I have a circuit with a 400V 330uF capacitor a coil with 300turns 1ohm, a capacitor charger and 2 switches, I am trying to find out the max spike current in the circuit. Should I use I = V/R that gives 400A or I = C *dV/dT that is 66A . I use dT 2 miliseconds for the rapid discharging capacitor.

 

You can’t just make up the 2ms figure!

The inductance of the coil will limit the peak current. It will initially rise at the rate of

dI/dt = V / L.

 

You can’t just make up the 2ms figure!

The inductance of the coil will limit the peak current. It will initially rise at the rate of

dI/dt = V / L.

I didn't made up the 2ms I googled capacitors discharge time, so I did the math for L inductance 475uH dI/dt = 840000 A/sec thats crazy!

 

I didn't made up the 2ms I googled capacitors discharge time, so I did the math for L inductance 475uH dI/dt = 840000 A/sec thats crazy!

Why do you say that? What value would you consider reasonable? Would it be too much trouble for you to provide an annotated schematic diagram, or should we continue to try to parse your inadequate verbal description? Your choice.

 

Here is a simulation of a 400V discharge into a 475µH inductor with a 1Ω series resistance. As you can see, the peak di/dt is rather more than you estimated. The maximum appears to be in the neighborhood of 596,000 Amperes/second.

 

Don't touch that
could you share how to add iv to that

I get a error

 

The reason that the current is not what the math shows is simple: The circuit used is not the same as the physical reality. The capacitor is probably not a "perfect" capacitor having zero internal resistance and zero internal inductance. The inductor may only have that one ohm resistance, but what about the connections?? Likewise the switch and the connection wires. Actual zero resistance is only found in simulators and on the cartoon channel of the internet, where it is faked.