Fluke 434 Series Ii Application Note 2403043

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Application Note

Lighting is a major load for many large facilities.

Evaluating these circuits is important for both

energy conservation and power quality. Keep in

mind that commercial lighting loads are wired single

phase, with the loads connected from phase to

neutral. Typically, the phase-to-phase voltage is

480 V, with the phase-to-neutral voltage at 277 V.

Measurements must be taken at the lighting panel,

on all phases, since power consumption and Power

Factor could vary on each phase.

1. Power consumption

Excessive phase unbalance can

cause voltage unbalance, which

in turn can affect three-phase

motor loads. For example, in this

three-phase reading, phase A is

considerably higher than B and

C, when all three phases should

be equal.

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

Troubleshooting

commercial

lighting loads

Measurements on commercial lighting loads

Measurement Look for

1. Power consumption (kW) Balance among three phases.

2. Power Factor (DPF and PF) Magnetic ballast will have low DPF. Electronic ballast may have low total PF, although new

generations of ballast often have harmonic mitigation built-in.

3. Total Harmonic Distortion (%THD) Current %THD <20 % is desirable.

4. Voltage Stability Unstable voltage can cause lights to flicker.

2. Power Factor

Ballast with low PF might have

lower cost-of-purchase but

higher cost-of-operation. This

phasor diagram illustrates the

unbalance along with the power

factor.

3. Total Harmonic Distortion

Current THD should be consid-

ered when selecting ballast,

especially if there is a possibility

of transformer overloading. The

bar graph pinpoints the 5th and

7th harmonics as the larger

contributors.

2 Fluke Corporation Troubleshooting commercial lighting loads

The Fluke 43B Power Quality Analyzer trends

voltage (top) and current (bottom) simultane-

ously. Current swells/ inrush caused voltage

sags, indicating that a load downstream from

the measurement point is the cause of the

disturbance.

The Fluke 430 Series Power Quality Analyzers

trend all three phases and compares interac-

tion between the loads.

4. Voltage stability

The sags and swells mode of

power quality analyzers is

especially useful for recording

repetitive voltage sags which can

show up as flickering lights. Both

current and voltage are moni-

tored simultaneously. This helps

us tell if sags are downstream of

the measuring point (load-

related) or upstream (source-

related). For example, if voltage

sags while current swells, a

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For more information call:

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

©2004 Fluke Corporation. All rights reserved.

Printed in U.S.A. 10/2004 2403043 A-US-N Rev A

Fluke. Keeping your world

up and running.

Ø1

Ø2

Ø3

N

Lighting Panel

ABC

277 V Phase-to-Neutral

480 V Phase-to-Phase

Single phase analyzers measure each ballast separately, requiring manual calculations.

Three phase analyzers measure all three phases simultaneously and perform the calcula-

tions automatically.

downstream current inrush likely

caused the sag. If both voltage

and current sag, some event

upstream caused the sags.

It could be an upstream load

like a motor on a parallel branch

circuit which drew down the

feeder voltage. Or it could be

source voltage-related, for

example, a lightning strike or

breaker trip/reclosure on the

utility distribution system.