It is required to design a DC motor for a small size electric vehicle to be used

Question

It is required to design a DC motor for a small size electric vehicle to be used
inside an airport building to help the transportation of old people. The vehicle
is supposed to carry a maximum of 4 persons at the highest speed of 60
Km/hour. The engine is driven by a 200 V battery bank capable to energize the
motor for 120 Km before being recharged. The efficiency of the motor must be
between 85 to 90 percent. The motor shaft diameter is expected to be within
(0.2 to 0.4 m). Give the size of the battery required in AH (Ampere Hour).
Choose and estimate all the design characteristics of the motor, finally display
all the power flow diagram results including efficiency and speed regulation of
the motor. Give all assumptions taken.

Explanation / Answer

speed = 60kmph
battery bank = 200V

motor works for 120 km before being recharged, so motor would work for 2 hours with 100% efficiency(since speed is 60 kmph and time is 120/60 = 2 hrs = 3600x2 seconds)

efficiency must be 85 to 90%(with 85% efficiency battery would be working for 0.85x2x3600 = 6120 sec)

motor shaft diameter 0.2 to 0.4 m =d = 2 x r
v= r x omega

omega(angular velocity) = v/r= (60 * 5/18) / 0.1 = 166.67 * 60/2 pi rpm = 1592.39 rpm (assume d= 0.2 so r = 0.1)

assume motor draws current of 220mA, then

size of battery required in Ah =?

size of battery will be = 0.85 * .22 * 2 = 0.374 Ah with 85% efficiency

and it will be = 0.9 * .22 *2 = 0,396 Ah with 90% efficiency

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