5. ALTERNATOR REMOVAL AND DISASSEMBLY The alternator is the basic component of the charging system. The alternator is driven by the engine and provides alternating current which is converted to direct current by rectifiers and then used for battery charging. It also supplies current to the various systems in the vehicle such as lighting, ignition, etc. at the operating speed. The alternator is mounted on the engine block in such a way that the engine crankshaft belt provides drive to the alternator. Like the self starter it is also an electrical machine but functioning just the opposite; alternator converts mechanical energy into electrical energy. In this lesson we will study removal and dismantling of the alternator from the car.
5.0
Objectives After going through this lesson, you will be able to: Learn about electrical connections of the alternator. Remove the alternator from the car. Dismantle the alternator.
i. ii. iii.
5.1
Introduction
The alternator is provided to obtain electrical energy for charging the battery and also for other systems such as ignition, lighting etc. It is driven by the engine and thus converts the mechanical energy taken from the engine into electrical energy that is used to charge the battery. Rectifiers are used to convert the AC provided by the alternator into DC required by the battery. In order that the battery does not get overcharged, regulators are used. The alternator produces alternating current (AC) in its stator winding. Contrary to the self starter, in the alternator the field is rotated and the conductors remain stationary. In this lesson we will study how to remove the alternator from the car and dismantle it.
Self-check Questions 1. The alternator is driven by _________ and provides __________. 2. __________ are used to convert the AC provided by the alternator into DC. 3. Regulators reduce the amount of current that flows to the battery – True or False? 4. The alternator produces alternating emf in its _______ winding. 5. In the alternator, ___________ is rotated
5.2 • • • • • •
Removal Unlock the bonnet, lift it up and hook it. Unscrew the two bolts holding the bumper on both sides and remove the bumper. Unscrew the two screws from the upper member and remove the front grille. Loosen the clamp at the negative battery terminal and remove the earth cable. Pull out the coupler from the alternator. It has two terminals - ‘L’ and ‘IG’. Unscrew the nut and remove the connector at the ‘B’ terminal of the alternator.
The ‘B’ terminal is where the output of the alternator is collected and sent to the external circuit and also to the battery for charging. • • • • •
Loosen the bolt at the mounting stay so that the belt tension is released. Remove the V-belt from the belt pulley. Unscrew the 2 bolts holding the alternator to the bracket. Remove the bolt at the mounting stay. Remove the alternator from the car. After the alternator has been removed, it can be dismantled and inspected.
5.3 • • • •
Dismantling The following sequence of steps is followed to dismantle the alternator: Open the four bolts that hold the drive end frame and the rotor housing together. Unscrew the four bolts with a Philips-head screwdriver. It will be seen that these bolts are quite long. Hold the drive end frame in one hand and tap the rotor housing at the other end with a plastic hammer. Tap the drive end frame and lift it off.
Under the drive end frame is the rotor, which has the two field poles, the two slip rings, and the rear bearing. The front bearing is in the drive end frame. The rotor carries the field components in an alternator and hence the field is rotated while the conductors in the stator generate an electromagnetic force and supply current to the external circuit. The figure shows the stator and one brush. The other brush is behind this brush. Fig. 5.1: Stator and brush of alternator.
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Hold the rotor in the vise and loosen the drive end nut with a No 24 ring spanner. Remove the washer, the pulley discs, spacer, the fan ring, and the bush.
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Unscrew the three screws with a Philips-head screw driver. Loosen the rotor from the vise and placing the drive end housing over the jaws of the vice, tap the rotor with a plastic hammer and remove it from the drive end housing. The rotor is held in the drive end housing by the front bearing.
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Unscrew the nut at the ‘B’ terminal. Remove the nut, washer, and the insulating bush at the screw. Unscrew the other two nuts similarly. Unscrew the screw at the inside of the rotor housing and remove the stator along with the rectifier plate and the regulator assembly from the housing. Melt the solder joining the regulator assembly to the rectifier plate with a soldering iron and remove the regulator from the rectifier plate.
Fig. 5.2: IC regulator and brush holder.
As seen in the figure, the electronic integrated circuit regulator case also serves as the brush holder because the regulator and the brush holder are placed together as an integral unit.
Self-check Questions 6. How many terminals are there in the alternator socket? Which are they? 7. From which terminal is the output of the alternator collected?
5.4
Class Assignments
1. Discuss the purpose of providing an alternator in the car. 2. Discuss what could be the possible alternatives if there was no alternator in the car.
5.5
Summing Up
The battery gets discharged in the process of cranking the engine and in order to restore it to its fully charged state, an alternator is provided. Diode rectifiers and regulator are also provided along with the alternator to convert ac into dc and limit its output, respectively. Even though the alternator is an electric machine just like the self starter we studied in the previous unit, it differs in function and working from the starter motor. The
alternator produces alternating current (AC) in its stator winding and the field is rotated whereas in the starter motor the conductors were rotated and field was kept stationary. Revise the step-by-step procedure of removing and dismantling the alternator before proceeding to the next lesson.
5.6 1. 2. 3. 4. 5. 6. 7.
5.7
Possible Answers to Self-check Questions engine, alternating current rectifiers True stator field 2; L and IG B terminal
References
1. Maruti 800 Service Manual
5.8
Glossary
Alternating current Alternator Rectifiers Regulator Rotor Solder
Electric current that flows first in one direction and then in the other A device which produces ac (alternating current) which is converted to dc (direct current) to charge the car battery. Device consisting of diodes that changes alternating current to direct current A device that prevents production of excessive voltage in the alternator circuit Rotating armature Soft alloy used for joining metals