The motor and phase rotation tester permits the electrical contractor or industrial maintenance electrician to permanently connect and tape the terminals of the motor being installed, without having to first energize the motor by a temporary hookup from a power source, if available, to determine motor rotation. Therefore, the test set eliminates the need for temporary connections that can be time consuming, costly and quite hazardous, particularly where many large, high-voltage motors are involved.
Also, certain types of drives should never be rotated in the wrong direction. In such cases, the temporary hookup or trial method, having a fifty-fifty chance of being wrong, can do serious harm.
The three motor leads on the left side of the test set are for attachment to the terminals of the motor being tested for rotation determination.
Fuses are inserted in the motor A and C test leads as protection in the event the user accidentally touches these leads to an energized circuit. These standard fuses are easily removed and replaced from their panel-mounted holders.
The three lines leading to the right of the test set are for direct attachment to energized ac power systems up to 600 volts to determine the system phase sequence. A four-position switch selects the test to be made – system phase sequence, motor rotation and transformer polarity. The selector switch connects a D-size dry cell into the circuit when the rotation of a motor or the polarity of a transformer is being checked. In the OFF position, both the meter and the battery are disconnected from all circuits.
A push switch is connected in series with the battery and opens the circuit during transformer polarity testing.
The dry cell is easily removed and replaced from its panel-mounted holder by a coin-slot access cap. The dc zero-center ammeter indicates correct or incorrect rotation or polarity by deflecting its pointer to the right or left. A zero or null adjuster is provided for the ammeter.