🚀 go-pugleaf

Phil Allison wrote:
> "Stupider than Anyone  Else"
> 
>> I have to phases of power supply to my house - so three power lines, two 
>> phases plus neutral.
>>
>> I've on occasion wondered what would happen if we lost the neutral line. 
>> It seems to me that we'd then have the voltage between the two phases 
>> across two sets of appliances, one set attached to one phase, and the 
>> other set attached to the other phase, with the two sets in series as a 
>> result of their common connection to the neutral wire. Since the two sets 
>> are unlikely to represent equal loads, the net result would be a large 
>> overvoltage on one set of appliances.
>>
>> My electrician says it's not an issue, but I can't see why.
> 
> 
> ** Loss of the neutral conductor in a 3 phase ( or 2 phase) AC supply system 
> can easily be a DISASTROUS  event.
> 
> For example:
> 
> In the live entertainment productions -  high powered lighting and sound 
> systems operate from 3 phase outlets via a hefty 5 pin plug and socket.  If, 
> due to wear and tear or damage to the plug or socket, one of the phases 
> drops out  -  that is an annoyance but not a disaster.
> 
> However, if the pin carrying the neutral fails to connect or as is often the 
> case *disconnects* during a show because of overheating   -  ALL HELL 
> BREAKS  LOOSE !!
> 
> Typically, some of the lamps will glow very brightly for a second or two and 
> fail, then other previously dim lamps will follow suit.  The AC fuses in 
> amplifiers will pop instantly and some equipment will be seriously damaged 
> when the PSU sections are destroyed. It all happens in a few seconds, while 
> the operators stand there with their mouths open  !!!
> 
>
> 
> 
> ....  Phil
> 
> 
> 
> 
I recently had such an event happen at a theater. It was county fair 
season and the vendor was scrapping the bottom of the barrel for gear.
It was an old distro, with a Yamaha 3500 FOH, with an effects racks.

About 2 hours before house, everything was working when i heard the 
system crackling. I looked over at FOH and the lights were flashing.
Then smoke started coming out of the effects rack. I ran to the stage
to shut off power amps and shut everything down.

It was split phase going to FOH. Measured 220 between the hots, and 
nothing to neutral. Somewhere, the neutral was lost. Checked the 
connector on stage and changed the plugged slot on the distro.

At that point, power came back the way it should. BUT, the effects rack
was still smoking due to fried MOV's in the Furman plug strip.
And all the Drawmer compressors were DOA. luckily, the Yamaha console
was ok. Did the show with a few less toys.

bob