3. VARIDRIVE PREPARATION. Before starting any tests the varidrive assembly
should be operated over the entire range. This provides a functional check to
determine operational status.
a. Protruding through the high voltage panel there is a main circuit
breaker switch that makes three-phase power available to the whole test stand.
This panel can be seen in figure 1 next to the work lamp. Also, behind this panel
is the varidrive reversing switch, which is a large dual knife switch to the left
of the main circuit breaker. These components can be seen in figure 2.
the ON position. This is indicated by the illumination of the "Power On" lamp.
The high voltage compartment door must be tightly closed or the interlock switch
(fig 2) will be open. If the interlock is open, it will prevent the varidrive
assembly from operating.
c. To start the varidrive, depress the START button (28, foldout 5) on the
control panel. The button must be held down until the blower motor comes up to
speed. This will happen in Just a few seconds. Once air is flowing through the
load bank and the rectifier compartment, the flow sensing switch (S5) will close.
Then the magnetic motor starter, which is a large relay, will lock itself up
through a 50-ohm resistor at reduced current and remain energized. This will keep
the three-phase power applied to the varidrive through the contacts of the magnetic
(1) If for some reason there is no airflow for cooling, the varidrive
unit will not remain in operation, indicating a malfunction.
(2) Holding the START button closed in excess of 30 seconds will cause
the magnetic motor starter to overheat and damage the starter coil.
REPEATED USE OF THE MAGNETIC MOTOR STARTER AT FREQUENT SHORT INTERVALS MAY
DAMAGE THE STARTER COIL AND CONTACTS BY OVERHEATING.
(3) Once the varidrive assembly has started, operate it over the entire
range of 1,830 to 11,000 RPM by turning the drive speed control (42, foldout 5)
clockwise and then counterclockwise.
To reverse the direction of rotation, the varidrive must be completely
HIGH VOLTAGE EXISTS IN THE HIGH VOLTAGE COMPARTMENT. BEFORE OPENING THE
COMPARTMENT DOOR, PLACE THE MAIN CIRCUIT BREAKER IN THE OFF POSITION.
(1) Depress the STOP button to stop the varidrive assembly.
(2) Snap the main circuit breaker to the OFF position.
(3) Place the varidrive reversing switch (fig 2) into the opposite
4. TESTING CONSIDERATIONS. In preparing the 500-ampere test stand for
operation, one must consider the unit under test (UUT) and its installation on the
test stand. The UUT's are generators, alternators, regulators, rectifiers, and
starters. Our concern here is with generators, alternators, and regulators.
OS 010, 4-P3