Fuse Maintenance, Part 2

A good fuse maintenance procedure has two parts

A good fuse maintenance procedure has two parts:

  1. Maintenance while energized:
    • Infrared scans of all connections, especially fuse clips.
    • Voltage checks across fuses (not necessarily right at the fuse).
  2. Maintenance while de-energized:
    • Insulation resistance tests of wiring and fuse holders.
    • Resistance measurements through connections and fuses. For control fuses, you can use a DMM. For power fuses, use an appropriate AC resistance tester.
Both parts include visual inspection for corrosion, discoloration, or deterioration.

If resistance measurements identify high resistance connections, fix the connections. For each one, disassemble, clean, reassemble with new fasteners, and tighten to the specified torque.

One thing a good fuse PM won't include is "tightening of connections." Though this practice is often advised, it is always ill-advised. Once a properly made connection becomes loose (for whatever reason), you can’t restore the clamping power it previously had. In fact, "tightening" reduces clamping power by stretching the fastener past its elastic limit. To restore the connection, you must replace the hardware.

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