The ratio of luminous flux leaving the surface (Reflected Light) to the luminous flux incident on it (Incident Light) is known as the reflection factor. Reflection Factor = Reflected light/Incident light The value of the Reflection factor is always less than 1.
The shaded-pole motor is the original type of AC single-phase induction motor. Shaded pole-type single-phase induction motors are provided with shading rings on their poles which are the projected type of poles. The stator of such motors has projected poles like DC machines as shown in Fig. 5.7. The rotor is a squirrel cage type similar to that of split-phase-type motors. The poles are excited by giving a single-phase AC supply. A single-turn thick coil in the form of a ring called the shading ring is fitted on each side of every pole as shown. The portion of the poles where the shading ring is fitted is called the shaded portion, while the other portion is called the unshaded portion. The shaded pole motor has the lowest starting torque as compared to the all single-phase induction motors.
By the term, torque is meant the turning or twisting moment of a force about an axis. It is measured by the product of the force and the radius at which this force acts. Consider a pulley of radius r meter acted upon by a circumferential force of F Newton which causes it to rotate at N r.p.m. The angular speed of the pulley is ω = 2πN/60 rad/sec Work is done by this force in one revolution = Force × distance = F × 2πR Joule The power developed = Work Done/Time = (F × 2πR)/60/N = (F × R) × (2πN)/60 The power developed = T × ω watt or P = T ω Watt pmech = (ωT)
The average value of the sine wave over one complete cycle is actually zero. Hence, for a sine wave, the average value is defined over half the period. The average value expressed in terms of peak value is given by Average value = 0.637 × peak value
EXAMIANS
