assign 1 magnetism

A.C. P7 Describe the properties and an application of two different magnetic materials commonly used in electrical and electronic engineering

Task 1

By research and investigation;
a) Identify and name two magnetic materials used in electrical engineering
b) Give an application of each of the two materials
c) Define two of the magnetic properties terms listed below:

B-H curve*, retentivity (a.k.a. remanence), coercivity (a.k.a. coercive force), hysteresis, absolute permeability*, relative permeability*, iron losses. *From Electrical Principles in year 1.
d) Describe the two magnetic properties (defined in c.) of each material in a.

(There are information files on LearnZone that you may wish to use to get you started.)

a.) Iron and stainless steel
b.) Iron is used in power transformers as a core.
Stainless Steel ac motors
c.) retentivity - the ability of a substance to retain or resist magnetization, frequently measured as the strength of the magnetic field that remains in a sample after removal of an inducing field.
Coercivity - The magnetic intensity needed to reduce to zero the magnetic flux density of a fully magnetized magnetic specimen or to demagnetize a magnet. d.)Retentivity -Magnetism that is introduced to iron is only temporary. Once the magnetism is removed then the iron will lose its magnetic strength over a set period of time. Were as magnetism induced in steel is permanent. Coercivity – Iron become demagnetized at 2 oersted Steel become demagnetized at 10,000 H (oe)

http://dictionary.reference.com/browse/retentivity
A.C. P8 Describe the arrangements and features of an electrical supply system from generation through to transmission and distribution to end users

Task 2

By research and investigation describe the arrangements and features of an electrical supply system from generation through transmission and distribution to end users.

You should have images and a description of each stage in the distribution network

from the source of the electrical supply through to the customer.

Include the typical voltage values that are used to distribute the electricity at each stage in the system.

(There are a couple of information files on LearnZone that you may wish to use to get you started.)

First stage is generation of the power this can be done via various means as shown on the diagram on the right.

Second stage – The power that has been generated is carried into a transformer which increases or decreases the voltage to 400,000 volts.

Third stage – A step down transformer, lowers the voltage from 400,000 volts too 132,000 volts.

Forth stage – This is variable depending on where the power is going next if the power is going to heave industry it is lowered to 33,000 volts using a step down transformer. If going to light industry then the power is dropped down to 11,000 volts. Then for household residences the voltage is transformed down to 230volts.

A.C. P9 Describe two different applications of electrical technology and, for each of them, describe how electrical energy is used to enable them to function.

Task 4

a. By research and investigation identify and then describe two different applications of electrical technology.

b. For each of the two examples, describe how electrical energy is controlled and used to enable them to function.

Examples could include:

Manufacturing eg automated processes such as robotics and control systems.

Healthcare eg ultrasound scanners or magnetic resonance imaging (MRI) scanners, operating theatre uninterruptible power supplies (UPS) etc.

Entertainment eg sound and video systems, theme parks, music festivals etc.

Transport eg electric-trains, inner-city trams (The Docklands Light Railway and some airport transport systems have no driver), electric cars, solar powered space travel etc.

Computer psu – a computer power supply has to covert AC current to provide an extremely steady DC current, as the components within a computer are sensitive to changes in voltage (such as cpu, gpu etc.
How does electrical energy used within a psu?
Firstly the electrical energy from the wall socket 220v is inputter into a transformer this will lower it down to a specific value such as 12v. ( a transformer is comprised of a soft iron core wound with two separate coils, one being large ( the one receiving the 220v ) and one being smaller ( the one outputting the 12v ) ). Once this stage has been complete the current will be rectified using diodes. This will convert the ac into pulsating dc current. Next the current is fed through a series of electrolytic capacitors this stored the positive waves and releases them at a discharge point, thus levelling out the pulsating level making a much steadier wave form.

Electric cars – are fully powered by electrical energy, they store this energy and battery’s which in turn power motors that are connected to a drive shaft to turn the cars wheels.
How do electrical cars control the energy and use it?
Firstly the power is stored in lithium-ion batteries the power is fed into these batteries from mains power 220v were it is stored within the battery. This works because the electrons are drawn toward the negative and positive electrodes and separated by a separator. Once the batteries are charged and the car is ready to be moved the power stored inside the batteries travel to the motors. First the power is transported through a rectifier (like the one mentioned is the psu) to convert it to dc then the power is carried along wires that are wrapped along to sides of a magnet one being north one south. Between the two poles is a magnetic rotating rod. When the current flows over the magnets a magnetic field is induced which turns the rotating rod. The rod is then connected to a drive shaft. To increase the speed more current is added thus increasing the magnetic field size.

A.C. M2. Explain the reasons for the use of a range of voltages in an electricity supply system.

Task 3

This is a continuation of P8. Explain why a range of voltages is used such as;

a. 15 to 25kV at the generators and
b. up to 400kV* for transmission
c. and the reasons for other voltages (eg 33kV, 11kV and 3.3kV down to 400/230 volts) for industrial and domestic end users.

*You should include and explain significance of the following two formulae that support the use of high voltage for transmission.
i.e.

and
A.)Generators use this range of voltages mainly because it would be unsafe to go above this level during the generation stage. Most generators have specific rating that they can generate up to (25kv). If generators produced more power it would lead to higher current levels meaning there would be heat losses etc. B.)Voltages of up to 400kv are used for transmission as it reduces the power loss when transmitting over long distances because of the resistance cause by the wires.
So when we look at we can take p as our power lost during transmission. So for us to have least power lost we need a small value of I (amps) so that when we times it by our r we get a small value for p.
So we look at the equation and from this we can identify that to get the same power being transmitted we just need to raise our voltage and low our current.

Power loss - (p=I2xR) & (p=VI)
If we rearrange P=VI to make I=P/V and sub into P=I2xR we get the equation
P=(P/V)2xR

c.)
400/230 volts – This is the value used for household and domestic users. This voltage is chosen because anything over this value would be very deadly. The main reason these voltages are still in place is because it is a standard that cannot be changed as many household appliances work at within the 400/230 volts range.
33,000 volts – This level is used for heavy industry because the machinery and scale of the factories require this power to run.
11kv – light industry used this power levels as it is what the machines require to function, and because of the number off machines.

A.C. D2 Explain and justify how a practical application of electrical technology could be improved by making effective use of available technologies.

Task 5

This is a continuation of P9. Explain and justify how one practical application of electrical technology could be improved by making effective use of available technologies that you may have mentioned in P9. You may use an example that is planned to be implemented in the near future to replace the existing technology or system. You should describe the principle of operation of the new technology and describe how it would be used to improve on the current technology.
Looking at the electrical car we can see that we have to gather power from a mains power supply and once the batteries run out of power the car once again has to be transported back to a mains power supply to recharge. Instead of going back to a mains power supply the car could utilize solar panels. Solar panels could be placed onto the top of the cars roof. Then the power that is generated by them could be fed through a system like in the computer pc (first passing through a transformer to acquire the correct voltage for the motors.) then going through the rectifier. This could eliminate the need for the batteries whilst the sun is shining and power is being generated by the solar panels.

The batteries within the car would also be charged by the solar panels I will explain how this is possible and the process. Below is a picture of the process (Ignore the inverter stage)

process - Light photons hit the solar cells exciting the electrons on the surface, Once the electrons gain enough energy they jump from atom to atom forming a dc current along the surface This energy then flows into a charge controller. A charge controllers governs the voltage entering the battery , it will alter the voltage using capacitors etc. The charge controller is in place because the sunlight can have varying strength, hence different voltages. Once the voltage is even and at the right voltage to enter the battery it does so. With the negative of the solar panel entering and batter at negative and the positive entering the positive.

The solar panels could be placed onto the roof of the car and the wires carrying the current could pass run along the inside body work of the car to the batteries.