Fluke 43B Application Note 2066287 Rev A

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Application Note

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 consump-

tion and are on the watch for

consumption that’s higher than

anticipated. Once that occurs,

technicians must become detec-

tives and try 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 wattage to

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 mul-

tiply 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 cycling loads, 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 kilo-

watt-hour.

•A 60-watt averaged load

measured for two hours is

equal to 120 watt-hours.

•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

into consideration 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 refrigera-

tor, be sure to measure long

enough to include several on/off

cycles to get a good representa-

tion of the average watts. If pos-

sible, try to stop the

measurement at an even number

of on/off cycles to reduce meas-

urement errors.

Short cycle loads: If loads

can 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.

Making average watt

measurements with the

Fluke 430 Series

On the three phase 430 power

quality analyzers, the energy

function automatically measures

and calculates Watts/VA/VARs.

Simply connect the clamps and

leads and select energy from the

menu

.

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

Making watt-hour

measurements

with Fluke power

quality analyzers

Using the Fluke 43B Power Quality Analyzer for average

watt measurements.

2 Fluke Corporation Making watt-hour measurements with Fluke power quality analyzers

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 the watt 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

mode before it stops itself.

In that case, record the

measurement time at which

you stopped the recording.

6. Start the recording.

7. Press the hold button to stop

recording unless you are going

to let it automatically

stop on

one of its preset values.

8. Before turning off the 43B or

disconnecting the voltage

leads and the current clamp,

write down the average watt

values or save the screen

information in one of the save

memories.

9. Convert watts to watt-hours as

described on page 1.

Fluke 43B recording mode with record time

selections from four min to endless (16 days).

Glossary

Apparent Power In an ac circuit, the power value obtained by multiplying the current by

(kVA) voltage (P equals IE), with no consideration of the effects of phase angle.

Kilowatt 1,000 watts

Reactance The opposition offered to the flow of alternating current by

(X) pure capacitance, inductance, or a combination of the two.

Reactive Power The product of kilovolts and amperes in a reactive component of a circuit.

(kVAR)

Real Power The apparent power multiplied by the power factor in an alternating-current circuit

(kWh) containing reactance. Real power is the difference between the apparent power and

the reactive power. Actual radiated or dissipated power cannot exceed real power.

Watt-hour A unit of electrical energy or work. It is defined as one watt of power sustained for

(WH) one hour. A 13-watt lamp operating for 6 hours would consume (13 W) x (6 hrs) = 78 WH.

A larger unit of measurement is the kilowatt-hour (kwh), which is 1000 WH.

For accurate measurement of short cycle loads, use a power recorder with high resolution capabilities.

Using the Fluke 43B

for average watt

measurements

1. Connect the 43B.

2. Connect the voltage leads

and current clamp before

starting the record mode.

3. Select the power mode and

make sure the wattage read-

ings are correct.

Fluke Corporation

PO Box 9090, Everett, WA USA 98206

Fluke Europe B.V.

PO Box 1186, 5602 BD

Eindhoven, The Netherlands

For more information call:

In the U.S.A. (800) 443-5853 or

Fax (425) 446-51

16

In Europe/M-East/Africa (31 40) 2 675 200 or

Fax (31 40) 2 675 222

In Canada (800) 36-FLUKE or

Fax (905) 890-6866

From other countries +1 (425) 446-5500 or

Fax +1 (425) 446-5116

Web access: http://www.fluke.com

©2004 Fluke Corporation. All rights reserved.

Printed in U.S.A. 10/2004 2066287 A-US-N Rev B

Fluke. Keeping your world

up and running.