5.4.1 Using Option X-21
Perhaps the easiest and most common method of making connections to the Power Analyzer is
through the use of the Option X21 Load Power Cable. Option X21 allows for quick and easy
connection of any device that uses a standard AC plug. Connections using Option X21 are
shown in Figure 5-2.
Figure 5-2 | 2105 Connections using the X-21
5.4.2 Using CT’s and PT’s
Current and potential transformers (CT's and PT's) may be used with any Valhalla Digital Power
Analyzer to increase its measurement range. Clamp-on CT's may also be used to simplify power
analyzer connections.
5.4.2.1
Current Transformers
Current transformers (CT's) are used to extend the current measurement capabilities of Valhalla
digital power analyzers. CT's are available in many ratios, maximum current ratings and
isolation voltages.
There are two styles of CT's available, fixed and clamp-on. Fixed CT's are generally used for
permanent test set-ups. The conductor being measured must be disconnected, passed through
the center of the CT, and reconnected. Clamp-on CT's are easier to use because they are just
clamped around the conductor. The conductor need not be disconnected when using a clamp-
on CT.
CT's are also used for isolating the power analyzer from high voltage systems. Many high
voltage systems operate at current levels directly measurable by the power analyzer, but with
voltages beyond the power analyzer limits. The isolation voltage rating should be at least 1 ½
times the peak input voltage.
When selecting a CT, try to use decade ratios e.g. 10:1, 100:1, etc. Decade ratios make for
easier power analyzer measurements. The user just mentally moves the current and power
display decimal points to the right the appropriate number of places. Valhalla offers three
types of CT's which are listed in Section 4 of this manual. Of course, non-decade ratios may also
be used. The maximum current rating of the CT should be selected 1 ½ times the expected
current to allow for high crest-factor waveforms.
The ratio accuracy of CT's is usually about 2%. This is quite a bit wider than the accuracy of a
digital power analyzer. The easiest way to improve this accuracy is to measure the actual ratio
and use this value when correcting measurements.
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