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Inrush resistor bypass with timer relay

mike buba

Hi,

I have a high inrush current when turning on the equipment and I have now added an inrush resistor in series. The problem is that the resistor gets hot over time and the re-start can be done only when the resistor cools down, approx. 3-5 minutes after last turn off or trip.

I was thinking of adding a timer relay in the circuit that would bypass the inrush resistor a few seconds after the start.

Are the idea and schematics okay? Is there a more elegant way of doing it?

Thank you in advance.

  • 0

    I can assure you that this sort of solution to inrush  is quite common, Chint for example  do a timer you could program to pull in the delay contactor. However, during a single start up the resistor should not be getting half way to failure temperature, as if does the lifetime will be short. Then the odd double start in rapid succession should be survivable. how long does  the run-in need to be before bypassing the resistors, and how fast do you expect a restart, that will size the heatsink on the resistor. Above about  half a kW consider water/oil cooled resistances may be worthwhile.

    Mike

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