Anthony wrote:

"john johnson" wrote in
u:



Hi,
I work for a power company, and in one of my earlier roles worked
in the
test section, the section where all the difficult power quality issues
ended up. One that I recall involved a CNC machine shop, the owner was
very angy that we were supplying him with poor quality power and
damaging his machinery. We installed a dranetz power line analyser,
and boy was there some crap in his power systems, it was a wonder
anything worked at all.

The thing is though, we don't supply crap power, well mostly
anyway. By
crap power, I mean power that is still on, but full of dips and
spikes. We do on occasion fail to supply any power, but it's excellent
quality grin We can on occasion, have failures in our voltage
regulation equipment , and supply the wrong voltage, and while low
voltages can cause motors to burn, it's still very rare on our
network. It's also very rare for our equipment to mess up the quality
of the power supply. The only thing we can do to pollute the nice
clean stuff we get from the generators is burning connections, and
they dont usually last very long once they begin to burn. Where 99
percent of the crap comes from is customer loads, either the customer
themselves is doing it, or a close neighbor.



Wholeheartedly agree John....It isn't the power company's fault in our
case, and we know it. It's all the crap we generate in-house. Induction
furnaces, huge 400 hp air compressors (4x), big-assed anodizing
operations (some serious power use there), all the CNC machines, etc.
We pull enough power in our facility to run a small city.



Is your CNC equipment fed directly from the main switchgear where the power
company feeds the facility? If it isn't, you might be plesantly surpirsed
at the improvement you would get by setting up a separate distribution AND
GROUNDING system inside your building just for the CNC equipment; feed it
right off the main power switchgear. Yse larger wire than code requires;
keep the non-CNC equipment on the old feeds.

Another thing you cand try almost for free is to trace the lines from the
CNC equipment all the way back to the main building feed and check that
every connection is properly tightened. Over time this stuff WILL WORK
LOOSE. Several years ago I was in charge of powering a major computing
facility. Every Christmas we shut the whole place down for a day and
tightened connections. We always found one or two 8o(. It is truly amazing
the stunts some industrial electricians will pull; especially with grounds.
Ever see 50 volts of trash between neutral and green on a 120 circuit? It
does WONDERS for networked computers. In this case the ground was connected
to a different transformer than the one feeding the power.
--
Keith Bowers - Thomasville, NC