Question $4$

Given that you have to develop an electric drive for a three$-$wheel Tuk$-$Tuk which will be used to move people

from the Wits main campus to the education campus in Park Town. The Tuk Tuk can only carry a maximum

of two people at a time and can reach its maximum speed of $60$k$($m$)/($h$)$r in $10$ sec $.$ It has a wheel radius of $250$

mm $.$ Assume transmission efficiency is $100\%$ and the transmission ratio is $1\mathrm{.}5.($Ignore road gradient and all

the drag forces on the vehicle$)[$hint: average weight of passenger is $65$ kg $]$

Given that T$\_($m$)=(($F$\_($x$))/(\backslash$eta $\_($T$)))(($r$\_($w$))/($n$\_($d$)))$ is the motor torque and $\backslash$omega $=$n$\_($d$)(($v$)/($r$\_($w$)))$ is the motor shaft speed in ra$($d$)/($s$)$

where F$\_($x$)=$Ma$,$ is the traction force on the wheels $($M$,$ mass and a acceleration$),$ r$\_($w$)$ is the wheel radius,

n$\_($d$)$ transmission ratio, $\backslash$eta $\_($T$)$ the transmission efficiency and v linear speed in $($m$)/($s$).$

$($a$)$ Provide a torque speed and a power speed curve $($with key values$)$ on the same plot, suitable for

the application described above $($e$.$g$.$ base speed, max torque, etc$)$

$($b$)$ Provide a typical diagram of the electric drive system for the electric Tuk$-$Tuk and explain

purpose of each component

$($c$)$ What type of electric machine would you choose for this application?

$($d$)$ Provide at least four reasons for the choice made in $($c$)$

N$.$B: List all the assumption made