A special note: Although the needle will swing in the opposite direction after the shaft stops turning, you should use the voltmeter's first indication as to the status of rotation direction. Finally, you hand-turn the motor's shaft in the desired direction while watching the voltmeter, which immediately will swing to the CORRECT or INCORRECT direction.
Then you position the meter's selector switch to "MOTOR" and connect the three MOTOR leads to the motor's leads. Three leads, labeled "A," "B," and "C," are connected to the test unit's side labeled "MOTOR." Three other leads are labeled the same but are connected to the test unit's other side, which is labeled "LINE." The meter also has a zero-center voltmeter, with one side labeled "INCORRECT" and the other labeled "CORRECT."įirst, you "zero" the meter per the manufacturer's instructions.
There's another option, one that's less time consuming and more efficient.Ī phase rotation meter, through the use of its six terminal leads, compares the phase rotation of two different 3-phase connections. And, after making the lead interchange, if required, the motor then can be coupled to its load. We can temporarily power the motor while it's uncoupled from its load and observe its direction of rotation. If it's the wrong direction, we can simply interchange any two line leads.īut what can we do if the connected load would be damaged with the motor's reverse rotation? We have to determine the correct rotation before the motor is connected to its load. If we know that the connected load will not be affected by the motor's reverse rotation, we can temporarily power the motor and observe its direction of rotation. This interchanging, if you will, reverses the direction of the rotating magnetic field within the motor. We all know that the direction of rotation of a 3-phase motor can be changed by reversing two of its stator leads. What critical task must be performed for the correct operation of the motor's connected load? That's right: Determining the motor's correct rotation. You've just had a motor repaired or purchased a replacement, and you're about to connect it.
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