GENERATOR SET CONTROL PANEL Caterpillar

Location Of Components

Control Panel - Front View

(1) AC Ammeter (AM).

(2) AC Voltmeter (VM).

(3) Frequency meter (FM).

(4) Spare fault light.

(5) Engine overspeed fault light.

(6) High coolant temperature fault light.

(7) Low oil pressure fault light.

(8) Voltage adjust rheostat (VAR).

(9) Ammeter/Voltmeter phase selector switch (AVS).

(10) Start aid switch (SAS) - optional.

(11) Governor switch (GS) - optional.

(12) Water temperature gauge (WTG).

(13) Oil pressure gauge (OPG).

(14) Key switch (KS).

(15) Four light fault board (FFB).

(16) Frequency meter resistor (FMR).

(17) Terminal board (TBC).

(18) Fuse block (FB).

(19) Name plate.

(20) Slave relay 1 (SR1).

(21) Circuit breaker 2 (CB2).

(22) Starting motor magnetic switch 1 (SMMS1).

(23) Fuse 1 (F1) - fuel shutoff solenoid.

(24) Fuse 2 (F2) - control panel.

(25) Electronic speed switch (ESS).

(26) Engine failure relay (ENFR).

(27) Arming relay (AR).

(28) Arming delay timer (ADT).

The control panel is mounted on the generator terminal box. Each control panel has a specific nine character model number. An example of a typical model number is "T3C3HXRX0". The model number is stamped on name plate (19) which is located inside the control panel on the bottom. The model number is based on control panel options and generator ratings. Each character of the model number specifies a particular component of the control panel. Included with every control panel is 130-3786 Control Panel Chart. The chart print explains the meaning of each character of the model number.

Control Panel Interior

Component Description

AC Schematic (JIC)
AM - AC Ammeter. AVS - Ammeter/Voltmeter Phase Selector Switch. FA,FB,FC - Fuses. FM - Frequency Meter. L1,L2,L3 - Load Leads. T1,T2,T3 - Generator Line Leads. VAR - Voltage Adjust Rheostat. VM - AC Voltmeter.

Ammeter/Voltmeter Phase Selector Switch (AVS)

Show/hide table

To avoid personal injury due to electrical shock, make sure jumpers are installed correctly on the AVS.

For reference, see the preceding AC Schematic illustration.

The ammeter/voltmeter phase selector switch (AVS) allows the operator to select which electrical phase is shown on the AC ammeter (AM) and the AC voltmeter (VM). The AVS has four positions:

* When in position 1, the AM shows T1 phase current and the VM shows T1-T2 phase voltage. AVS contacts 1, 2, 5, 6, 9, 10, 14, 15 and 17 of the AVS are closed.

* When in position 2, the AM shows T2 phase current and the VM shows T2-T3 phase voltage. AVS contacts 1, 3, 5, 7, 9, 11, 14, 15 and 16 are closed.

* When in position 3, the AM shows T3 phase current and the VM shows T3-T1 phase voltage. AVS contacts 1, 4, 5, 8, 9, 12, 15, 16 and 17 are closed.

* When in position OFF, nothing is shown on the AM and the VM. AVS contacts 13, 14, 16 and 17 are closed.

AC Ammeter (AM)

For reference, see the preceding AC Schematic illustration.

The AC ammeter (AM) shows the amperes of the line current in phase 1, phase 2 or phase 3. The ammeter/voltmeter phase selector switch (AVS) is used to select the phase which is shown on the AC ammeter. The AVS connects the AM to a current transformer (CT1, CT2 or CT3) on phases T1, T2 or T3 respectively. The CT's transform the actual line current of the respective phase lead to a level (approximately 0 to 5 amps) which is within the input range of the AM. The AM is calibrated (has marks) to give an indication of the actual current flow in one phase of the generator.

AC Voltmeter (VM)

For reference, see the preceding AC Schematic illustration.

The AC voltmeter (VM) shows the voltage between phases T1-T2, phases T2-T3, or phases T3-T1. The ammeter/voltmeter phase selector switch (AVS) is used to select the phase which is shown on the VM. T1-T2 phase voltage is shown on VM when AVS is in position 1. T2-T3 phase voltage is shown on VM when AVS is in position 2. T3-T1 phase voltage is shown on VM when AVS is in position 3.

Frequency Meter (FM)

For reference, see the preceding AC Schematic illustration.

The frequency meter (FM) shows the frequency in hertz (Hz, cycles per second) of the alternating current being made by the generator set. There is a direct relation between the frequency of the electricity and the RPM of the engine, as shown in the following formula:

NOTE: A frequency meter resistor (FMR) is required for generators with operating voltages exceeding 240 VAC.

Voltage Adjust Rheostat (VAR)

For reference, see the preceding AC Schematic illustration.

The voltage adjust rheostat (VAR) connects to the voltage regulator and is used to adjust the voltage output of the generator. The VAR replaces the voltage level rheostat located on the generator voltage regulator assembly.

NOTE: When the VAR is used with the VR3 voltage regulator, there is NO jumper wire connecting terminal four and terminal seven of the VR3.

Start Aid Switch (SAS) - Optional

The optional start aid switch (SAS) is used to inject ether into the engine for starting in cold weather conditions. The SAS is a spring return switch which has to be held in the ON position to activate. When the key switch is in the START position and the SAS is pressed and held in the ON position, the start aid solenoid valve (SASV) energizes and meters a specific amount of ether into a holding chamber. When the SAS is released, the SASV de-energizes and the ether is released to the engine.

If the temperature of the engine is high enough to open the start aid temperature switch (SATS), then the SAS cannot activate ether injection.

Governor Switch (GS) - Optional

The optional governor switch (GS) is available when the engine governor is equipped with a speed adjust (synchronizing) motor. The GS is used to raise or lower the engine speed. The GS makes the synchronizing of generators easier. After the engine is running, the governor switch (GS) is enabled, permitting a change in engine rpm (generator frequency). Pressing and holding the GS in the up position will increase engine rpm. Pressing and holding the GS in the down position will decrease engine rpm.

Key Switch (KS)

For reference, see the DC Schematics.

The key switch (KS) is used to start and stop the engine. The key switch (KS) has three positions: STOP, START and RUN.

STOP position - When turned to this position from the RUN position, contact R opens. This de-energizes the slave relay (SR1) and the engine shuts down. If a fault has occurred and the KS is turned to the STOP position, all fault relays and fault lights will shut off and are reset. The key switch must remain in the RUN position for the fault light to stay ON. The key switch should be kept in the STOP position while a fault is being corrected.

START position - This position energizes the starting motor magnetic switch (SMMS) and the engine cranks. The START position is spring loaded to return to the RUN position. There is a mechanical block within the KS that prevents returning the KS to the START position without going to the STOP position first. This prevents cranking the engine while the engine is running. To restart the engine, turn the key switch to the STOP position before again turning to START.

RUN position - During normal operation, the RUN position allows the engine to operate until the key switch is turned to the STOP position. If a fault should occur, the control panel will automatically shut the engine down and the corresponding fault light will illuminate. The key switch must remain in the RUN position for the fault light to stay ON. The key switch should be turned to the STOP position while a fault is being corrected.

Oil Pressure Gauge (OPG)

DC Schematic Of Oil Pressure Gauge

The oil pressure gauge (OPG) shows engine oil pressure. The OPG is powered whenever the key switch is in the RUN position. The value shown on the OPG is proportional to the flow of current through the OPG. The current flow is controlled by the resistance of the oil pressure sending unit (OPSU). As the oil pressure changes there is a corresponding change in the resistance of the OPSU and therefore a corresponding change in the value shown on the OPG.

Water Temperature Gauge (WTG)

DC Schematic Of Water Temperature Gauge

The water temperature gauge (WTG) shows the engine water temperature. The WTG is powered whenever the key switch is in the RUN position. The value shown on the WTG is proportional to the flow of current through the WTG. The current flow is controlled by the resistance of the water temperature sending unit (WTSU). As the water temperature changes there is a corresponding change in the resistance of the WTSU and therefore a corresponding change in the value shown on the WTG.

Four Light Fault Board (FFB)

Four Light Fault Board (FFB)
(OPL) Oil Pressure Light
(OPR) Oil Pressure Relay
(OSL) Overspeed Light
(OSR) Overspeed Relay
(SPL) Spare Fault Light
(SPR) Spare Fault Relay
(WTL) Water Temperature Light
(WTR) Water Temperature Relay

There are four fault indicator lights and relays mounted on a printed circuit board assembly. The board assembly mounts to the inside face of the control panel. The purpose of the four light fault board is to activate an engine shutdown and to inform the operator or service personnel as to the cause of the shutdown.

When any one of the following conditions exist, the corresponding fault light will illuminate, the corresponding relay will energize and the engine will shutdown.

* If the engine should overspeed as determined by the electronic speed switch (ESS).

* If the engine water temperature should rise above the upper limit of the water temperature switch (WTS).

* If the engine oil pressure should fall below the low limit of the engine oil pressure switch (OPS).

* If a shutdown condition should occur for the spare fault as determined by the customer.

As long as the key switch is in the RUN position, the corresponding relay will remain energized and the corresponding fault light indicator will remain lit. To de-energize the relay and to turn off the fault light indicator, turn the key switch to the OFF position.

Each fault light indicator is a combination light and test button. The lamp of a particular fault light indicator can be tested by pushing the indicator in. The lamp will remain lit as long as the indicator is pushed in. If the lamp does not illuminate, replace the bulb.

The relays are the miniature type and are 4PDT. The relay coils are 24 DCV with a maximum pickup voltage of 14 DCV. The relay contacts are 5 amp maximum at 24 DCV resistive. The individual relays and fault light indicators are not replaceable.

Fuses

The basic control panel has five fuses located inside on the bottom of the control panel.

Fuse A (two amps) is connected in series between the generator output terminal T1 and terminal 2 of the ammeter/voltmeter phase selector switch (AVS). If this fuse is faulty, no frequency reading will be shown on the frequency meter.

Fuse B (two amps) is connected in series between the generator output terminal T2 and terminal 7 of the ammeter/voltmeter phase selector switch (AVS). If this fuse is faulty, no frequency reading will be shown on the frequency meter.

Fuse C (two amps) is connected in series between the generator output terminal T3 and terminal 3 of the ammeter/voltmeter phase selector switch (AVS). If this fuse is faulty, no voltmeter reading will be shown when the AVS is position 3 (T3-T1 phase voltage).

Fuse 1 (20 amps) is connected between battery (B+) and the engine fuel control solenoid. If this fuse is faulty, the fuel solenoid will not function.

Fuse 2 (10 amps) is connected between battery (B+) and the control panel. If this fuse is faulty, the control panel will not function.

Arming Delay Timer (ADT)

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

The purpose of the arming delay timer (ADT) is to prevent the activation of an oil pressure fault during the time immediately following engine starting. Low oil pressure is normal for a short period of time after engine starting. The ADT controls the amount of time that the oil pressure relay circuit is disabled after engine cranking. The timer is factory set to 15 seconds.

The arming delay timer is adjustable from 0 to 100 seconds. Three dots on the board correspond to a value of time. There is an arrow located on knob (4). When the arrow is pointing to a particular dot, the corresponding value of time is selected.

Blue dot (1) ... 10 seconds

Red dot (2) ... 30 seconds

White dot (3) ... 90 seconds

DC Schematic Of Arming Delay Timer (ADT)

When battery (B+) is applied to the ADT (key switch contacts B-R [lines 11 and 13] are closed), the ADT (line 15) begins. Approximately ten seconds after the ADT is energized, arming relay (AR) contacts (line 43) close. This allows the engine time to develop enough oil pressure to open oil pressure switch (OPS) contacts 1-3 and close contacts 1-2. If the engine does not have sufficient oil pressure to function properly, OPS contacts 1-3 will remain close. This will energize the oil pressure relay (OPR) and shutdown the engine for an oil pressure fault.

Electronic Speed Switch (ESS)

Electronic Speed Switch (ESS)

The electronic speed switch (ESS) performs the function of protecting the engine from overspeeding. A magnetic speed pickup (MPU) supplies the ESS with engine speed information. The ESS evaluates the speed information. If the engine speed is greater than the limit, the ESS activates the overspeed relay (OSR). Then the OSR activates the engine failure relay (ENFR) which deactivates the slave relay (SR1). With SR1 deactivated, contacts 30 and 87 of SR1 open and the fuel solenoid (FS) is de-energized. Fuel is no longer provided to the engine and the engine stops.

Reference: For Overspeed Calibration and Overspeed Verify tests of the ESS, see the service procedures section of SENR3207, Troubleshooting Guide (ETR).

Magnetic Speed Pickup (MPU)

Magnetic Speed Pickup (MPU)

The purpose of the magnetic speed pickup (MPU) is to send a signal which represents the speed of the engine to the ESS. The MPU is located on the engine flywheel housing. The MPU 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. The ESS counts the frequency of the this speed signal and determines the speed of the engine.