The charging circuit operates when the engine is running. The alternator in the charging circuit produces direct current for the electrical system.
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| Illustration 1 | g01964824 |
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Typical example 12 V 4 kW Starting Motor (1) Terminal 30 for connection of the battery cable (2) Terminal 50 for connection of ignition switch (3) Terminal 31 for connection of the ground | |
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| Illustration 2 | g01964833 |
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Typical example 24 V 5.5 kW Starting Motor (4) Terminal 30 for connection of the battery cable (5) Integrated Magnetic Switch (IMS) (6) Terminal 50 for connection of ignition switch (7) Terminal 31 for connection of the ground | |
The starting motor turns the engine via a gear on the engine flywheel. The starting motor speed must be high enough in order to initiate a sustained operation of the fuel ignition in the cylinders.
The starting motor consists of the main armature and a solenoid. The solenoid is a relay with two windings Pull-In (PI) and Hold-In (HI). Upon activation of ignition switch, both windings move the iron core by electromagnets. The linkage from the iron core acts to move the pinion toward the flywheel ring gear for engagement. Upon complete engagement, the solenoid completes the high current circuit that supplies electric power to the main armature in order to provide rotation. During cranking of the engine, only the Hold-In (HI) winding is active.
The ignition switch is deactivated once the desired engine speed has been achieved. The circuit is disconnected. The armature will stop rotating. Return springs that are located on the shafts and the solenoid will disengage the pinion from flywheel ring gear back to the rest position.
The starting motor has an overrunning clutch to prevent damage to the starting motor and mechanical transmissions as the engine speed increases.
Certain higher powered starting motors are designed with an Integrated Magnetic Switch (IMS). The Integrated Magnetic Switch (IMS) is activated by the ignition switch. The solenoid circuit then engages the starting motor. The benefit of Integrated Magnetic Switch (IMS) is a lower current in the ignition circuit that will allow the engine ECM to control ignition without the use of a relay.
The electrical outputs of the alternator have the following characteristics:
- Three-phase
- Full-wave
- Rectified
The alternator is an electro-mechanical component. The alternator is driven by a belt from the crankshaft pulley. The alternator charges the storage battery during the engine operation.
The alternator is cooled by an external fan which is mounted behind the pulley. The fan may be mounted internally. The fan forces air through the holes in the front of the alternator. The air exits through the holes in the back of the alternator.
The alternator converts the mechanical energy and the magnetic field 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 direct current is used for the charging process.
A 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 alternator is connected to the battery through the ignition switch. Therefore, alternator excitation occurs when the switch is in the ON position.