Specifications

112
4.11 — Voltage and Current Unbalance
VOLTAGE UNBALANCE (Maximum 2%)
Voltage unbalance can cause motors to overheat and fail.
Below is the recommended method for determining
voltage unbalance.
Example: Supply voltage is 240-3-60
Average Voltage =
Determine maximum deviation from average voltage:
(AB) 243 – 239 = 4 volts
(BC) 239 – 236 = 3 volts
(AC) 239 – 238 = 1 volt
Maximum deviation is 4 volts.
Determine % voltage unbalance:
% Voltage unbalance = 100 x
= 1.7%
This amount of phase unbalance is satisfactory as it is
below the maximum allowable of 2%.
IMPORTANT: If the supply voltage phase unbalance
is more than 2%, contact your local electric utility
company immediately.
4
239
243 + 236 + 238
3
=
717
3
= 239 volts
AB = 243 volts
BC = 236 volts
AC = 238 volts