>-----Original Message-----
>From: Doug McKean [mailto:dmck...@corp.auspex.com]
>Sent: Friday, May 11, 2001 5:39 PM
>To: emc-p...@ieee.org
>Subject: Re: Voltage vs. Power
>
>
>
>"Ken Javor" wrote:
>>
>> I wasn't going to weigh in on this, but here goes. For residential
>and
>> commercial non-industrial use, heating and air-conditioning must
>consume the
>> most power. Since these are feedback controlled systems, lowering
>power
>> consumption by reducing line voltage would only increase the amount
>of time
>> the heater/ac system was "on." Am I missing something?
>
>I hope some people are still reading this thread.
>
>Interesting. I took a 120vac/60Hz fan in the lab and tested
>it to see what effects I'd get lo-lining a synchronous device.
>I'm using a Pacific SmartSource 360-AMX AC power
>source which gives me several readouts.
>
>Input KVA KW PF Amps Amps
> vac RMS Peak
>
>125 0.049 0.051 0.979 0.413 0.650
>120 0.046 0.048 0.978 0.409 0.625
>115 0.042 0.045 0.976 0.393 0.600
>110 0.039 0.041 0.976 0.381 0.625
>108 0.041 0.040 0.978 0.372 0.575
>105 0.039 0.038 0.975 0.366 0.600
>100 0.036 0.035 0.975 0.350 0.575
>
>A 5% reduction from 120vac to 115vac (if you're willing to
>accept 115 being approx. 114) yields the following changes ...
>
> KVA -8.70%
> KW -6.25%
> PF -0.20%
> AMPS RMS -3.91%
> AMPS PEAK -4.00%
>
>A 10% reduction from 120vac to 108vac yields the following
>changes ...
>
> KVA -10.9%
> KW -16.7%
> PF 0.0%
> AMPS RMS -9.0%
> AMPS PEAK -8.0%
>
>So, the other concern I have is the regular variation of the public
>mains. The grid must vary and I don't have any information how
>much it varies during the course of, what, a week, month, year?
>If the line was reduced to 108vac, what would be the anticipated
>low line during normal operation?
>
>- Doug McKean
>
>
>
I too, didn't want to jump into this, but Doug's data prompts me to add one
point.
We use electrical energy mainly in two residential ways. First, there are
"informational" (lacking any better word) uses, such as operating a
television, clock or doorbell transformer. These loads may use a bit less
power if the voltage is reduced. I called them "informational", since they
convey information rather than perform work.
The second group are "working" devices. These devices transform electrical
energy into physical work. Examples of these are heating water, pumping
water, compressing gas, lifting mass, blowing air and creating light. In all
of these cases, we are modifying the state of matter by applying energy. As
an example, if we want to move 500 gallons of water (about 3000 pounds) to a
tank 100 feet above ground, we need to apply 300K foot-pounds of energy to
do it (neglecting all the little losses). That 300K ft-lbs (about 0.1 kWHr)
must be expended to do the job. If the voltage supply is reduced, the pump
motor may draw less power, but it will then do less mechanical work in a
unit of time. You still need to expend the same amount of energy; it just
takes longer to complete the work.
Regards,
Ed
Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Services Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
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