Indepth Electrical engineering

Skin Effect in Transmission Lines: Meaning, Causes & Factors What is Skin Effect? Skin effect is a phenomenon that occurs in transmission lines carrying alternating current (AC) , where the current is not uniformly distributed across the entire cross-section of the conductor. Instead, the current density is higher near the surface (or skin ) of the conductor and much lower at the core. In contrast, direct current (DC) flows uniformly throughout the cross-section of the conductor, hence skin effect does not occur in DC systems. This uneven distribution of AC leads to an increase in effective resistance of the conductor compared to DC. Why Does Skin Effect Occur in AC? The root cause of skin effect lies in the electromagnetic flux linkages created by alternating current: The inner filaments of the conductor produce flux that links with both inner and outer filaments . The outer filaments, however, only produce flux that links with themselves. This means flux link...

⚡ Corona Effect in Transmission Lines 🔹 Introduction In high-voltage transmission lines , the surrounding air acts as a dielectric medium. When the electric field intensity around conductors exceeds a certain critical value , it ionizes the surrounding air molecules. This ionization leads to partial discharge of electricity , accompanied by bluish glow, hissing noise, and ozone production. This phenomenon is known as the Corona Effect . 🔹 Mechanism of Corona Formation Free electrons are always present in air (from cosmic rays, UV radiation, radioactivity). As voltage increases → electric field gradient at conductor surface increases. Electrons accelerate → collide with neutral air molecules → release more electrons. This leads to an electron avalanche → ionization of surrounding air. Discharge appears as faint luminous glow + hissing sound . 👉 If conductor spacing is too small (spacing-to-radius ratio < 15), flashover occurs before corona starts . 🔹...

Torque Equation of Induction Motor: Explained with Factors Affecting Speed-Torque Characteristics Induction motors are widely used in industries due to their robustness, low cost, and simple construction. One of the most important aspects of analyzing an induction motor is its torque equation , which helps in understanding how the motor develops torque under different operating conditions. Torque Equation of an Induction Motor The general torque equation of an induction motor is: T = 3 ω s ⋅ V 2 ⋅ R 2 ′ s ( R 1 + R 2 ′ s ) 2 + ( X 1 + X 2 ′ ) 2 T = \frac{3}{\omega_s} \cdot \frac{V^2 \cdot \frac{R_2'}{s}}{(R_1 + \frac{R_2'}{s})^2 + (X_1 + X_2')^2} Where: T = Torque developed V = Applied stator voltage per phase R1 = Stator resistance R2’ = Rotor resistance (referred to stator side) X1 = Stator reactance X2’ = Rotor reactance (referred to stator side) s = Slip ωs = Synchronous angular speed Key Relation: Torque is Proportional to ...

Starting Of Slip Ring Induction Motors Slip ring Induction motors had external resistance connected in line. These motors are usually started with full line voltage applied across its terminals. During starting of slip ring induction motors the value of starting current is adjusted or kept minimum, by increasing the resistance of the rotor circuit.  The external resistance is connected in star and kept at maximum during starting so to minimize starting current. By increasing the rotor resistance it will not only reduces the rotor current but the stator current too. This means that whenever a resistance is added in rotor circuit that will leads to reduced starting current. Thus because of this, the starting torque is increased due to the improvement in power factor. Usually resistance is added during starting and slowly made out of circuit when motor attains the speed and this resistance is disconnected by using a contactor in line.  Slip ring can be taken in...

Comparison of Motor Starters: Advantages and Disadvantages Motor starters are essential in controlling the starting current, voltage, and torque of induction motors. Each type of starter has its own application area, benefits, and limitations . Below is a detailed comparison of commonly used starters: 1. Direct-On-Line (DOL) Starter Advantages Very simple design and operation . Low maintenance due to minimal components. Low initial cost . Ease of installation with straightforward circuitry. Suitable for small motors (up to ~10 kW) . Disadvantages Very high inrush starting current (6–8 times full load current). Causes voltage dips in weak supply systems. Not suitable for larger motors (>10 kW) . No power saving during operation. Short acceleration period , making it unsuitable for heavy loads. 2. Star-Delta Starter Advantages Reduces starting current to about 1/3 of DOL value . Prov...