Bus Plugs Blog – Expert Safety and Usage Information

XLVB321 ITE Bus Plug

Having spent forty years of an Electrical Engineering career in Industrial Research and Development, I feel extremely comfortable in an Electrical Engineering Power Laboratory.  There were few pieces of electrical test equipment that I did not know intimately and use on a regular basis.  Working with 240 and 480 Volt, three phase equipment was quite normal.  And in a Research and Development laboratory, the power wiring was always in a state of flux.  Wiring could be changed minute to minute, hour to hour.  Virtually all power connections were considered transient. 

 So, it came as a surprise when someone used the term “bus plug” to me.  At first, it sounded like somebody from the transit company had an all electric powered school bus, and they had to find a suitable wall outlet to plug into.  Close, but no cigar?   Actually, this wasn’t even close.

Embarrassingly, I had to ask what a bus plug was.   Well, the guru from MIDWEST asked me where did I get my power?  Well, I said, there usually was a distribution network of rectangular gray metal conduits that contained the three phase power busbars that spidered to every lab bench.  I knew these were called bus ducts.  Then the guru asked how did I connect to it?  Well, I said, there are these boxes that attach to the bus ducts.  Each bench’s power comes from these boxes.  Inside, there are usually fuses, and a switch.  The switch usually was just a metal arm with a hole in it that came out of the box.  To turn them on and off, we had long poles with a hook on the end that captured the hole in the arm.  I used these all the time.  Most of the lab benches had these long poles right next to them.  But, the only time I ever saw the interior was when a fuse had been blown inside the box; even then, it was usually a technician’s job to climb up a twelve foot ladder and replace the fuse.  But, a few times, usually at 3 am, I was the one that climbed the ladder.

And the MIDWEST guru said, those boxes are called bus plugs.  Eureka!!!  I’d been using them forever, and just didn’t know what they are named.  It was explained that in order to tap the power from the bus duct conductors, spring loaded fingers touch the internal conductors.  It was also explained that these bus plugs could more or less be snapped onto the bus ducts most anywhere.  

And I said, “Well, now I know exactly what a bus plug is.“