ALL-TEST PRO AT31 - Phase Balance Test; Test Purpose and Calculator; Phase Balance Test Procedure - Steps 1-2

ALL-TEST PRO
®
31 User Manual
©2011, ALL-TEST Pro, LLC www.alltestpro.com rev 2011-11F 17
Phase Balance Test
This calculates the impedance unbalance between phases. This value can be used to relate energy,
reliability and production-cost avoidance potential to electric motor systems impedance unbalance. The
Impedance Unbalance Calculator (IUC) is available from ALL-TEST Pro. The concept of the IUC
comes from Keeping the Spark in Your Electrical System: An Industrial Electrical Distribution
Maintenance Guidebook published by the US Department of Energy, Bonneville Power Administration,
Pacific Gas & Electric, PacifiCorp and Tacoma Public Utilities. As impedance varies with each phase,
the current in each leg of the motor varies. This generates increased losses in the form of heat. Heat
reduces both insulation life and the life of the lubricant.
(The Impedance Unbalance Calculator is available from ALL-TEST Pro).
1. Place the Test leads on any 2 motor leads, for discussion purposes use T1 & T3.
2. Press the ZERO key to set the reference phase to zero. This establishes (T1-T3) as the reference
phase.