ABSTRACT
In three-phase installations it is important to ensure that phase sequence is maintained from the origin through to the connection points for any three-phase current using equipment. Many items of three-phase equipment will not operate correctly if the phase sequence is wrong and this can give rise to danger. This is especially true for many three-phase motors, where reversing the phase sequence will cause the motor to rotate in the opposite direction. Verifying correct phase sequence is a very similar process to confirming correct polarity, so first one must confirm by visual inspection that L1, L2 and L3 are correctly identified and terminated at the origin. There are two types of phase rotation tester: rotating disc type, which uses a small three-phase motor and gearing to rotate a disc clockwise or anti-clockwise depending on phase sequence and indicator lamp type, which uses electronic circuitry to check the phase sequence and then illuminate a lamp for clockwise or anti-clockwise.
