacitors in or out.
You can then clamp the negative part to dump the remaining energy in the coil.

[ejectoseatocuz]

Absolutely! Been there, done that. It was only a 16V one, but that was enough. Don't wanna find out what happens if those ~50 Joules do explode.

[ejectoseatocuz]

Thats indeed a good idea, Ive already thought about going down that path some time later, i've seen other people do that too. I wanted to keep it simple for now. Thanks for the suggestion!

[johnerrington]

@ejectoseatocuz

I wanted to keep it simple for now.

Its a LOT simpler than trying to interrupt the discharge.

We still dont know WHY you want to do this "timeable electromagnet".

[ejectoseatocuz]

The project is supposed to be an automatic hammer for small metal sheet processing (mostly bendig over a curved surface). Since it can be assumed that not every single activation will result in the exact same runtime (if the inlay weighs slightly more or less than the one that the caps were calculated for thats already an issue), I need a system that allows for some kind of variable timing. Hence this whole thread.

[cedarlakeinstruments]

I see.

Have you considered storing the energy in something like a flywheel or a spring instead of a capacitor? That might make it more manageable and robust.

[DrDiettrich]

@ejectoseatocuz

automatic hammer

In this case the hammer most probably is the magnetic core of the coil. The force of the hammer can be limited by the provided voltage, and by the width of the power pulse.

I'd implement the safety cut of the high supply voltage by a main contactor as high side switch and a FET for the low side pulse switch. Possibly recuperation of the coil energy into the capacitor can be achieved by a properly routed freewheel diode.