using power factor 73In researching industrial motors like the
ones used in marine air-conditioning and refrig-
eration systems, I discovered power factor speci-
fications ranging anywhere from 0.57 to 0.95—
quite a spread in what ultimately amounts to the
efficient use of power. But beyond efficiency,
power factor also relates to such important issues
as the amperage-carrying capability of supply
conductors, the susceptibility of equipment to
undesirable voltage drop, and the potential for
heat buildup and insulation damage due to
excessive electrical resistance.
Think of it this way: appliances with low
power factor values will use more power
(wattage), and typically require more amper-
age to function. This means that larger feed
conductors will be needed to supply the
appropriate amperage. Additionally, since
more current must be delivered, undersized
wiring will contribute to potentially excessive
voltage drop. Any AC appliance that is run-
ning continually at lower than specified volt-
age will run hotter than it should, and that
excessive heat can ultimately be the cause for
breakdown of insulation on motor windings
and the like. The bottom line here is that the
longevity of the appliance will be affected and
you are going to be wasting power.
A good resource for motor specifications is
available through the U.S. Department of
Energy at http://www1.eere.energy.gov/industry/
bestpractices/software.html. Once you get to
the site, you will find a free software download
for MotorMaster+ 4.0, which enables you to
compare a large number of motors by per-
formance specification and to calculate and
compare their cost of use over time.Value and Utility
The WattsUp? is not the first tool the
advanced marine electrician or boatowner
should purchase, but it does have utility for
load analysis of AC systems. It won’t work on
high-current-draw items like electric ranges
and ovens, but for refrigeration systems,
microwave ovens, and other commonly used
convenience appliances, it can tell you a lot
about power consumption characteristics.The power factor rating for the more efficient unit, which is plugged
directly into the front of the WattsUp? instrument.