Class J Fuses

timryder

Member
Join Date
Feb 2007
Location
Macomb MI
Posts
176
So I have a tight fitting application which limits me on the components I can choose. I have 4 servo controllers 240v Single Phase and each one of them I would like to fuse the bus supply line. So that gives me 8 total fuses. Well my cabinet which was handed to me and I can't expand the size of (Thanks Mechanical guys) is very tight and I'm questioning whether or not I have to use Class J fuses for these? It's a practice I would typically do but to be honest I don't know why?

Looking for some code or feedback to support the choice of fuse type/class for this situation. Classes M,CC and RK# would be much smaller here. Can anyone offer your support?

Thanks
 
What's the fuse rating? 1.25 x .25 would be the smallest - they are 250V and usually go up to 15A. Most common din rail fuse holders for those little guys are in the 8-12A range so verify the holder before you spec the fuse
 
Looking at using these guys from AutomationDirect.

https://www.automationdirect.com/adc/Videos/Catalog/Circuit_Protection_-z-_Fuses_-z-_Disconnects/Fuses_-a-_Fuse_Holders/Fuse_Holders,_Fuse_Blocks_-a-_Accessories/Class_CC_-a-_Midget_Fuse_Holders_-a-_Accessories_(30A)/EHCC1DU#btn-bar-a

They are Class CC fuses, 30A, 600V.

The fuses are these. https://www.automationdirect.com/adc/Shopping/Catalog/Circuit_Protection_-z-_Fuses_-z-_Disconnects/Fuses_-a-_Fuse_Holders/Current_Limiting_Class_CC/HCLR10

Also Class CC fuses 600VAC rating @10Amp.

I'm satisfied with their specs but im more interested to know if there is a reason to use a specific Class fuse for an application.
 
The servo controllers you are feeding likely have been listed with the Class J fuses, in which case using anything else would void their UL listing. Class J are fast acting and help electronic power devices pass the necessary SCCR values people look for. Using a different fuse would mean the servos were not tested with them, relegating you to a 5kA SCCR, so installing the system anywhere in an industrial environment would be all but impossible.
 
Class J fuses and holders come in multiple sizes, the smallest being roughly equivalent to CC fuses in size. Are you in the smallest J that you can use for your amp rating?

Ken
 

Similar Topics

We normally ground the -24VDC side of a control systems power supply. What are you folks thoughts about grounding the -24VDC side of a class 2...
Replies
1
Views
84
I'm looking for some clarification if anyone here is familiar with UL698a panels. Panel is out of zone/class'd area. with thermocouples extending...
Replies
0
Views
81
Hi, im facing an issue to change the alarm level into another state in the alarm class configuration in Cimplicity. Im trying to change the...
Replies
1
Views
451
Hi - I am searching for an M12 panel receptacles to use for ethernet connections. I see lots of M12 cables that are ATEX / C1D2 rated but nothing...
Replies
2
Views
940
I'm working on getting a handful of devices hooked up to an EWEB card on an Allen-Bradley 1756 PLC using the Ethernet/IP socket interface, and...
Replies
5
Views
1,922
Back
Top Bottom