Case Studies

ManualsBrandsFluke ManualsDVD Recorder1750

Application Note

Instant power replay

solves a breaker trip

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

After experiencing some nui-

sance tripping of breakers in the

subpanel feeding the second

floor of this industrial building,

we installed a Fluke 1750 Power

Recorder at the subpanel to

gather information about power

usage.

For several weeks, we expe-

rienced no circuit breaker trips,

and the recorded data from the

1750 showed excellent quality

power delivery.

The next week, using the cur-

rent event detector with a 20

A threshold to match the single

phase branch feeds, we dis-

covered that there were several

events where current exceeded

the breaker trip rating. While

there were no tripped breakers

during the week, it was clear

that something was overloading

the circuit to the point where a

breaker trip was likely to happen.

A search of the facility found

an employee who had moved

a Tenny temperature chamber

into a lab area and was using

it to perform elevated tempera-

ture tests on some products. The

Figure 1. Current event view, top level events

chamber was on wheels and

was plugged into a standard

120 V, 20 A branch outlet.

The power recorder captured

the operation of the temperature

chamber and its effect on the

power at the sub-panel.

Data analysis

The current event view shows

several events outside the 20 A

breaker tolerance curve. The lon-

gest event is shown in Figure 1.

The event exhibits a double

initial current surge, followed

by a sustained current over

20 amps. Although the circuit

breaker did not trip during this

event, its rating was exceeded

and it would be likely to trip

occasionally under similar con-

ditions. These conditions are

frequent during use of the tem-

perature chamber, as can be

seen in the graph above, where

this event is immediately fol-

lowed by another similar event

whose beginning can be seen at

the right side.

Testing Functions

Case Study

Operator: Michael Gipe, Fluke Power

Electronics Engineer

Measuring tools: Fluke 1750 Power

Recorder

Tests conducted: Power quality

event recording

Summary of content (2 pages)

PAGE 1
Instant power replay solves a breaker trip Testing Functions Case Study Measuring tools: Fluke 1750 Power Recorder Application Note After experiencing some nuisance tripping of breakers in the subpanel feeding the second floor of this industrial building, we installed a Fluke 1750 Power Recorder at the subpanel to gather information about power usage. For several weeks, we experienced no circuit breaker trips, and the recorded data from the 1750 showed excellent quality power delivery.
PAGE 2
Zooming into the initial region of the event in Figure 2, we see the turn-on loads of the temperature chamber’s dual compressor system. The first compressor turns on with a large initial surge, followed by the secondary compressor surge. This load profile clearly identifies the temperature chamber as the cause of the overload. Temperature chamber peak current is 49.7 amps. In Figure 3, the sustained load is near 25 amps.