The electrical system is a negative ground system. The charging circuit operates when the engine is running. The alternator in the charging circuit produces direct current for the electrical system.
The components of the electrical system for the 3054E engine are described in this section.
- Electric starting motor
- Glow plugs
Electric starting motor (typical example)
The starting motor turns the engine flywheel. The rpm must be high enough in order to initiate a sustained operation of the fuel ignition in the cylinders.
The starting motor has a solenoid. When the ignition switch is activated, voltage from the electrical system will cause the solenoid to move the pinion toward the flywheel ring gear of the engine. The electrical contacts in the solenoid close the circuit between the battery and the starting motor just before the pinion engages the ring gear. This causes the starting motor to rotate. This type of activation is called a positive shift.
When the engine begins to run, the overrunning clutch of the pinion drive prevents damage to the armature which can be caused by excessive speed. The clutch prevents damage by stopping the mechanical connection. However, the pinion will stay meshed with the ring gear until the ignition switch is released. A spring in the overrunning clutch returns the clutch to the rest position.
The alternator is an electro-mechanical component that is driven from the crankshaft pulley by double belts. The alternator charges the storage battery during the engine operation.
The alternator converts the mechanical energy and the magnetic energy into alternating current and voltage. This conversion is done by rotating a direct current electromagnetic field on the inside of a three-phase stator. The electromagnetic field is generated by electrical current flowing through a rotor. The stator generates alternating current and voltage.
The alternating current is changed to direct current by a three-phase, full-wave rectifier. Direct current flows to the output terminal of the alternator. The rectifier has three exciter diodes. The direct current is used for the charging process.
A solid-state regulator is installed on the rear end of the alternator. Two brushes conduct current through two slip rings. The current then flows to the rotor field. A capacitor protects the rectifier from high voltages. The regulators are sealed and repair is not possible.
The alternator is cooled by an internal fan which is covered by the alternator housing. The fan pulls air through the holes in the front of the alternator. The air exits through the holes in the back of the alternator.
The diodes, the resistors, and the brushes are also covered by the alternator housing in order to protect the components from dirt and moisture.
The alternator is connected to the battery through the ignition switch. Therefore, alternator excitation occurs when the switch is in the ON position.
The electrically operated glow plugs are installed in the cylinder head near the fuel injection nozzles. The tips of the glow plugs reach into the combustion chamber in the piston crown. When the glow plugs are energized, the tips become very hot and the glow plugs improve the combustion during cold start conditions.