Project - Analysis of a practical automotive wiring circuit

Answer 1 - The Major elements in the automotive wiring diagram are as follows :

• Generator
• Starter
• Breaker
• Ignition Coil
• Current and Voltage Regulator
• Distributor
• Foot Selection Switch
• Ammeter

Answer 2 -

Generator: Mechanical energy is transformed into electrical energy via a generator. When the engine is running, a steady battery charge is provided. Almost all of the systems in a contemporary car are managed by sensors that keep track of their various operating modes. Since the battery is entirely depleted, the automobile would not even have time to warm up if all these components relied on the battery charge to function. A generator is placed so that each system won't need to be powered by a battery when the motor is running. It is required to replenish the battery and only functions when the internal combustion engine is running. Additionally, it supplies enough power for each component of the machine's electrical system.

Working of a Generator: The mains are turned on when the key is turned in the ignition lock. The regulator sends the voltage from the battery to the copper slip rings, and the rotor excitation winding is the final consumer.

An electromagnetic field is produced as soon as the engine crankshaft starts to turn and the rotor shaft begins to turn through the belt drive. When a particular speed is reached, the rotor generates an alternating current, and the excitation winding is then powered directly by the generator rather than the battery. The "equalization" process occurs as the alternating current travels to the diode bridge. The voltage regulator keeps track of the rotor's working mode and adjusts the voltage of the field winding as appropriate. So long as all of the components are in working order, a steady current is sent to the battery, giving the onboard network the necessary voltage.

Starter: A starting motor is a compact but effective electric motor used to start an internal combustion engine by converting electrical energy into mechanical (rotational) energy. It takes a lot of effort to start an automobile. To start the car, the starter motor is made to operate precisely.

Working of a Starter: The heart of the starting mechanism is a starter motor and solenoid, which work together closely. Without the starting motor, a vehicle cannot move. It is required to start the engine. The engine needs to be turned on at a certain speed to finish the combustion cycle and start the engine. Electric current needs to be at an extremely high level for the starter motor. It uses 12 volts of DC power, which is delivered from the battery by a hefty cable. When starting the engine, a strong starter motor is needed to accelerate it to a speed at which it can operate smoothly at low RPM. Once the engine has started and is operating on its own power, the starter motor is no longer required, adding to its burden until the next start. The "S" terminal of the solenoid, which is often a pin-type or a small stud-type terminal installed on the back of the solenoid cap, receives current when the ignition key is turned or the start button is pressed. There will be an electromagnetic field produced when these windings are powered up. The rod within the solenoid known as a plunger is drawn in by this electromagnetism. This performs two tasks at once. One is that the lever fork, which is coupled to the end of the plunger, moves the pinion gear in the direction of the flywheel.

Breaker: A circuit breaker's operation is more or less comparable to that of a fuse. The fuse needs to be replaced every cycle when a significant amount of current is trying to pass through it, which is the fundamental difference between the two. Its core structure is harmed by this powerful current. The fact that the circuit breaker nearly never has to be replaced is hence its main advantage.

Working of a Breaker: A circuit breaker has an electromagnet that the current passing through it can energize or de-energize. The electromagnet component cannot energize if the current passing is within a safe working level. Instead, the metallic blade, whose one end is connected to the electromagnet and the other to the stationary contact that is further connected to the next section of the circuit, maintains its contact and the current simply passes through the circuit breaker to the external circuitry.
The electromagnet part will ultimately become ignited when the current exceeds the safe working level and increases significantly due to a system fault. This additional power will be sufficient to separate the main contact, which is connected to the external circuit, from the contact of the metallic part. The current path immediately encounters an endless amount of resistance when the circuit opens from this point and is unable to continue. The circuit operates securely when the current returns to its previous level because the electromagnet part is de-energized and the contact is maintained once again.

Answer 3 - Given: Load = 10A

Normal load current = 1 Amp

Normal fuse size = 1.5 Amps (135% of full load current)

So, For a 10A full load current the fuse rating should be

= 10 * 135% = 13.5 A

In order to comply with the standard fuse rating, we consider the next higher standard size i.e 15A.

Thus, for a 10A full load, the current fuse rating should be 15A.

Answer 4 - Given: Load = 500W

Considering the voltage of the battery is 12V DC,

P = VI

Therefore 500 = 12 * I

I = 500/12

I = 41.66 A

Now, Efficiency is 85%

Therefore, I = 41.66 * 0.85

I = 35.41 A

Considering it runs for 3 hours,

Battery capacity = Ah * V

= 500 * 3 * 12

= 18000 Wh = 18 kW-h

If the battery runs in 24V DC,

Battery capacity = 500 * 3 * 24 = 36000 Wh

Therefore the battery capacity = 36 kWh

Answer 5 - The Generator and the junction box are in parallel connection. Generators are used in parallel to increase the total system size and redundancy. Advantages of paralleling it with Junction boxes include the increase in efficiency, expandability, ease of maintenance, and redundancy. Junction box basically contains the sensors hence connecting it to parallel helps with the output.

Answer 6 - The Ammeter and Fuel Gauge are in series connection. Ammeter is always connected in series with the load so that there is the same current in both. This can only be possible if the resistance on the ammeter is very low so as to ensure correct measurement of current in the circuit. The two units are connected in series to a contact voltage regulator, which is energized when the ignition switch is turned on. The Fuel gauge is connected in series because it is required to directly monitor the fuel level at all times.