I'm part of a project in which we are developing a PWM controller for a 24V DC motor.
Our current problem is choosing a capacitor to replace C1, which keeps exploding. We've been running tests at 50Amps which is around the current that will be passing through the motor in normal conditions.
How do we choose the right capacitor in terms of voltage, capacitance, ripple current and ESR?
The capacitor we currently use is the SAMXON KM series 47uF 63V, with 146mA of ripple current and it is clearly under dimensioned. Here is the the simulation using a PWM signal of 4kHz, 50% duty cycle.
The current exceeds by a lot the maximum the capacitor can take but if I change it for another capacitor with higher capacitance and higher ripple current the problem keeps happening, but with higher currents, which makes sense I think.
Finally, one last question: Is the voltage change across the terminals of the batteries we see on the graph bad for them? These are lead-acid AGM batteries from Yuasa: https://www.yuasa.co.uk/batteries/industrial/rec-vrla-cyclic-use/rec36-12.html.
Some of the components we use:
Here is the PCB (older version), PCB layout (current version) and PCB render (current version).
Version with multiple caps, same current passing through each one:
Battery and motor setup, during testing. Both motor and batteries positive poles connected to the middle contact in the controller, motor negative connected to the right, battery negative pole connected to the left. The other motor is connected to a couple of high power resistors to generate load.