Resistors are an important part of capacitor charge and discharge circuits. At the start of an application where the capacitor has to be charged and a voltage is applied across a capacitor, initially it appears like a short circuit. A circuit with no pre-charge can cause a large voltage difference and a sudden high inrush current. This will end up causing damage and in some cases cause welding of the relay contacts leading to further damages.
On the other end, resistors are also required as Capacitor Discharge resistors or Bleeder resistors, which are typically applied across a capacitor with an intention to safely discharge the capacitor of any residual electric energy remaining.
In both applications, it is important to identify a resistor with the right energy capacity.
Here below, we provide a single pulse pre-charge/ discharge calculator. In real life applications, the number of inputs or considerations could be many. The calculator below is a basic determination for the energy.
For repetitive pulses and for applications with more considerations, KWK engineers will be more than happy to assist!
1. Resistance Value --
2. Discharge Time --
3. Pulse Energy (E) --
4. Peak Power (Wpk) --
5. Average Power (W) --
If you're not confident about these variables, you can give us a call or an email and we’d be happy to help in braking resistor sizing.