Operational Test Procedures - Hobart 6921 Series Operation And Maintenance Manual

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
b. Operational Test Procedures
(1) Start the engine in accordance with instructions in 1-3; Para 2,A thru C.
(2) Check operation of engine instruments; DC ammeter (19, Fig. 1), Oil pressure gage (16) , and
hourmeter (18) .
(3) Check engine idle speed. It should read 650 to 700 RPM. Adjust, if necessary, in accordance
with instructions in Engine Operator's manual.
NOTE: A stroboscope is required for this check.
(4) Check for oil and fuel leaks, and correct any leaking conditions.
(5) Position switches and controls for automatic voltage regulation and power delivery as follows:
a. Place automatic-manual switch (31, Fig. 1) in AUTOMATIC position.
b. Place test-bank switch (32) in AIRCRAFT position.
c. Meter switch (6) may be in any position except pointing straight down.
d. If the adjustment of the voltage regulator rheostat (35) has been altered, position the knob to
mid-range position.
(6) Bring the engine up to governed speed, and energize the generator by holding the generator
mode control switch (17, Fig. 1) in BUILD-UP-VOLTS position momentarily. Release switch
and allow it to position in "center" RUN position. The governor and excitation-deenergization
relay circuits are functioning properly when engine "comes up" to governed speed [voltage value
appears on voltmeter (3, Fig. 1)].
(7) Observe the Frequency meter (1) . If engine speed is properly adjusted, frequency will be exactly
400 Hz. If not, adjust engine governed speed in accordance with Para. 4, E, (3) (d). See Fig. 12.
(8) Observe voltmeter (3) . Use rheostat (35) to adjust voltage to 115 V AC.
(9) Measure governor actuator input signal. See Para. 4, E, (4), (a).
(10) Measure governor magnetic pickup signal, See Para. 4, E, (4), (b).
(11) Check high-speed limiting governor. Engine limiting speed governor should limit engine speed to
just below trip point of overspeed governor. Overspeed device should trip at 2400 RPM.
February 28/94 Revised
Test Receptacle Connector
Terminals Identification
Figure 3
Chapter 2-3
Page 5