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 MIL-HDBK-1023/4
5.6.1
Preventive Maintenance Inspection Procedures. The procedures for the PMIs are
listed in Table 12. Where measurement of current is called for, use a clamp-on ammeter,
instrument transformer and ammeter, or similar setup. Do not use the ammeter on the face of the
regulator. This meter does not have the accuracy required for these measurements.
a) Daily Checks. Check all control equipment for proper operation. Check remote
control and/or radio control on each brightness step.
b. Monthly checks
(1) Check and record regulator input voltage and input current. If the voltage is not
correct (must be within 5 percent of design voltage), notify the power company to correct the
input voltage.
(2) Ensure that the load value does not exceed the given kW rating of the regulator.
(3) Check and record the output current into the circuit loop on each brightness
step. Compare results with the tolerances listed in the following paragraphs defining required
annual checks. Consult the manufacturer's instruction book for information on adjusting output
current.
c) Annual checks
(1) Visually check regulator for burned relay contacts, frayed or burned insulation,
and loose connections. If contacts are burned or pitted completely through the silver contact
surface, they should be replaced. If the contacts do not touch at all points, or if they are slightly
pitted or dirty, they should be cleaned. A fine file is the most desirable tool for surface cleaning.
After cleaning, the contacts should be realigned before the regulator is put into operation.
(2) Make a dielectric strength test of the oil. Take at least a 1-pint sample of oil
through the oil sampling valve at the base of the regulator tank. The test may be conducted with
the oil-tester described in par. 4.10. If no facilities are available for making dielectric tests,
contact the nearest power company equipped to perform these tests. If the oil is dirty or the
dielectric strength is low, it should be replaced or filtered and dried to restore its dielectric
strength. Sludge deposits on the core and coil assembly and in the tank should be washed out
with clean dry oil. Models with an internal primary switch will tend to collect more sludge due
to arcing under oil. Fill with oil to the proper level.
WARNING - ELECTRICAL HAZARD:
Since high open-circuit voltages may be obtained by opening the primary side of
a series lighting circuit, only authorized personnel should be allowed to perform
the short-circuit test, open-circuit test, and the load test.
A series circuit connected across a 50 kW, 20.0-ampere regulator may have a full load voltage of
2,500 volts. However, the momentary surge before the open-circuit protection device actuates
will approach 5,000 volts.
(3) Short-Circuit Test. Make a short-circuit test as follows:
(a) Turn off power to regulator.
(b) Short the output terminals using No. 10 AWG wire (or larger) across the
terminals.
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