K
Ken Taylor
- Jan 1, 1970
- 0
Rene Tschaggelar said:Only once in a lifetime you can possibly experience half
a foot of 1mm^2 evaporate. With just an hour left to do
a final spectrum measurement, we threw a bunch of cables,
filters, coupling capacitors, connectors and screw
blocks, stepdown transformer into a shoebox and plugged
the 100Amp connector into the isolated system with a
generator then delivering 3x460V @ 2000A just a few
meters away. My makeshift wiring must have had a
fault, it took a noticeable delay after flipping
the switch until the wire evaporated with a thunder.
Strange enough, the plastic insulation stayed there,
perforated, just the copper was missing but the
surrounding cables and cases were copper covered.
No question was asked why they had to put a main
breaker back in ... oops.
Rene
Back in my training days we were working on an old ship's gunnery radar. It
was running of 3-phase (415V), and had an OFF/Standby/On (from memory) main
power switch. Off was, well, off, standby was still off but had the 3-phase
input to the power supply shorted out and on was exactly that. This switch
remotely operated the contactors in the power distribution room. One day I
was working with a colleague and we decide we were finished so switched
off - we got to 'standby' and thought "Hang on, one more measurement...." so
switched back on. Nothing powered up. Hmmmm. Went inside the main building
to check the breakers to see another training group standing stunned outside
the power room.
When we switched rapidly On/Standby/On the contactor made-before-break and
vaporized a large part of the switchboard, which was deposited as a film
around that room which was thankfully vacant at the time (but caused various
people outside it to soil themselves!). There had been two problems - a
break-before-make contactor was changed, and the replacement was mounted
vertically instead of horizontally as specified.
Ken