Bus Plugs Blog – Expert Safety and Usage Information

Buy Square D PQ3640 Bus Plugs

All too often our little friend the bus plug ends up making the ultimate sacrifice resulting in a catastrophic failure in the line of duty.

Not long ago we got a call from a customer asking for a bus plug replacement for one of theirs which failed in service. The circumstances surrounding the bus plug failure cannot be discerned.

The bus plug involved was a Square D PQ3640 (3 phase, fusible, 600 volts, 400 amps), the older version of the Square D PBQ style bus plug. One can only speculate as to what happened exactly, but the evidence told of a frightening scenario. A hole the size of an orange was burned completely through the bus plug cover. The inside guts burned beyond recognition, copper splattering along with carbon residue scattered throughout the inside of the bus plug.

Oddly enough the extent of the damage was confined to the bus plug itself and did not affect the bus duct proper. As mentioned many times before, bus plugs often operate under highly stressed conditions seriously compromising their life in service.

MIDWEST General Bus Plug Information, Uncategorized bus plug, square d bus plugs, square d pq3640

Our Switchgear Shop claims nothing surprises them anymore.  Well they got a surprise last week.  We received a 400 amp, old bus plug for reconditioning.  It looked in great condition, almost like a new bus plug. The receiving inspection read something like, Good, Good, Good, on and on, and at the end, Junk.  It seems the reason the customer sent in this bus plug was because it looked like the Titanic.  It had an 18 inch slice along one side of the enclosure.  Very clean, very deep and perfectly straight.  We have no clue how they did this.  But we suspect a fork truck was involved. MIDWEST gets a few old bus plugs that have lost a battle with a fork truck. So our guys took a picture and added this one to our “Wall of Horror.”

MIDWEST General Bus Plug Information bus plug, damaged enclosure, great condition but junk