Most of SI engine
used battery ignition system. In this system a 6 volt or 12 volt battery used
to produce spark. Passenger cars, light truck, motorcycles and large stationary
engines are fitted with this system.
Main Parts of battery
ignition system:
Battery
A battery is used to provide energy
for ignition. It is work as storage of energy and charged by dynamo, which is
driven by engine. It converts chemical energy to electric energy.
Ignition switch
It is used to turn on and off the
ignition system. Battery is connected to the
primary winding of ignition coil by ignition switch and ballast resistor.
Ballast resistor
It is connected in series with
primary winding to regulate current in primary winding. It is used to prevent
injury due to overheating of ignition coil. It controls the current passes
through primary winding. It is made by iron. Iron has property of increase
electrical resistance rapidly by increase in temperature at certain limit. This
additional resistance resists flowing current which control the temperature of
ignition coil.
Ignition coil
Ignition coil is the main body of
battery ignition system. The purpose of ignition coil to step up the battery
voltage (6 or 12) to a high voltage, which is sufficient to produce spark at
spark plug. It consist a magnetic core or soft wire or sheet, and two
electrical winding called primary winding and secondary winding. The primary
winding has generally 200-300 turn and the end are connected to exterior
terminal. The secondary has almost 21000 turns of copper wire which is
insulated to withstand with high voltage. It is located inside the primary
winding and its one end connected to secondary winding and other end is
grounded either to primary winding or to the metal case. This entire unit is
enclosed in a metal container which makes it a compact unit.
Contact breaker
This is a mechanical device making
and braking the primary circuit to ignition coil. When the points are closed
current flow in ignition coil and when it open, flow of current stopped.
Capacitor
It is a simple electrical capacitor
in which two metal plate are separated by an insulating material with a
distance. Commonly air is used as insulating material but for particular
technical requirement some high quality insulating material is used.
Distributor
Distributor is used in multi cylinder
engine to regulate spark in each spark plug at correct sequence. It distribute
ignition surge in individual spark plug in correct sequence. There are two
types of distributor. One is known as carbon brush type and the other one is
gap type. In carbon brush type carbon brush carried by the rotor arm sliding
over the metallic segment embedded into the distributor cap or molded
insulating material. This makes electric connection or secondary winding with
spark plug. In gap type distributor electrode of rotor arm pass close to but
does not make contact with the distributor cap. So there is no wear of
electrode.
Spark Plug
A spark plug generally has two
electrodes which are separated with each other. A high potential discharge flow
through it which generate spark and ignite the combustion mixture in cylinder.
It mainly consist two electrodes a steel shell and an insulator. The central
electrode connected with the supply of ignition coil. It is well insulated with
the outer steel shell which is grounded. There is a small air gap between steel
shell and central electrode, between which spark is generated. The electrode
usually made by high nickel alloy so it can withstand with high temperature and
corrosion resistance.
Working of Battery Ignition System:
In the battery ignition system
ignition coil stores the energy in form of magnetic field and deliver it at the
instant of ignition, in form of high voltage current with high tension wire to
correct spark plug. The diagram of four cylinder battery ignition system is as
follow.
§ First
low voltage current flow form battery to the primary coil through ignition
switch and ballast resistor.
§
Ballast
resistor regulates the temperature of ignition coil by regulating current
passing form it.
§
The
ignition capacitor connected in parallel with contact breaker. One end of
secondary winding is also grounded through contact breaker.
§
When
the ignition switch is closed, the primary winding of the coil is connected to
the positive terminal, and current flow through it known as primary current.
§
The
current flows form primary coil produces a magnetic field which induces an EMF
in secondary coil.
§
The
cam regulate the contact breaker. Wherever the breaker open, current flows into
condenser, which charged the condenser.
§
As
the condenser become charger the primary current falls and the magnetic field
collapses. This will induces a much higher voltage in condenser.
§
Now
the condenser discharge into the battery which reverse the direction of both
primary current and magnetic field. This will induce a very high EMF in
secondary winding.
§
Now
this high voltage EMF produce spark at correct spark plug through distributor.
Advantages and
Disadvantages:
Advantages:
1. At the time of starting or at low
speed good spark is available.
2. The battery which is used to
generate spark can be used to light other auxiliary like headlight, tell light
etc.
3. Initial expenditure is less and it
has low maintenance
cost.
4. Ignition system is not affected by
adjusting spark timing in battery ignition system.
Disadvantages:
1. Time available of built up the
current and stored energy is decrease as speed of engine increases.
2. Contact breaker subjected to both
electrical and mechanical wear which results short maintenance interval.
3. The primary voltage decreases as
the engine speed increase. So it is not fully reliable of high speed engine.
Hi Avineet that's great.. Kp it up
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