Decoupling capacitor and inrush currents

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1

Hi all,

So we’re checking on the odrive as a replacement of some other not to be mentioned controller which was adviced to have a decoupling capacitor as we did use. Now, this led to huge inrush currents for which we had to take account in the design of our power distribution board and battery. Now, we’re trying on the odrive and wondering, is it advised (we could not find) to use a decoupling capacitor and if so, for what cause?
If so, what capacity are we talking about?

Secondly, if not, what kind of inrush currents can we expect on the odrive during power-on?

We’re using 2 motors per odrive on a ± 50V power supply.

2

ODrive includes the DC link capacitance on board. It’s always a good idea to use a precharge circuit with motor controllers as the capacitance can be significant.

I’m not sure exactly what inrush current you can expect to see from ODrive in your setup, but there is no precharge circuit built in, so if you’re worried about it you should implement one.

3

Thanks for the advice!

With a precharge circuit, you mean the preventing of inrush currents with for instance a hot-swap controller?

You say the ODrive includes a DC link capacitance, with that you mean the need of an extra decoupling capacitor is not present?

4

A precharge circuit is usually just a relay and a resistor. The drive is connected through the resistor until the voltage is sufficient, then the relay closes to allow full power through. That’s just done to keep the current low.

You do not have to add any additional capacitance.

5

If you had to make an order estimation, what input capacitance can we expect? 50uF?

6

If you mean “how much capacitance does ODrive have on board?” it’s ~3.7mF for the 24V version and ~1mF for the 56V version.

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