How to deal with inrush current tripping circuit breakers

currentcurrent-limitinginrush-currentprotection

I have a temperature controller supplied with 230VAC via a 0.5A circuit breaker curve C. The thing is, the MCB trips as soon as power is turned on. I have measured the inrush current profile without the MCB with a current probe: up to 90A for 20ms!

I can see three options:

  1. A capacitor is first charged when power is turned on, and a second "power" switch allows the capacitor to discharge. I don't want another switch, so I'd rather avoid this option.
  2. A RC + MOSFET ramps up the voltage. If possible and safe, I'd like to avoid adding components as it is a real hassle to go through the design update process.
  3. The 0.5A nominal is changed for 10A. This is the quickest option as I have some around and it doesn't take much to change a value on a drawing and get it signed off; however that allows more potential destructive power in the downstream components (a couple of relays, a AC/DC, in addition to the controller). The technician used the same wire gauge everywhere, so up to 10A wouldn't melt the wires.

Is there any other option I am not aware of? If there isn't, then this post serves to those in the same situation. After all that's what forums are for.

Best Answer

NTC inrush current limiter, might be an option if you can find one that fits your requirements. The NTC inrush current limiter is a negative thermal coefficient in other words its resistance decreases as it warms up, so this devices limit inrush current by acting a series resistance and as current goes through it warms up and its resistance drops allowing higher currents to go through. You can check more info in wikipedia Edit: This previous answer looks like it might be helpful.

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