Re: [MV] Electrical question

From: INDUSTELE@aol.com
Date: Sun Oct 15 2000 - 15:46:01 PDT


Sorry to be late on my 2 cents worth on this. I was out in the bushes
playing like a Boy Scout over the weekend, just got back in and saw the
thread about the power.

Three phase power is calculated as Power (P) = (Square Root 3) x (Voltage) x
(Amps). The comment about start up power on a compressor is right on the
nose. Starting current of compressors or pumps can be 500% to 600% higher
than the operating voltages. This is usually handled by the breaker settings
(factory or otherwise) that will allow over current for a few milli-seconds
before tripping.

In this case for the air conditioner only the figures would be:

Power (in watts) = 1.732 x 208volts x 28.5 amps or 10,267.296 watts MINIMUM
requirement.

The lights need to be figured as 100 watts each, counting the ballast lost,
or a total of 800 watts, for a grand total of 11,067 watts. You can then
figure in all the other "extras" you are wanting to add (if any). As a bare
MINIMUM you will need a 11,000 watt or 11KW generator. Since this is an odd
ball size go to at least a 12,000 watt unit.

Be careful, some of the ads in the discount places advertise 10,000 watt but
then in the small print they say that this is the "surge" wattage, but the
operating wattage is something like 8,500 range. Be sure you are looking at
a 12,000 watt OPERATING range generator.

Also be aware that this will generally be a fairly large generator. You may
want to consider a belt driven generator that is run off of the main engine,
but that (of course) would require running the main engine all the time.

Contact me off list if you would like any additional information.

Tom Campbell - Birmingham, Alabama
(old Olive Drab junk collector and Master Electrician in all southeastern
states)



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