1756-OB16E Electronic Fusing

[remlapw]

Hi there, I have a customer that has a specified standard of using a 1756-OB16E module with a 1492-IFM20D24 LED indicating interface module. In the past I have always used these modules with external physical fusing - usually by utilizing a 1492-IFM20F-F24-2 (fusible, with blown fuse indicators).

Can someone explain to me how these E-fuses work? From some investigation I can see that when added into my controller configuration in RSLogix5000 I gain access to the "Local:7:I.FuseBlown.0-31" tag

From the AB manual page 149: http://literature.rockwellautomation.com/idc/groups/literature/documents/td/1756-td002_-en-e.pdf
it specifies a max 1A/point, 8A/module and says they are fused per group.

What is the trip rating/time on these e-fuses? my understanding is that it's typical for an e-fuse to control a latch (as they inherently reset themselves after cooling off). Does this mean there are 16 individual e-fuses (8 in parralel to a latch) to come up with the 2 groups?

Last question - How are these reset programmatically? through an SSV?


Thanks,
Rem

 

[rootboy]

It looks like it's 1 amp per point up to a maximum of 8 amps per module.

The OB16E doesn't seem to have fault reporting like the OB16IEF module does, so I think that it will reset itself.

Anybody know for sure?

 

[remlapw]

I can confirm that in the module properties there are 2 buttons for resets on the E-Fuses. Would seem pretty useless if they reset themselves, never mind a trouble-shooting nightmare.

There are 2 resets, I am wondering if the group current needs to beyond 8A for it to trip for that group. This could pose a scenario in which all of that current is from one point (which would exceed the 1A specified) and that output would then fail.

If i had one of these modules on hand I would test with a high wattage low ohm resistor across the output to common, provided I had one of those as well....