r ceramic magnets are not easily demagnetised magnetized and hence find wide application in such appliances. br/>
4.4.2 Properties of the loudspeaker magnet
According to its nameplate the speaker that used the magnet in figure 4.3 had a 0.5W rms and an impedance of 8 ohm. The magnet type on the loudspeaker is a ferrite [Refer to appendix D1]. The manufacturer of the magnet on the speaker is traced in order to find the BH properties of the magnet on the speaker. p> Appendix D2 indicates TDK datasheet for ferrite magnets FB series. These notes were used to find the magnetic, physical and mechanical characteristics of the magnet. The properties of the loudspeaker are summarized in table 4.3. br/>
Magnet
Type
B r (T)
Hc (kA/m)
Ferrite
FB5N
0.43
214.9
Table 4.3 Summarized properties of the magnet speaker
4.4.3 Output EMF and flux of the recyclable generator
The properties were modelled in FEMM, and the generator outputs are tabulated in table 4.4. Refer to appendix B2 for the graphs of the outputs.
Loudspeaker Magnet
Flux (Rms)
EMF (Rms)
Ferrite
0.0171
3.4987
Table 4.4 Generator output with the loudspeaker magnet
В
4.5 The estimated output power of the generators
The output electrical power of a generator is given by:
(Eq. 4.1)
where V is the terminal voltage of the machine. The power factor is assumed to be unity for these calculations since all the simulations and investigations are done at no-load.
From the rated power of the generator which is 36W. If the rated voltage is assumed to be 12 V then the rated current of the generator can be calculated from equation 4.1 to be 1A. p> Table 4.2 and 4.3 above gives the results of the simulated induced voltages and flux obtained from the generator with commercial and recycled magnets. Using the 1A above as the rated current, the output power of the generator using commercial magnets and recycled loudspeaker magnets is summarized in table 4.5 below. The output power in all the cases is calculated from equation 4.1.
Magnet
Type
Output Power
Rare-Earth
NdFeb32
28.3W
Alnico
Alnoco5
15.5W
Ceramic
Ceramic8
10.8W
Ceramic
Speaker magnet
10.5W
Table 4.5 The output power of the generator
Chapter 5. Analysis of the generator outputs
In this chapter the author first began by analysing the output power of the generator designed with commercial magnets and the one with recycled loudspeaker magnets. The author then explored the factors that may have affected the outputs from the recycled generator. p> The terminal voltage induced from the recycled generator is also explored to view if it can be used in any applications in the rural village. This is done so that the voltage can be evaluated if it is useful or not
Lastly the loudspeaker magnets are investigated to view how they can be used in the recycled generator design; whether they should be smashed and aligned to be re-used in the generator design or if they should be used the way they are without being smashed. br/>
5.1 The estimated output power of the generators
The output power of the generators is estimated from the output induced voltages of the generators. Consequently, this means that the higher the terminal voltage of the generator the larger the output power.
From the theory of magnets it is clear that the induced voltage is directly proportional to the remanent magnetic flux density Br of a magnet. In other words it is expected that rare-earth magnets which posses higher Br will always induce high voltage when used in generators. Therefore it can be said that the type of magnet used in a generator is very important as it determines the output power of the generator.
As can be seen from the results, the induced voltage of the ...
