Making Watt Hour Measurements With Fluke Power Quality Analyzers

Making watt-hour
measurements
with Fluke power
quality analyzers
Introduction
The need to manage power is
never more critical than when
power prices skyrocket and
power quality becomes suspect.
Electrical technicians today are
more aware of power consumption and are on the watch for
consumption that’s higher than
anticipated. Once that occurs,
technicians must become detectives andtry to trace the power
consumption back to its source.
Fluke single and three phase
power quality analyzers are
excellent tools for conducting the
portable energy audits necessary
to track down energy draining
devices.
This application note details
the procedures for using Fluke
power quality analyzers for
average watt measurements and
converting those to watt-hours.

Average wattageto
watt-hours conversion
Fluke power quality analyzers
can provide a reading of average
wattage over time, a value that
can be easily used to determine
watt-hours. To convert average
watts to watt-hours, simply multiply the average watts reading
by the amount of time over which
the average was measured.
For example, the following
calculations are for continuous
loads (for cyclingloads, see load
cycle considerations):
• A one-watt averaged load
measured for one hour is equal
to one watt-hour; a 1000-watt
averaged load measured for
one hour is equal to one kilowatt-hour.
• A 60-watt averaged load
measured for two hours is
equal to 120 watt-hours.

Application Note

•

A 60-watt averaged load
measured for 15 minutes
(one-quarter hour) is equal to
15 watt-hours.This technique for measuring
real power consumption (kWh)
can also be applied to apparent
power (kVA) and reactive power
(kVAR). Simply set the power
quality analyzer to calculate the
running average kVA or kVAR,
then multiply by the recording
time to get kVAh or kVARh used
by the load.

Load cycle
considerations
When making average watt
measurements, be sure to take
intoconsideration the load cycles
you’re working with.
Long cycle loads: If the load
creating the watt draw has a
long on/off cycle, like a refrigerator, be sure to measure long
enough to include several on/off
cycles to get a good representation of the average watts. If possible, try to stop the
measurement at an even number
of on/off cycles to reduce measurement errors.
Short cycle loads: If loadscan cycle on and off or make
large changes faster than one
per minute, use an advanced
three phase analyzer to ensure
the wattage valves are captured.

Using the Fluke 43B Power Quality Analyzer for average
watt measurements.

Making average watt
measurements with the
Fluke 430 Series
On the three phase 430 power
quality analyzers, the energy
function automatically measures
andcalculates Watts/VA/VARs.
Simply connect the clamps and
leads and select energy from the
menu.

From the Fluke Digital Library @ www.fluke.com/library

Fluke 43B recording mode with record time
selections from four min to endless (16 days).

Using the Fluke 43B
for average watt
measurements
1. Connect the 43B.
2. Connect the voltage leads
and current clamp before
starting the recordmode.
3. Select the power mode and
make sure the wattage readings are correct.

4. Press the record button and
select watts for reading #1.
Reading #2 is not required,
so you may select any of the
other items — VA (volt
amperes) would be a good
choice for reading #2 unless
you have some other need.
5. Selecting record time:
• If you do not know how
long you are going to be
making thewatt average
measurements, then use
endless which has a 16-day
maximum. Be sure to keep
an accurate record of how
long the measurement was
made; longer is better to
keep timing errors to a
minimum.
• If you know how long you
want to measure, then
select one of the preset
times (four minutes to eight
days). Use that time value to
calculate the watt-hours
unless you stop 43B record...