Hobart 140GT17P Operation And Maintenance Manual With Illustrated Parts List page 80

OM-2029
(33) Operate at 125% rated load for 5 minutes immediately following the fullload run. The overload de-
vice MUST trip within 5 minutes and the overload indicating light (12, Fig. 1) must come ON to indi-
cate an overload condition.
(34) Reduce load to normal. Turn off indicating light by pressing reset switch (3, Fig. 1).
(35) Check engine oil pressure at governed speed (1714 RPM). Gage should indicate at least 38 PSI
when the engine is hot. Check engine coolant temperature. Gage should indicate in the range of 180
degrees to 190 degrees depending upon ambient temperature.
(36) Check operation of protective system interlock relay for each output.
(a) Check No. 1 output protective interlock relay
Close No. 1 load contactor switch (18) and apply 1/2 load to the generator set. With unit operating
at 1/2 load, press the upper (test) poetion of the TEST-RESET rocker switch (3). The No. 1 load
contactor should open immediately, with all fault lights coming ON. This indicates that the No. 1
protective system interlock relay is functioning properly. Press the lower (reset) portion of the
TEST-RESET switch. Fault light will go off.
(b) Check No. 2 output protective interlock relay
Close No. 2 load contactor switch (20) and apply 1/2 load to the generator set. With unit operating
at 1/2 load, press the upper (test) portion of the TEST-RESET rocker switch (3). The No. 2 load
contactor should open immediately, with all fault lights coming ON. This indicates that the No. 2
protective system interlock relay is functioning properly. Press lower (reset) portion of the TEST-
RESET switch. Fault lights will go off.
(37) Check operation of overvoltage relay and indicating light.
(a) With No. 1 load contactor closed and the unit running at 1/2 load, adjust the voltage regulator
to increase voltage until the overvoltage sensing relay actuates the protective monitor to open the
load contactor and turn on the overvoltage indicating light. The overvoltage sensing relay should
trip when voltage reaches 130V to 134V.
(b) Return unit to normal operating conditions by adjusting voltage regulator rheostat and press-
ing reset switch (3).
(38) Check operation of undervoltage sensing relay, indicating light and time delay. Before starting
this check, let us understand the sequence of events which should happen when the voltage is re-
duced to 103V or lower. At some value between 103V and 93V, the undervoltage sensing relay
should function to activate the undervoltage time delay circuit. Five seconds after the time delay cir-
cuit is activated, (if the undervoltage condition continues) it should function to open the protective
monitor relay which, in turn, will open the load contactor to stop power delivery. As a result of the ac-
tion, the undervoltage indicating light (11) should be turned ON. A stopwatch or sweep-second-hand
watch is required for this check. Proceed as follows:
(a) With the No. 1 load contactor closed and the unit running at 1/2 load, use the voltage regulator
rheostat to reduce voltage to 104V. Remember to turn the voltage regulator rheostat CLOCK-
WISE for this. The load contactor should NOT open after a 5-second delay.
(b) Reduce voltage in steps of 1V, with a delay of at least 5-seconds between steps. Restart stop-
watch or note position of swee-second-hand each time voltage is reduced. At some voltage value
between 103V and 93V, and 4 to 12 seconds after a new voltage setting is made, the load contac-
tor should be opened and the undervoltage indicating light should be turned on by the step-by-
step action of the undervoltage sensing relay, time delay circuit, and protective monitor relay.
(c) If the load contactor is not opened at 103 V to 93 V, it will be necessary to refer to the Trouble
Shooting Chart, Section 3-1, to determine which component of the undervoltage protective circuit
is defective.
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September 30/89 Revised