Measuring Three-Phase Ac Voltage - Radio Shack 22-178 Owner's Manual

22-178.fm Page 25 Friday, August 6, 1999 11:38 AM

Measuring Three-Phase AC Voltage

We designed this meter primarily to measure household
AC voltages. It is not intended for commercial or industri-
al use. Please note the following about 3-phase, line-to-
line voltages.
Warnings:
• Because of the dangers inherent in measuring three-
phase circuits, do not use this meter for such applica-
tions. The actual voltage can be greater than the cir-
cuit's rated line-to-ground voltage.
• To determine the line-to-line voltage, multiply the
rated line-to-ground voltage by 1.732 (the square
root of 3).
For example, if the rated line-to-ground voltage is
640 volts, the line-to-line voltage is 640
=1108 Volts AC.
This voltage exceeds the meter's rating and you
should not connect the meter to this circuit.
1.732
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