Guardian 4721, Руководство по ремонту

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DC CONTROL
LIQUID COOLED
ENGINE UNITS
SECTION 4.4
DIAGNOSTIC TESTS
PART 4
Page 91
TEST 21 - CHECK GENERATOR MAIN LINE
CIRCUIT BREAKER
DISCUSSION:
Transfer to the “Standby” power source cannot occur
unless that power supply is available to the transfer
switch. If automatic startup occurs while the genera-
tor’s main line circuit breaker is open, transfer to
“Standby” will not occur.
PROCEDURE:
1. Check that the generator’s main line circuit breaker is ON
or “Closed”.
2. Use an AC voltmeter (or a VOM) to check for proper gen-
erator AC output to the circuit breaker.
3. With the breaker set to ON or “Closed”, check for correct
AC output to the circuit breaker output terminals.
RESULTS:
1. If necessary, set the main circuit breaker to its ON or
“Closed” position.
2. If normal rated AC power is available to the breaker input
terminals, but not to the output terminals, replace the cir-
cuit breaker.
3. If normal rated AC power is not available to the breaker
AC input terminals, refer to Part 2 of this manual.
TEST 22 - CHECK SENSING TO CONTROL
BOARD
DISCUSSION:
In automatic mode and when a “Utility” power source
dropout occurs, the control board will initiate engine
cranking and startup. A line-to-neutral voltage/fre-
quency-sensing signal is delivered to the control
board from the generator’s AC power windings, via
Wires S15 and S16. This sensing signal “tells” the cir-
cuit board that the engine has started and is running.
Starter cutout occurs when the sensing signal voltage
reaches approximately 50 volts AC. The board’s mini-
mum run and engine warm-up timers will then turn on.
Transfer of loads to the “Standby” power supply can-
not occur until after the board’s engine warm-up timer
has timed out. Thus, if the Wires S15/S16 signal is
lost, transfer will not occur. This test will determine if
the line-to-neutral sensing signal is available to the
control board.
PROCEDURE:
1. Set the AUTO-OFF-MANUAL switch to OFF.
2. Turn OFF both the “Utility” and “Standby” power supplies
to the transfer switch.
3. If necessary, manually actuate the transfer switch main
contacts to their “Utility” position (“Load” terminals con-
nected to the “Utility” terminals).
4. Insert the test probes of an AC voltmeter across Pins A
and B of the control board, to which Wires S15 and S16
attach.
5. Turn ON the “Utility” power supply to the transfer switch.
6. Set the generator’s main line circuit breaker to its ON or
“Closed” position.
7. Set the generator’s AUTO-OFF-MANUAL switch to
AUTO.
8. While observing the AC voltmeter, turn OFF the “Utility”
power supply to the transfer switch.
a. The engine should crank and start in automatic
mode.
b. Starter cutout should occur at approximately 30
Hertz.
c. With engine running at rated speed, the volt-
meter should read about 122-126 volts AC.
RESULTS:
1. If correct voltage is indicated in Step 8, but transfer to
“Standby” did not occur, go on to Test 26.
2. If low or no voltage is indicated in Step 8, repeat Test 24.
a. If correct AC voltage is indicated in Test 24, but
not in Step 8 of this test, check sensing leads
S15 and S16 for an open or disconnected con-
dition.
b. If low or no voltage was indicated in Test 24,
refer to Part 2 of this manual.
TEST 23 - GROUND CONTROL BOARD
TERMINAL 23
DISCUSSION:
Following automatic startup and when the control
board’s engine warm-up timer has timed out (15 sec-
onds), circuit board action should connect Wire 23 cir-
cuit to ground. The transfer relay (in transfer switch)
should then energize and transfer to the “Standby”
source should occur. This test will determine if the
control board is working properly and is grounding the
Wire 23 circuit.
PROCEDURE:
1. Set the AUTO-OFF-MANUAL switch to OFF.