Tell the Germans back in the 70's. Maybe they weren't invented yet.

We had the electrician (we is loose - county school I live in county)
wire up a very large and powerful CNC umpteen axis machine and blew up
the campus transformer! That is a big transformer for a college.

Took two days to get one installed. Department head was axed. Had to
do it to someone. (He was a friend).

A meter would have detected the shorting neutral/gnd to a hot and a hot
to a neutral ground.

Lots of stuff had to be replaced on the new monster mill. The regional
companies that supported the class - feeding them programmers and users
They stepped up and paid for the burnt motors and such.

The electrician for the school, a Master, blew it and others caught it.

I think to boot it, the voltage was from the wrong panel and was the
wrong voltage as well.

I worked in a R&D lab with large machines and we had 50, 60 and 400 Hz
power buses. The 50 and 400 was generated on site. You can bet we had
stuff labled and checked it when a bus wasn't being used.

Martin

On 1/15/2016 2:50 PM, Ignoramus475 wrote:
On 2016-01-15, Martin Eastburn wrote:
I had students with a Can manufacturing company that got a big
machine that was 3-phase all over it. the motors had to start
in the correct direction the first time. I seem to recall something
like gear train destruction would occur. I luckly found a Neon lamp
tester in a magazine that fit the bill. This was in the early 70's.

Such things should be protected by "three phase rotation relays".

i