Find your nearest distributor
 Get in touch
 Log in

Are pre-insertion resistors in parallel with the main circuit breakers contacts?

 

Yes. The way a pre-insertion resistor works is that the resistor contacts will close first and will be the only contact in the circuit, then the main contacts will close and both resistor and main contact will be in the circuit at the same time in parallel. At this point the main contacts have the vast majority of the current flowing since the resistance is in the micro-ohm range compared to the 10-10 kilo-ohm range of the resistor (depending on design). The design of the circuit breaker can vary but for the majority of the circuit breakers, once the main contact is closed the resistor will open up shortly afterwards i.e. a few milliseconds, for other designs the resistor may be left in the circuit while the CB is closed.