Project - Analysis of a practical automotive wiring circuit

1.

• Ammeter
• Generator
• Switch
• Fuse
• Earth
• Battery
• Starter Motor
• Circuit Breaker
• Current & Voltage Regulator

2. Fuse:A fuse is a safety device used to protect the circuit when a current more than the rated current is passing through the circuit. It protects the devices connected in that circuit from damage. For it to work, it is connected in series with the power source. When the current flowing through the wire is higher than the desired value, the fuse blows (Ruptures) and the circuit is open and no current passes through it until the fuse is replaced. There are several types of fuses like rewirable type, High rupture capacity type, catridge type etc..

Earth : Earthing or Grounding is done to prevent damage to the devices in the circuit as well as protect the operator from shock. It is done by connecting a specific part of the circuit to the ground (In automotives, the chassis is the ground). The negative terminal of the power source is connected to the chassis and so is the negative side of the devices in the circuit. They all are connected to the common ground (Vehicle chassis). The circuit loop is complete and current starts to flow through. The type of earthing here is chassis ground.

Ammeter: It is a device used to measure the value of current in the circuit. It is connected in series with the circuit. It is constructed to offer least resistance internally and hence the better accuracy of measurement. Each ammeter operates within ampere range.

3. The fuse rating should always be slightly higher than the current rating in the circuit. If the total load from the battery is 10A, theoretically the rating for the fuse is 125% of the 10A, which is 12.5A. But commercially available fuse with rating closer to the theoretical value is 14A. So the fuse should be rated 14A.

4. Power, P = 500W (given)

Battery Voltage = 12V DC (given)

As per the formula, Power, P = Voltage * Current

Current, I = Power/Voltage = 500/12 = 41.67A

The battery capacity would be , Current * 1 Hour (Assuming the backup is for 1 hour)= 41.67Ah ~ 42Ah

5. The Dom light and the plate light are connected in parallel. The voltage across the devices will be the same and there will not be in drop in intensity of the light. If they were connected in series , the voltage will be different for each and there will be brightness will be different for both. Also, if one of the light is faulty or damaged, the other will function without issues if connected in parallel.

6. The fuse and the starter are connected in series. For series connection, the current is constant across the connected devices. This is necessary for fuse to perform its intended function. It has to blow if the value of current goes higher than rated value. For starter system, maximum current is required for the DC starter motor to function.