12-16. CIRCUIT INTERRUPTER (SHORT CIRCUIT)

Figure 12-5. Load Instrumentation (Sheet 2 of 2)

Figure 12-6. Apparatus Connection for Circuit Breaker (Short Circuit) Test

TM-9-6115-604-34 Generator Set Diesel Engine Driven Tactical Skid Mtd 5 Kw. 1 Phase-2 Wire 1 Phase -3 Wire 3 Phase -4 Wire 120. 120/240 and 120/208 Volts Manual
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TM 9-6115-604-34 NAVFAC P-8-633-34 c. Results (1) The overspeed protective device shall shut down the generator set each time an engine speed of 2070 to 2250 rpm is obtained, and the generator set shall not restart until the reset button is pressed, and both air boxes reset. (2) If the generator set does not shut down at the prescribed rpm, or can be started after a shut down without pressing the reset button, troubleshoot the overspeed protection circuit in accordance with Chapter 2. 12-16. CIRCUIT INTERRUPTER (SHORT CIRCUIT). a. General. A circuit interrupter is connected between the generator voltage reconnection system and the generator set output terminals to disconnect the generator output from the load and also to protect the generator from a short circuit. The circuit interrupter is operated from a current sensor external to the interrupter. b. Apparatus. Instrumentation for measuring load conditions shall be as illustrated in Figure 12-5. In addition, a noninductive shunt, a short-circuiting switch, a galvanometer matching network an oscillograph, and galvanometers having a flat frequency response (flat within plus or minus 5 percent) from DC to 3,000 Hz will be required. c. Procedure. (1) Preparation for Test. (a) Connect the load and instrumentation in accordance with Figure 12-5 and Figure 12-6, for one voltage and frequency. (b) Connect the shunt, galvanometer matching network, oscillograph, and short-circuiting switch across the load terminals of the phase being tested. (2) Test. (a) Start and operate the generator set at rated voltage, rated frequency, and rated load. (b) Set the oscillograph time marker to a minimum of 0.01 second or use a 60 Hz timing trace. Set the chart speed so that the individual peaks of the current waveform are clearly visible, and adjust the peak-to-peak rated current amplitude to a minimum of 0.5 inch (13 mm). (c) Before dosing the short-circuiting switch, record a portion of the steady-state load for calibration. With the same load conditions record all instrument readings. CAUTION If the circuit Interrupter fails to operate within the specified time, open the short circuit switch to prevent damage. Note the failure to operate on the data sheet. (d) With the oscillograph still recording the steady-state current, dose the short-circuiting switch. (e) The generator set contains an overload malfunction indicator; check and record its indication. (f) Restart the generator set, and test the time delay by momentarily dosing and opening the short circuit switch. When performing this test, the short circuit switch shall not be dosed longer than 9 seconds. (g) Repeat steps (a) through (e), above, for each possible short circuit (L₁-L₀, L₂-L₃, L₁-L₂-, L₃, etc.) (h) Repeat steps (a) through (g), above, for all voltage connections. d. Results. (1) From the oscillograms taken in step (2)(d), above, determine the time between the indicated closure of the short-circuiting switch and the opening of the circuit interrupter. See Figure 12-7. (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. (3) Use the oscillograms taken in step (e), above, and determine if the circuit interrupter actuated upon application of the momentary short circuit. (4) Tabulate the above results for each line connection, and compare the results with the requirements in Table 12-3. 12-22

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