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
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.