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500 V 125 Amps fuse body getting overheated(80 c) in only L1 Phase issue.

Rohit Sharma

Hello All Team Members,

We have one 3phase SFU fuse unit feeder in 400V LV distribution panel. This feeder feeding to load which having thyristor (IGBT) control heaters with 70 amps full load capacity. 

When we switched ON this SFU unit to supply 3 phase 410 VAC power supply to load then after some time the fuse body temperature of L1 phase has reached up to 82 deg. Celsius...while other L2 & L3 fuse temperature were around 62 deg. only... & checked the three phase Current & voltage which were L1 - 66 amp, L2 - 66,6 amps , L3 - 67,7 amps & V1& 2 - 404,8 V, V2&3 - 404,9 V, V3&V1 - 405,3 V. 

Same time checked the 3 core cable temperature which was around 37 deg only. 

All three fuses also replaced with new one. Fuse type is NH00, Make - EFEN. 

Kindly share your valuable comment. 

Parents
  • 0

    When you replaced the fuses, did you still see L1 fuse hotter than the other two? If so I'd be looking to see what is different between the phases, either about the detail of temperature measurement method , or the cooling of the fuse by it's immediate environment - does the fuse board and its lid allow more airflow at one end than the other for example? Or is one set of terminals heavier because it is at one end.

    Depending on the cable type 80C may be not dangerousm but f the fuse is rated 125A, it is running at less than half the rated current, something like a quarter of the rated self heating, it should be running cool.

    How did you verify temperature? I have used thermal labels in the past on parts which overheat when no-one is looking or are not safe to touch.

    If the load is resistive you could swap two phases to the load and see if the problem swaps with them?

    Let us know how you get on.

    Mike

Reply
  • 0

    When you replaced the fuses, did you still see L1 fuse hotter than the other two? If so I'd be looking to see what is different between the phases, either about the detail of temperature measurement method , or the cooling of the fuse by it's immediate environment - does the fuse board and its lid allow more airflow at one end than the other for example? Or is one set of terminals heavier because it is at one end.

    Depending on the cable type 80C may be not dangerousm but f the fuse is rated 125A, it is running at less than half the rated current, something like a quarter of the rated self heating, it should be running cool.

    How did you verify temperature? I have used thermal labels in the past on parts which overheat when no-one is looking or are not safe to touch.

    If the load is resistive you could swap two phases to the load and see if the problem swaps with them?

    Let us know how you get on.

    Mike

Children
  • 0 in reply to mapj1

    Thanks Mr. Mapj1 for your reply. Even after replaced all fuses with new one, still L1 fuse getting high temperature. We are using Infrared thermometer gun for measuring the fuse temperatures. 

    These SFU cabinet doesn't have any forced cooling they just have its environment cooling. Pl refer the picture of SFU cabinet. it will give you more details about its cooling arrangement. 

    Cable type is 1kV 2XCRY, Size is 3x35+16 rm & length is 84 mtr, Revisions A.

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