ARMY TM 9-6115-464-34
AIR FORCE TO 35C2-3-445-2
NAVY NAVFAC P-8-624-34
(2) Calculate the short-circuit current using the peak-to-peak amplitudes of the current trace and the
steady state ammeter reading prior to application of the short circuit. See figure 512.1-11.
(3) Tabulate the above results and the malfunction indicator indication for each line connection at each
voltage connection and compare the results with the requirement in table 4-1.
4-18. CIRCUIT INTERRUPTER TEST (OVERLOAD CURRENT)
a. General. A circuit interrupter is connected between the generator voltage reconnection system and the
generator output terminals to disconnect the generator output from the load and to protect the generator from a
sustained overload current. The circuit interrupter is operated from a current sensor external to the interrupter.
b. Apparatus. Instrumentation for measuring load conditions and field voltage and current shall be as
described and illustrated in MIL-HDBK-705. In addition, a stopwatch or an oscillograph with galvanometers
matching network and a non-inductive shunt as described and illustrated in MIL-HDBK-705, Method 106.1,
paragraph 106.1.3 and galvanometers having a flat frequency respond (within plus or minus 5%) from dc to
3000 Hz.
c. Procedure.
(1) Preparation for test. Connect the load and field instrumentation in accordance with the applicable
figure of MIL–HDBK–705, Method 205.1, paragraph 205.1.10 for one voltage and frequency.
CAUTION
(a)
(b)
(c)
(d)
If the circuit interrupter fails to operate within the time specified in table 4-1 at any time
during the performance of this method, manually open the circuit interrupter and
reduce the load impedance to rated value before reclosing the circuit interrupter.
Record on the data sheet the failure of the interrupter to operate and the total elapsed
time the overload was on the set. Failure to observe this caution could result in
damage to the equipment
Start and operate the generator set at rated voltage, rated frequency and rated load.
Allow the generator set to stabilize at rated load, voltage and frequency. During this period,
readings of the load and field instrumentation shall be recorded at minimum intervals of 10 minutes.
If necessary, adjustments to the load, voltage and frequency maybe made to maintain rated load at
rated voltage and frequency. Adjustment to the load, voltage or frequency shall be noted on the
data sheet. Stabilization will be considered to have occurred when four consecutive voltage and
current readings of the exciter field either remain unchanged or have only minor variations about an
equilibrium condition with no evident continued increase or decrease in value after the last load,
voltage or frequency adjustment has been made.
In one step, increase the load current to the overload current value specified in table 4-1 (the
increase in current may be accomplished by any practical means, e. g. reactively or using reduced
voltage levels).
NOTE
The frequency shall be maintained at rated conditions, the load current shall be kept
constant and the load current shall be balanced equally among the phases.
Simultaneously with the load current increase, start the stop watch.
Record all load instrumentation and the time, in seconds, required for the circuit interrupter to
operate.
4-18
