Control Transformer Fuse

S

Selinaa007

Member
Location
Canada
Occupation
Electrical Designer
Hello All,

New to the Forum.

What kind of Fuse (Class CC, Class J, or something else) should be used with the transformer in an industrial environment? I am an Electrical Engineer by background so would like to know in detail, any expert advise please....
 
I did a project where the fuses installed by the manufacturer for the control power transformers were all incorrect. They would blow when you energized the MCC bucket, not every time, but about every third time...they provided replacement fuses of a larger rating and paid us to change them.
 
Control power transformer fuses are sized differently than power transformers because of their inrush characteristics.
 
Selinaa007 said:
Hello All,

New to the Forum.

What kind of Fuse (Class CC, Class J, or something else) should be used with the transformer in an industrial environment? I am an Electrical Engineer by background so would like to know in detail, any expert advise please....
Click to expand...
2023 NEC
Is it for a control circuit transformer? Such as a 1,3 or 6 amp fuse?
Is it a dry type transformer such as a 3 phase Delta-WYE?
How 'bout a door bell transformer, just kidding.

TX+MASTER#4544
 
jim dungar said:
Control power transformer fuses are sized differently than power transformers because of their inrush characteristics.
Click to expand...
I use transformer fuses that have a better TCC for this application.

FNQ-R is what I use most of the time because I can remember it without looking it up. It is a class CC fuse like an LPCC. But other manufacturers make something similar.
 
petersonra said:
I use transformer fuses that have a better TCC for this application.

FNQ-R is what I use most of the time because I can remember it without looking it up. It is a class CC fuse like an LPCC. But other manufacturers make something similar.
Click to expand...
Same here. There is no need for a Low Peak fuse on a control transformer, as there is no need for the high speed aspects of a Class J. Years ago I used to use KTK fuses on primaries, but they are not Time Delay and would blow on transformer inrush all too often. Once I switched to FNQs (or equivalent) which are TD fuses, that issue was resolved.
 
I started out with non cc fuses, so had lots of those, and then with cc had boxes of those
Bussman makes a spare fuse holder that self sticks to the inside of a panel door with room for five fuses. But if on the secondary you use small fuses or circuit breakers on loads the xfmr fuse should not blow
 
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