Figure 10.
DC ammeter.
g. What you have learned about basic DC voltmeters and ammeters apply
directly to five of the seven test stand metering circuits (fig 11). M1 through M5
on the schematic are representations of meter movements similar to the one
discussed. Organizational maintenance personnel should be able to state the
probable cause of a malfunction in meter circuits M1 through M5. Supervisors
should check to insure that the reporting of malfunctions is as specific as
possible. Specific reporting of malfunctions will help the repairman to quickly
return the equipment to a serviceable condition.
8.
ELECTRICAL WIRING DIAGRAM ANALYSIS (FIGURE 11).
a. Organizational maintenance personnel should be able to analyze the 500-
ampere test stand electrical wiring diagram. You, as a supervisor, must be able to
determine their ability to perform that task. An analysis of the 24VDC battery
charging function of the test stand is included in this lesson. After reading this
analysis you will know what should be expected from organizational maintenance
personnel analyzing any function of the test stand.
b. AC power input to the test stand is converted to DC power and used for
24VDC battery charging. One phase of the AC input is applied to the primary of
transformer T1 from the L1-L3 input. Closing CB1 completes the circuit from L1
through the knife switch to the right side of the T1 primary and completes the
circuit from L3 to the left side of the T1 primary. The AC power coupled to the T1
secondary powers the 0-32VDC supply, 0-28VDC supply, and 28VDC supply. When CB1 is
closed DS1 will illuminate, indicating that AC power has been applied to this part
of the circuit.
c. AC power is connected from the secondary of T1 to the primary of T6 when
CB6 is closed. AC power coupled to the secondary of T6 is rectified by bridge
rectifier CR3. The 28VDC rectified output, existing between wires P56 and P49,
energizes several relays if CB7 is closed. S20, the battery voltage selector,
would be in the 24V position for 24VDC battery charging. Therefore, the K7 relay
would be energized and DS7 would illuminate. The ground polarity switch should be
in the (-) position, thus energizing relay K9. The regulator load resistor
selector (S24) is set to OFF, which allows K11 to energize.
OS 010, 7-P14
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