The performance of a radio receiver is measured on the basis of its selectivity, sensitivity, fidelity and image frequency rejection. Selectivity The selectivity is the ability of the receiver to select a signal of a desired frequency while rejecting all others. The selectivity of the receiver is obtained partially by RF amplifier and mainly
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The problems of TRF receiver are overcome in this receiver. The superheterodyne receiver converts all incomming RF frequencies to a fixed lower frequency, called Intermediate Frequency (IF). This IF is then amplified and detected to get the original signal. Fig shows the block diagram of superheterodyne receiver. The antenna receives all the frequency signals and
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Fig shows the block diagram of Tuned Radio Frequency TRF receiver. The received signal is weak and noisy. It is given to broadband RF amplifier. The RF amplifier enhances signal to noise ratio and amplifies the signal. It is then passed through AM detector. The output of AM detector is audio signal. The detected
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3Φ AC synchronous motor Revolving armature type Revolving field type Conventional 3Φ Synchronous Motor : (Revolving Field Type) Stator : Stator is made up of silicon steel stampings. Stator slots carry a balanced 3Φ armature winding, wound for a specified even number of poles. The ends of the armature windings are connected to the terminals
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Merits of SRM Construction is simple and robust. Rotor carries no windings, no sliprings, no brushes, less maintenance. There is no permanent magnets. Ventilating system is simpler as losses takes place mostly in the stator: Power semi conductor switching circuitry is simpler No shoot through fault likely to happen power short circuits. Developed torque doesn’t
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SRM is a single excited and double salient pole electric motor. It is an electromagnetic and electrodynamic equipment. Switched reluctance motor operating principle is similar to a single-stack variable-reluctance stepping motor. However, design procedures and control strategies in VRM are different from those used in a stepping motor. For example, a SRM requires a rotor
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Figure shows evolution of brushless dc motor. Conventional DC Motor The first stage of evolution of DC motor is conventional type DC motor. It is an electro magnetic and electro dynamic equipment. Sator Stator is made up of forced steel with inward projected poles. The poles carrying field windings. The field windings are connected such
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It is a signal phase motor whose operation depends upon the hysteresis (magnetisation produced in a ferromagnetic material lags behind the magnetising force) and on the presence of continuously revolving magnetic flux. Construction A stator designed to produce a synchronously revolving field from a single phase supply. This is accomplished by using permanent split capacitor
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A universal motor is a specially designed series wound motor, that operates at approximately the same speed and output on either dc or ac of approximately same voltage. Construction A universal motor is similar to a de series motor in construction. It is constructed with few series field turns, laminated armature and field circuits, low
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Repulsion motor are similar to series motors except that the rotor and the stator windings are inductively coupled, the rotor current is obtained by transformer action from the stator. Types of Repulsion Motor Two stator winding repulsion motor Compensated repulsion motor. Repulsion start induction motors. Repulsion induction motors. Repulsion Motor Repulsion motors is similar to
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