Fast acting resettable circuit breaker instead of a fuse?

Thread Starter


Joined Mar 31, 2016
I have an SCR which is frequently blowing fuses. We have some good ideas as to why (complex grounding issues for which we are seeking a solution), but want a short term solution which will eliminate the expense of the blown fuses.

Configuration (more detail than you probably want): Resistive load (Moly element heater) powered by SCR through XFMR. Mains are 208 V single phase (two phases of 208 V; no neutral), 60 Amp breaker, SCR is an Ametek HDR Model SHPF1-240-60-CL-01, stepped down to 53 volts by the XFMR. The fuses we have used have been Ferraz Shawmut A70P80-4TA and A70QS100-4IL (lower cost upgrade suggested by Ferraz) and now a Bussman FWH-80B (with "fitter" wiring -- to save money on fuses). These are all very fast acting fuses as required to protect the SCR.

I would like to replace the fuse with a resettable, very fast acting circuit breaker. This would be mounted remotely from the SCR to make resetting easy. Can anyone suggest either generic device names or brand names of what I am looking for? Thanks.


Joined Aug 1, 2013
Been a while since I've had to spec a breaker. When I did, I liked Carlingswitch. Excellent products. Company might have changed hands since then.



Joined Oct 15, 2009
breakers come in all sorts of "time curves" just like fuses..
Find one that meets your "very fast" requirement..

Carlingswitch is still around... Airpax (now Sensata).. ETA.. Square D... Merlin Gerin(Schneider).. Siemens... Eaton and many others..

Thread Starter


Joined Mar 31, 2016
Thanks for the link, etc.

One thing I should have said up front: when I talked with an applications engineer at one of the major fuse vendors, I was told that circuit breakers were not fast enough to protect the SCR, and that I needed to continue using a semiconductor fuse instead. The reason I posted this topic was that I took that opinion with a grain of salt (to my knowledge, that vendor does not make CB's, only fuses ... ).

So I hear you folks flatly disagreeing with the opinion that I need a fuse, but that a properly chosen CB will protect my SCR just fine.