ABSTRACT
This chapter describes the basic concepts as well as the various methods and apparati in current use for the measurement of torque and power; the measurement of speed, or more precisely, angular velocity. Torque and power measurements are used in testing advanced designs of new machines and in the development of new machine components. A nonzero resultant torque will cause the body to undergo a proportional angular acceleration, found, by application of Newton's second law, from: where I having units of kilogram meter, is the moment of inertia of the body around the axis. Since drag torque is developed by the motion of the rotor, it is zero at standstill for any value of excitation current. Universal dynamometers are "four-quadrant" machines, a term denoting their ability to produce torque in same or opposite direction as their rotational velocity. Accuracy of power measurement is generally limited by the torque measurement since rotational speed can be measured with almost any desired accuracy.
