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Torque and Power

Table 1 shows a set of torque-speed measurements for a d.c. electric motor intended for use in an electric wheelchair. Data of this type is used by manufacturers to help specify motor performance.

Table1
Speed /rpm..............600..........1200......1850..........2400.......3050.........3700
Torque /Nm..............5.51..........4.53.......3.75..........2.94........2.09.........1.08

(a) Use the data in Table 1 to plot a suitable graph and obtain the five missing pieces of information, labelled (i)-(v), in the motor specification chart shown in Table 2.

Table 2
.................Stall....................No Load................Maximum Efficiency (Effic)
Operating
Volt /V.......Torque...Current....Speed.....Current...Torque....Speed...Current...Output
................./Nm....... /A.........../rpm ......./A......... /Nm....../rpm....... /A......(Effic)/%

24................(i)........140............(ii)..........5.2.........(iii).......4000.......(iv).........(v)

(b) One of the design requirements for the wheelchair states that the motor must be able to supply 40 Nm of torque at 100 rpm. Determine whether this particular motor has the power to meet that requirement.

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Solution Preview

Speed /rpm Torque/Nm
0 6.31
600 5.51
1200 4.53
1850 3.75
2400 2.94
3050 2.09
3700 1.08

4000 0.717

slope = -0.001
y intercept 6.31

y = -.001x + 6.31

y = -.001 ( 4000) + 6.31
0.717
y= -.001 (5000) +6.31
-0.04

The torque of motor is proportional to the current
flowing through it ( T = i)

The angular velocity of motor is proportional to the voltage across ...

Solution Summary

Electric chair are power by motor that used a specified power and torque. These are the step on how to calculate torque and angular speed.

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