Explain why the transformers are important in transporting electricity through v

Question

Explain why the transformers are important in transporting electricity through very long distances. Explain briefly how the transformer is used in a car ignition mechanism (spark plug). Given the circuit in figure 4, for which value of the resistive load R_L the dissipated power, of by this load, is maximum? Calculate the power dissipated by the load in function R_1, R_L and V_0 and set the derivative with respect R_L equal to zero (V_0 and R_1 are constant). Why it is difficult to apply the same method to the transformer (in part 2 above)?

Explanation / Answer

1.solution

A transformer doesn't essentialy help directly in transmission of power. It rather acts as a medium to step up or down voltage which is required to efficiently transfer electric power over large distances.

For example: Say power is generated at a voltage of 16 KV .
Now   Power(P) = Voltage(V) * Current(I) * Power factor of load(p.f).
Hence to transmit a fixed amount of power to a certain load ,i.e our P and p.f being fixed , we find transmission at a higher voltage will give us less of current flowing through the transmission wires. Loss in transmission wires is directly proportional to the square of current. Thus less current means less loss. So its economical to step up(increase) the voltage to say 132 KV using a transformer after generation . This is done in the generating substations. After efficient transmission of power , the voltage is stepped down(decreased) to say 33 KV or 416 V by the distribution transformers and then the power is supplied to our homes and various industrial consumers.

2.solution

Transformers are used to step up or step down voltage. The voltage is changed according to the ratio of the turns. Say you have a transformer with 50 turns of wire on the primary and 100 turns on the secondary, a 1:2 ratio. If you put 10 volts into the primary you will get 20 volts out of the secondary. The trick to transformers is that to see anything from the secondary the current of the primary must be changing. If you put a constant DC current through the primary you will have no current flow through the secondary. Transformers are usually used in AC systems since the current is constantly changing. If you put 120 volts AC through a transformer with a turns ratio of 10:1 then you will get 12 volts AC out of the secondary. An ignition coil isn't fed with a constant AC signal. All we need is one spark so all we are going to put into the primary is one voltage spike. An ignition coil typically has a 1:100 turns ratio, so if 10,000 volts is required to generate a spark then we need to feed the primary a 100 volt spike.
    Notice I said if 10,000 volts is required. The required voltage changes constantly. Firing a spark plug outside the engine requires far less voltage than it does when firing an engine at wide open throttle. Pressure plays a major role, the higher the pressure in the chamber the more voltage is required. The size of the spark gap is the other big factor, the further the spark has to jump the more voltage is required. Firing a spark through an air fuel mixture requires more voltage than it would in pure air, especially with exotic fuels. There are many other small factors that determine how much voltage will be required to make a spark. You may see "high performance" coils advertises as 50,000 volt coils but all that is meaningless since under most conditions you will only need 5,000 - 10,000 volts. Now if you are running wide gap plugs in an alcohol burning, supercharged engine then you will likely need to step up to a system with a higher voltage potential.
    So all that's left is to explain where we get the large voltage spike for the primary. The ignition coil may not have changed in the last 100 years but the primary circuit sure has. There are two different types of ignition systems, inductive and CDI. Each system has its strengths and weaknesses. The ignition coil, spark plugs and such are the same between them. The difference is how they generate the primary voltage spike that drives the coil

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.