Re: [CAD_CAM_EDM_DRO] Re: LARGE DC MOTOR speed control question

Hi Jon,

One of the more common methods of billing industrial or commercial users
over here (UK) has a three part charge. There is a 'fixed' charge which is
based on the highest KVA used in the past 6 or 12 months (this is measured
as an average over 1/2 hour periods), there is a second part of the charge
which is for the total KVA used in the month, and a third part for the
actual units of electricity used. The difference between the KVA and normal
Kilowatts (Volts x Amps) is the Power Factor which is sometimes also
referred to as 'wattless current' as it represents something you are paying
for but not getting the advantage of. For example, if you have a motor with
a power factor of 0.6, you will pay for 167 KWh of power to get 100 KWh.
Nowadays there are many different ways of paying for power and, just before
I retired a couple of years ago, the power company were trying to persuade
me to buy power by bidding for it the day before! The idea was that, at 3pm
each day, they would provide me with a printed prediction of power costs for
each 15 minute period in the following day and I would tell them how much I
would need and then tailor the building's energy use to suit. Any over use
would result in heavy penalties. Needless to say I resisted strongly - I had
no desire to increase my workload like this overnight!! However, rather than
use tapes, our systems had been hooked up direct to the power company for
monitoring for several years and an actual visit by a power company official
was only an annual event. The power meters recorded all power usage data
every half hour and this was fed both to the power company and to my
building management system so that I could continually monitor usage and
quickly pick up any anomalies. Power factor control was continually adjusted
to the optimum by a big bank of capacitors which were switched in and out in
stages by a controller.

Ian

--
Ian W. Wright
Sheffield UK

----- Original Message -----
From: Jon Elson <jmelson@...>
>
> Now, big energy users DO get charged by power factor and peak usage.
> Our University is charged for an entire year based on the highest usage
> of any 15 minute period within the year. They have a VERY fancy
> electric
> meter, which makes 2 cassette tapes, which are in a sealed and locked
> vault, and are opened every so-and-so period when the tapes are changed,
>
> under the observation of a Univerity official and a power company
> official.
> One tape is for us, one for the power company. There is a correction
> for
> power factor, but I don't know exactly how that is billed.
>