CONTROL PANEL SR4 GENERATOR MOUNTED Caterpillar


Standard Components

Usage:

AC Voltmeter

AC voltmeter (2) shows the potential difference (voltage) between phases T1/U and T2/V.

Oil Pressure Gauge

Oil pressure gauge (17) shows engine lubrication pressure in both kPa and psi.


Simplified schematic
(17) Oil pressure gauge.

As soon as the engine starts and switch ESS (CT) closes, oil pressure gauge (17) is connected across battery voltage. There is a relation between the current flow in this circuit and the engine oil pressure read on the gauge. The oil pressure sending unit controls the current flow by a change in resistance according to the change in engine oil pressure.

Water Temperature Gauge

Water temperature gauge (18) shows the engine coolant temperature in both centigrade (°C) and Fahrenheit (°F).


Simplified schematic
(18) Water temperture gauge.

As soon as the engine starts and switch ESS (CT) closes, water temperature gauge (18) is connected rcross battery voltage. There is a relation between the current flow in this circuit and the coolant temperature read on the gauge. The water temperature sending unit controls the current flow by a change in resistance according to the change in coolant temperature.

Engine Control Switch

The engine control switch can be turned to four positions:

STOP position - When turned to this position from the manual position, contact 11 (line 56) opens. When contact 11 is open the run relay (line 56) is deenergized and shuts down the engine. The ECS also opens contact 7 (line 36) and closes contact 8 (line 37). This will maintain battery (B+) to fault relays and fault lights that may have energized under a fault condition. The engine control switch should be kept in the STOP position while a fault is being corrected.

When the ECS is turned to the STOP position from the AUTO position, contact 10 (line 57) opens. When contact 10 is open, the run relay (line 56) is deenergized and shuts down the engine. The ECS also opens contact 6 (line 36) and closes contact 8 (line 37). This will maintain battery (B+) to fault relays and fault lights that may have energized under a fault condition. The engine control switch should be kept in the STOP position while a fault is being corrected.

OFF/RESET position - If a fault occurs, the engine will automatically shut down and light the correct fault light. The ECS is turned to the STOP position. After the fault is corrected, the ECS is turned to the OFF/RESET position to reset the fault relay and turn off the fault light. Power is still available to panel illumination lights (line 10) and the fault lamp test circuit. This position can also be used for normal shutdown of the engine.

AUTO position - For standby application, the ECS is turned to the AUTO position. In this position, the engine starts when remote initiating contact (line 58) closes.

MANUAL position - This position starts the engine. If a fault should occur, the panel will automatically shut the engine down and indicate the fault.

Four Light Fault Board

There are four fault indicator lights and relays mounted on a printed circuit board assembly. If the engine should overcrank or overspeed or have a coolant temperature above the upper limit or have oil pressure below the low limit, one of the four lights will light. At the same time, the engine will shutdown.


Four Light Fault Board And Schematic
(OCR) Overcrank relay. (OCL) Overcrank light. (OSR) Overspeed relay. (OSL) Overspeed light. (WTR) Water temperature relay. (WTL) Water temperature light. (OPR) Oil pressure relay. (OPL) Oil pressure light. (FFB) Four light fault board.

The light(s) remains lit with ECS in the STOP position. It also remains lit and cannot be reset if the emergency stop push button (ESPB) is pushed in.

To reset (turn off) the fault light(s), turn the ECS to the OFF/RESET position.

Each fault light indicator is a combination light and test button. A particular fault lamp can be tested by pushing in on the indicator light.

Fuses

The basic control panel has four fuses.


Partial Panel (fuse arrangement)
(1) Fuse A. (2) Fuse B. (3) Fuse 1. (4) Fuse 3.

Fuses A (1) and B (2) have a current rating of two amps. Fuse A is connected in series between generator output terminal T1 and voltmeter terminal 1. Fuse B is connected in series between generator output terminal T2 and voltmeter terminal 2. If either of these two fuses is defective, no voltage will be read on the meter.

Fuse 1 (3) has a current rating of 20 amps. This fuse is between battery (B+) and the engine fuel control solenoid. If this fuse is defective, the fuel solenoid will not function.

Fuse 3 (4) has a current rating of 10 amps. This fuse is between battery (B+) and the control panel. If this fuse is defective, the control panel will not function.

Hour Meter

The hour meter records the number of hours the generator has operated. Current flows to the meter when ESS(CT) contacts (11 and 10) are closed.

Magnetic Pickup


Typical Illustration
(1) Gap between gear and pickup. (2) Magnetic pickup.

The magnetic pickup is a single pole, permanent magnetic generator made of wire coils around a permanent magnet pole piece. As the teeth of the flywheel ring gear go through the magnetic lines of flux around the pickup, an AC voltage is generated. A positive voltage is generated when each tooth goes by the pole piece. Each time the space between the teeth goes by the pole piece, a negative voltage is generated. Engine speed is then determined by the frequency of these signals.

Engine Speed Switch

The engine speed switch (ESS) performs two main functions. The crank termination (CT) function drops the starter motor magnetic switch out of the circuit at a preset rpm.

The overspeed (OS) function will protect the engine should an overspeed situation occur.

Timers

The overcrank and arming delay circuits use identical timers. These timers will adjust from 0 to 100 seconds.


Timer
(1) Blue dot. (2) Red dot. (3) White dot. (4) Knob.

There is an arrow located on knob (4). When the arrow is pointing to blue dot (1), the timer will be set for 10 seconds. If the arrow is pointing to red dot (2) or white dot (3), the timer will be set for 30 and 90 seconds respectively.

Overcrank Timer

The OVERCRANK timer controls the amount of time the engine is allowed to crank while it is trying to start. The timer is factory set to 30 seconds.

When battery (B+) is applied to the timer (run relay contacts 6 and 9 [line 17] are closed), the timer begins. If the engine fails to start within the adjustable time period, the timer will energize the overcrank relay. When the overcrank relay is energized, the run relay coil is deenergized (RR contacts 6 and 9 open) and the engine stops cranking.

Arming Delay Timer

The ARMING DELAY timer controls the amount of time the oil pressure relay circuit is prevented from operating. The timer is factory set to 10 seconds.

When battery (B+) is applied to the timer (engine speed switch contacts 10-11, and run relay contacts 4-7 [line 20] are closed), the timer begins. Approximately ten seconds after the timer is energized, arming relay contacts 4-7 (line 39) close. This allows the engine time to develop enough oil pressure to open oil pressure contacts 1-3 and close contacts 1-2. If the engine does not have sufficient oil pressure to function properly, oil pressure contacts 1-3 will remain closed and energize the oil pressure relay and stop the engine.

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