TP-5606 6/025-8 Controller Troubleshooting
Automatic Safety Shutdowns
Overspeed—The overspeed protection circuit board
monitors the output frequency of the generator set. If the
frequency is too high, the SDR relay on the circuit board
energizes. Normally open SDR contacts then close to
energize the K4 relay (LED4 lights). As a result, the
normally open K4A contacts close to latch the K4 relay
energized.
At the same time the K4A contacts close, normally
closed K4B contacts open to de-energize the FP (fuel
pump) motor and the K25 relay. The normally open K25
contacts then open to de-energize the FS (fuel supply)
solenoid, turning off the flow of fuel. With the fuel supply
and fuel pump both turned off, the engine turns off.
With the engine turned off, the generator output decays
and causes relays K1 and K5 to de-energize (LED1 and
LED5 go out). The normally open K1D contacts then
open, de-energizing the K2 relay (LED2 goes out) and
opening the normally open K2 contacts to interrupt
power to the remaining controller relay circuits,
including relay K4. As a result, the latch-up of the K4
relay is broken to return the controller circuits to a normal
prestart condition.
Engine Safety Switches— The engine is equipped with
two switches that monitor critical operating conditions.
These switches include:
D A High Engine Temperature Switch that closes
when the cooling water is not circulating properly
and the engine temperature rises toward an unsafe
level.
D A Low Oil Pressure Switch, which closes when the
oil pressure is insufficient, to indicate inadequate
lubrication of the engine.
During normal running, closing any one of the above
switches results in an engine shutdown. During start-up,
this shutdown function is disabled by normally open
contacts of the K5 relay until 5 to 10 seconds after the
engine starts in order to allow the monitored conditions
to stabilize.
Once the normally open contacts of K5 close, the engine
safety switches are enabled. If any of the switches close,
the K4 relay is energized to produce a shutdown in the
same manner as described above for an overspeed
condition.
K5
K4A
LED4
K4
K2
SDR
12 VDC
AH
AIR HEATER
AH
M
FS
S
10 A.
K25
K25
FP
10 A.
START
STOP/
PREHEAT
K1C
K1D
K1E
K2
K20
K3
K4
K2
K3
K20
S
B.C.
ALT
LED3
LED2
OP
WT
HR
K1A
VOLTAGE
REGULATOR
LED1 LED5
K1 K5
HR
BV
GEN
ON
REMOTE PANEL
K1F
K1B
SDR
OVERSPEED
PROTECTION
CIRCUIT BOARD
MAIN FIELD
8A.
LOW OIL
PRESSURE
HIGH
ENGINE
TEMP
Figure 5-8. Three-Phase Generator Sequence of
Operation, Emergency Shutdowns
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