282581934 by Unknown

Author:Unknown
Language: eng
Format: epub

FIG. 3.39

where ω is the speed of the brake drum in rad/s mechanical and the torque, T = Wr newton metres. W is the reading in newtons on the balance and r metres is the perpendicular distance from the centre of the brake shaft to the line of action of the balance.

An alternative method of measuring the torque is illustrated in Fig. The brakes described above are only suitable for measuring the output torque of small machines having a steady power output.

Another type of dynamometer consists of a separately-excited d.c. generator whose stator casing is mounted on trunnion bearings and so is free to rotate between predetermined limits. A lever arm extending from the casing connected to the balance, enables the torque to be measured. The load on the driving machine may be varied by either altering the value of the load resistor connected to the armature circuit or by varying the voltage generated by altering the field circuit excitation. This type of dynamometer can handle a much greater power than the brake type and it is easier to obtain satisfactory readings.

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