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I'm designing an inrush current limiter for a large rack which will under normal conditions draw ~25 A at 230 VAC. I'd like to be able to trip the current carrying live wire if the temperature in my thermistor gets too high (temperature not yet defined, likely far above 100°C). Ideally the fuse would be resettable only by manual intervention, e.g. pressing a button or by replacing the fuse with a new one.

My plan would be to mount a thermal fuse physically close to the thermistor. The thermistor would be in series with the thermal fuse.

My problem is that I can only find thermal fuses rated for carrying 25 A or above rated for carrying DC voltages up to around 60 V, not 230 VAC. These seem to be for laptop batteries and mobile phones. Do such devices exist for mains voltage and this sort of current? Or do I have to go for something more complex, like a temperature sensor linked to a relay on the live wire instead?

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  • \$\begingroup\$ s/relay/contactor \$\endgroup\$ – Brian Drummond Feb 20 at 19:10
  • \$\begingroup\$ Where the thermistor is mounted, which type? \$\endgroup\$ – Marko Buršič Feb 20 at 19:28
  • \$\begingroup\$ @MarkoBuršič, the thermistor could be two of these in series. I'd ideally put the thermal fuse between the two thermistors. \$\endgroup\$ – Sean Feb 20 at 19:31
  • \$\begingroup\$ Sorry, I am lost. I don't quite understand your needs, probably nothing similar exists yet. In my opinion, it makes no sense at all. \$\endgroup\$ – Marko Buršič Feb 20 at 19:36
  • \$\begingroup\$ Those NTC limiters do run very hot - they rely on the rise for their resistance to drop to the point that they'll carry the full current. They're designed to operate like that, but you can find soft start boards with a relay that short them out after a couple of seconds to eliminate the steady state loss. ebay.com/itm/… \$\endgroup\$ – Phil G Feb 20 at 19:45

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