Inrush current limiting

Thread Starter

Jake P.

Joined Nov 7, 2019
I am using an AC to DC converter and I need to limit the inrush current. I've read about using NTC thermistors to limit the current, but I was wondering if there was a better way to do this?



Joined Jan 29, 2010
Looking at the spec for that device, the 20A inrush is a device current limit specification,, why do you think extra limiting is required.?
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Thread Starter

Jake P.

Joined Nov 7, 2019
The extra limiting would be used so that I can increase the capacitive load of the converter. I contacted Recom about this and they did not really give me an answer.


Joined Oct 7, 2019
NTC thermistors to limit the current
That works if the NTC is cold. (cold start)
If the power supply has been running and the power drops for one second it will not work. The NTC is hot.

Some times I see a fixed resistor with a relay contact across it. The relay has a 1 second delay before it shorts out the resistor. That works with "power line flicker".


Joined Apr 20, 2019
I am using a RECOM RAC15-24SK and the expected in rush current is about 20 Amps maximum.
@Jake P.
Why do you believe that the inrush current will be substantially altered by the size of your capacitive load? Have you measured the inrush current under load conditions of small and large cap loads? The inrush current is primarily a measure of current needed to charge the input capacitors of the converter, not to charge the load.


Joined Jan 23, 2018
This is one more case of information lacking to define the context of a question. How big is that capacitive load? And what is the current limit of the converter? I see what looks like an estimated inrush current but that would be a very short current spike, not nearly enough to trip even a fast circuit breaker. Aside from that, many power supplies are current limiting, so that the supply output will be held to some safe value. And based on the listed input current this is not a high powered system supply. So please answer the questions and avoid getting guesses.