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Charging System Components
Alternator
Alternator Components (Typical Example)
(1) Brush holder. (2) Rear frame. (3) Rotor. (4) Stator. (5) Drive end frame. (6) Fan assembly. (7) Slip rings. (8) Rectifier.The alternator used on the 3116 Truck Engines has three phase, full-wave, rectified output. It is a brush type alternator.The alternator is an electrical and mechanical component driven by a belt from engine rotation. It is used to charge the storage battery during engine operation. The alternator is cooled by a fan that is a part of the alternator. The fan pulls air through holes in the back of the alternator. The air exists the front of the alternator, cooling it in the process.The alternator converts mechanical and magnetic energy to alternating current (AC) and voltage. This process is done by rotating a direct current (DC) electromagnetic field (rotor) inside a three phase stator. The alternating current and voltage (generated by the stator) are changed to direct current by a three phase, full wave rectifier system using six silicone rectifier diodes. The alternator also has a diode trio which is an assembly made up of three exciter diodes. The diode trio rectifies field current needed to start the charging process. Direct current flows to the alternator output terminal.A solid state regulator is installed in the back of the alternator. Two brushes conduct current, through two slip rings, to the field coil on the rotor.There is also a capicitor mounted in the back of the alternator. The capacitor protects the rectifier from high voltages. It also suppresses radio noise.Regulator
The voltage regulator is a solid state (transistor, stationary parts) electronic switch which controls the alternator output. The regulator limits the alternator voltage to a preset value by controlling the field current. It feels the voltage in the system and switches "ON" and "OFF" many times a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output. Refer to Service Manual, Form No. SENR3862, for detailed service information for the Delco Remy 21 SI Series Alternator. For engines which have the alternator connected to an engine component, the ground strap must connect that component to the frame or to the battery ground.Starting System Components
Starter Solenoid
A solenoid is a magnetic switch that does two basic operations:1. Closes the high current starter motor circuit with a low current start switch circuit.2. Engages the starter motor pinion with the ring gear.
Typical SolenoidThe solenoid switch is made of an electromagnet (one or two sets of windings) around a hollow cylinder. There is a plunger (core) with a spring load inside the cylinder that can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is made that pulls the plunger forward in the cylinder. This moves the shift lever (connected to the rear of the plunger) to engage the pinion drive gear with the ring gear. The front end of the plunger then makes contact across the battery