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PN Junction Diode

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  PN Junction Diode  1. Basic Concept A PN junction diode is formed by joining p-type and n-type semiconductor materials into a single crystal. Its key property is unidirectional conduction : it conducts current mainly in one direction and blocks it in the other. 2. Doping and Charge Carriers P-type Semiconductor Doped with trivalent impurities (Boron, Gallium) Majority carriers: holes Minority carriers: electrons N-type Semiconductor Doped with pentavalent impurities (Phosphorus, Arsenic) Majority carriers: electrons Minority carriers: holes 3. Formation of the PN Junction When P-type and N-type materials are joined: 3.1 Diffusion Process Electrons diffuse from N → P Holes diffuse from P → N They recombine near the junction 3.2 Depletion Region Mobile charge carriers disappear near the junction Leaves behind fixed ions This region is called the depletion layer 3.3 Electric Field Formation Positive ions on N-side...
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polarity test of transformer

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Current flows from a high voltage point to a low voltage point because of the potential difference . Electrical polarity describes the direction of this current flow. In a DC system, one pole is always positive, and the other is negative, so the current flows in one direction. In an AC system, the terminals change polarity periodically, changing the direction of the current. We use dot convention to identify the voltage polarity of the mutual inductance of two windings. The two used conventions are: If a current enters the dotted terminal of one winding, then the voltage induced on the other winding will be positive at the dotted terminal of the second winding. If a current leaves the dotted terminal of one winding, then the polarity of the voltage induced in the other winding will be negative at the dotted terminal of the second winding. Distribution transformers need to operate continuously and handle high demand during peak times. To manage this, we connect transformers i...
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Torque in 3 phase induction motor

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  Torque in a 3 phase induction motor  is determined by three key factors: Firstly the magnitude of rotor current, secondly the flux which interact with the rotor of three phase induction motor and is responsible for producing emf in the rotor part of inuction motor, lastly the power factor of rotor of the three phase induction motor. By integrating these factors, we derive the torque equation as follows: Where, T is the torque produced by the induction motor, φ is flux responsible for producing induced emf, I 2 is rotor current, cosθ 2 is the power factor of rotor circuit. The flux φ produced by the stator is proportional to stator emf E 1 . i.e φ ∝ E 1 We know that transformation ratio K is defined as the ratio of secondary voltage (rotor voltage) to that of primary voltage (stator voltage). Rotor current I 2 is defined as the ratio of rotor induced emf under running condition , sE 2 to total impedance, Z 2 of rotor side, and total impedance Z 2 on ...
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Double Revolving Field Theory for single phase induction motor

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  Operating Principle of Single-phase Induction Motor A Single phase induction motor consists of a squirrel cage rotor and a stator carrying a single-phase winding. When a single-phase AC supply is fed to the stator winding, a pulsating magnetic field (not the rotating) is produced. Under these conditions, the rotor does not rotate due to inertia. Hence, a single-phase induction motor is inherently not self-starting, but requires some auxiliary starting means. If the stator winding of a single-phase induction motor is excited and the rotor is rotated by an auxiliary means and the starting device is then removed, the motor continues to rotate in the same direction in which it is started. The double revolving  field theory  is suggested to analyse the performance of a single-phase induction motor. It explains why a torque is produced in the rotor once it is turning. Double Revolving Field Theory According to the double revolving field theory of single-phase i...
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