Charging system
The mechanical energy of the engine
is converted into electrical energy by means of a Generator. This electrical energy is stored in the battery. The generator is driven by the engine crankshaft. To control the current flow, regulators are used. An ammeter is used to measure the current. The generator is also called a dynamo.
Construction and working of generator (or) Dynamo
Based on the Faraday’s laws of electromagnetic induction, the device which is used to convert mechanical
energy from engine in to electrical energy is called as Generator (or) Dynamo.
Important parts
1. Frame
2. Armature
3. Commutator
4. Brush
5. Pole shoe
6. Field coil
The engine crankshaft pulley drives the alternator through a V – belt drive at two to three times crankshaft
speed. Field coils are placed on each pole and are connected in series. Field coils produce an electromagnetic field and the armature conductors are rotated into the field. The armature cuts the magnetic fields and an emf is generated in the armature conductors. The commutator is to collect the current generated in armature conductors and DC is sent out through the carbon brushes.
Cut out relay
When the generator is operating, the
cutout relay closes the circuit, permitting the battery to get charged. When the generator stops, it opens the circuit, thereby preventing the battery from discharging back through the generator.bIt has two windings, namely shuntnand series. It has an armature carrying the
contact points. The armature is hingednand is kept away from the windings by a spring when the generator is not running. Once the generator starts, a tension is imposed on two windings of the cutout relay. It produces the magnetic field which
attracts the armature. As soon as the
tension produced by the generator is of sufficient value to force the charge into the battery, the magnetism is strong enough to pull the armature down overcoming the spring tension. This makes the contact point closes and thereby completing the circuit between the generator and the
battery. Thus, the battery gets charged.When generator stops, the armature loses the magnetism and the spring tension on the armature pulls the contact point away, thereby opening the circuit between the battery and the generator.
Alternator
The alternator converts mechanical
energy from the engine into electrical energy. It is also called A.C. Generator. With the help of rectifiers formed by diodes, the Alternating Current (AC) is converted into Direct Current (DC) and stored in vehicle battery. The rotor shaft usually consists of pole pieces with a field coil or winding
between them. When the current flows through the winding, it becomes an electromagnet. Current flows in and out of the winding through two brushes riding on slip rings. Each slip rings connects to one end of the winding. The current produces
a magnetic field which rotates as the rotor turned by engine crankshaft through a belt. The strength of the magnetic fields varies with the amount of the current flowing.
The stationary loops or conductors are assembled into a laminated iron frame. The assembly is stator. As the rotating magnetic field cuts through the windings,an alternating current is induced in the stator. As the magnetic poles are changing for every half revolution, stator induces an alternating current for every revolutionnof the rotor.
Advantages
• Light in weight
• A high output is obtained even at low engine speed.
• The cutout relay is not needed.
• Long life.
• Highly reliable.
