FINE INSTRUMENTS CORPORATION FINEST 135, User Manual

power line current for only a 

 of 

 cycle so that

they 

 non-linear loading and subsequent non-linear

current 

 This generates odd harmonics of the 

line frequency. Therefore, the current in the transformer of
today contains not only a 

 (or 

 component, but a

 (or 

 component, a 

 (or 

ponent, and the other 

 harmonic components up

to a 

 (or 

 component and beyond.

The 

 addition in a 

 power distribution

 non-linear loads may still be quite low. But,

the addition does not cancel all the harmonic currents. The
odd multiples of the 3rd harmonic (called the 
are, 

 added together in the neutral. These

harmonics 

 form a total rms current in the transformer’s

neutral wire that is normally 130% of the total rms current
measured in any individual 

 whose theoretical 

 is 173%. For example, 

 currents of 80 amperes

may 

 harmonic current flow in the neutral of 104

amperes. The dominant current flow in the neutral is most
commonly the 3rd harmonic.

The electrical 

 must consider the following

3 issues when he designs a power distribution 
containing harmonic current flow.

1.

2.

The AC neutral 

 must be of suff icient gauge   

for harmonic current flow.

The distribution transformer must have additional 
to continue Operation at its rated 

 if it is not

 This   

 the harmonic current flow

in the secondary neutral wire   circulating in the 
connected 

 winding, after it   

 to the

primary winding. The circulating harmonic current heats

 the transformer.

Phase current harmonics are reflected to the 

winding and they continue back towards the power

 This 

 distortion of the voltage wave so

that any power 

 correction capacitors on the line 

be easily overloaded.

We 

 use this Meter to analyze components such as power

distribution transformers and power 

 correction

capacitors.

6.2 General Applications

You 

 conductor carrying AC unless this

conductor is at a potential above 600V AC or at a frequency
above 

 True rms measurement yields the 

current value.

Press the ON OFF pushbutton to turn on this Meter.

Clamp around the conductor to be measured. Be sure the

 jaws are securely closed, or measurements will not

be accurate.

Observe the display for true rms current flow.

Press the Hz pushbutton to measure frequency.

Press the HOLD pushbutton   freeze the digital display,
if