U3AOS3 Topic 6: Transformers

Transformers are the big HIGH VOLTAGE boxes that you see near powerlines. They are used in order to transmit electricity more efficiently.


If you zoom in on the image you can see a voltage of 22kV. Since this transformer is located in Melbourne it changes the voltage from 22kV to 230V. But how and why do we do this? 


We transport electricity at high voltages to reduce the Power Loss. Electricity at high voltage has a very low current due to 

P=IVP=IV



Transformers are designed through the following ratio. The N stands for the number of loops on each side. Since the power is a fixed value, the voltage and currents will change.

N1N2=V1V2=I2I1\frac{N_1}{N_2}=\frac{V_1}{V_2}=\frac{I_2}{I_1}

The left side of the transformer is generally the primary side followed by the box and then the secondary side.

There are 2 types of conversions that occur:

Step up: Where there are more secondary coils than primary coils

Step down: where there are more primary coils than secondary coils.

 

NOTE: ONLY AC POWER CAN BE TRANSFORMED. THIS IS BECAUSE THE AC CURRENT INDUCES A CURRENT THROUGH THE METAL SQUARE.


Use the simulation below to assist you. In this Np,VpN_p, V_p stands for the primary and Ns,VsN_s, V_s stands for the secondary. 

Created with GeoGebra®, by Tan Seng Kwang, Link