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.
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
The luminous efficiency of an electric lamp is the ratio of the luminous flux (in lumen) emitted by the lamp to the electric power (watt) given to it i.e. Luminous efficiency η = Luminous flux/Watt Note:- Lumens is the unit of measurement for luminous flux, which is the total amount of visible light emitted by a source. 1
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.
Mutual inductance between two coupled coils is given by the relation M = K√L1L2 Where L1L2 = Inductance of the coil K = Coefficient of coupling When K = 1 coils are said to be tightly coupled and if K is a fraction the coils are said to be loosely coupled. Here Kmax =1 Kmin =0 ∴ m ≤ (L1 L2 )0.5
Hysteresis Loss = Kh × BM1.67 × f × v watts where Kh = Hysteresis constant depends upon the material Bm = Maximum flux density f = frequency v = Volume of the core Hence the hysteresis loss does not depend upon the ambient temperature.
EXAMIANS
