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Application Note

Basic power quality

measurements on the

go with the Fluke 345

Waveform view

The world runs on ac voltage, be it at

home, shopping center, hospital, factory,

or industrial complex. Sometimes valuable

troubleshooting information can be

gained by “viewing” the ac waveforms

behind the action. Turn the Fluke 345

switch to Waveform mode and you

can view the voltage and current

waveforms. From there, select either of

the waveforms and use the arrow keys

to measure voltage at a specific point

on the waveform, as well as the time

between two points on the waveform.

The Fluke 345 combines a clamp meter,

power quality meter, oscilloscope, and

data logger in one. This combination of

functions, coupled with high quality

digital filtering, makes it ideal for working

with variable frequency motor drives,

high efficiency lighting, and other loads

using switching electronics.

The basics

Of course, the Fluke 345 will make the

basic measurements of voltage and cur-

rent to determine if there is something

seriously wrong with the circuit under

test. It is rated for use at the service

entrance with a 600 Volt CAT IV rating.

Measuring voltage is as simple as

using a clamp meter: Connect the test

leads up to the voltage inputs, select

voltage, and then read the rms voltage.

Current measurement is just as easy.

Select current, open the jaw, clamp

around the wire, and measure. With

the 2000 A range and large jaw

opening, you can evaluate most of

the circuits in the building.

The Fluke 345 can also measure

both ac and dc voltage and current

simultaneously, and identify the

magnitude of each separately and

combined as ac+dc true-rms. That is

helpful for checking a UPS, battery,

and output, to make sure that the

circuits are working correctly and the

batteries are in good condition. A dc

voltage component on the output of a

UPS, or even an adjustable frequency

motor drive, may even be a quick

indicator of a developing problem. For

example, waveform non-symmetry will

cause an apparent dc voltage component

and may indicate impending failure of

system output electronics.

During your day-to-day measurement activities, there may be

situations where you need to know more than what voltage

or current is present. When that happens, the standard clamp

meter is not going to get the job done. The solution may be a

power quality clamp meter such as the Fluke 345.

Figure 1. The dual waveform display on the

Fluke 345 shows both voltage and current waveforms.

Summary of content (4 pages)

PAGE 1
Basic power quality measurements on the go with the Fluke 345 Application Note During your day-to-day measurement activities, there may be situations where you need to know more than what voltage or current is present. When that happens, the standard clamp meter is not going to get the job done. The solution may be a power quality clamp meter such as the Fluke 345. The Fluke 345 combines a clamp meter, power quality meter, oscilloscope, and data logger in one.
PAGE 2
Armed with the waveform and harmonics data, you have a good chance of understanding why the electrical system, and the equipment connected to it, are behaving the way they are. For example, if the voltage waveform is flattened on top, you may find some equipment will reset or operate erratically, because its electronic power supplies are not functioning properly. If the current is drawn in short pulses instead of a sine wave, it’s likely that you have an electronic load and potential harmonics problems.
PAGE 3
Inrush current Sometimes, after performing a power test, the circuit breaker will still open when a load starts up. Usually, that means there is a momentary current surge, called inrush. When that happens, use the Fluke 345 to measure the peak value and duration of the inrush current during load start. With that information, you can determine whether to move the load to another circuit or make other appropriate changes to the existing circuit.
PAGE 4
Fluke. Keeping your world up and running. TM 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) 446-5116 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 Fluke (UK) Ltd.