EEE-1.pptx.pdf

Elements of Electrical Engineering (EEE) B. Tech. Sem I (CH/CL/IC/MH) Syllabus to be covered TRANSFORMERS Magnetic materials, BH characteristics, ideal and practical transformer, equivalent circuit, losses in transformers, regulation and efficiency. Auto- transformer and three-phas...

Elements of Electrical Engineering (EEE) B. Tech. Sem I (CH/CL/IC/MH) Syllabus to be covered TRANSFORMERS Magnetic materials, BH characteristics, ideal and practical transformer, equivalent circuit, losses in transformers, regulation and efficiency. Auto- transformer and three-phase transformer connections. ELECTRICAL MACHINES Generation of rotating magnetic fields, Construction and working of a three- phase induction motor, Significance of torque-slip characteristic. Loss components and efficiency, starting and speed control of induction motor. Single-phase induction motor. Construction, working, torque-speed characteristic and speed control of separately excited dc motor. Construction and working of synchronous generators Text Books: 1. Basic Electrical, Electronics and Computer Engineering, R. Muthu Subramanian, S. Salivahanan, K. A. Muraleedharan, 2ndEdition, Tata McGraw Hill 2. Principles of Electronics, V. K. Mehta & Rohit Mehta, 11th Edition, S. Chand & Company 3. Electrical Technology (Vol: II), B. L. Theraja , A. K. Theraja, 23rdEdition, S. Chand & Company 4. Basic Electrical Engineering, D.P. Kothari, I. J. Nagrath, 3rd Edition, Tata McGraw Hill Magnetic Materials Contents Terms Connected with Magnetic Circuits Classification of Magnetic Materials BH Curve & Hysteresis Terms Connected with Magnetic Circuits Magnetic Flux (φ) : The magnetic lines of force produced by a magnet is called magnetic flux. Its unit is Weber. 1 wb = 108 magnetic lines = 108 Maxwells   COMPARISON BETWEEN MAGNETIC & ELECTRIC CIRCUIT Sr. Magnetic Circuit Electric Circuit No. 1 The closed path for magnetic flux The closed path for electric current is is known as magnetic circuit. called an electric circuit. 2 Flux = MMF / Reluctance Current = EMF / Resistance 3 MMF (A) EMF (V) 4 Reluctivity Resistivity 5 Reluctance Resistance 6 Permeance = 1 / Reluctance Conductance = 1 / Resistance 7 Flux Density, B (w/m2) Current Density, J (A/m2) 8 Magnetising force, H Electric field intensity, E Introduction Magnetic materials are those materials in which a state of magnetization can be induced. In other words, the materials which can be magnetized are known as Magnetic Materials. Classification To study magnetic properties of magnetic materials, the material is usually placed in a uniform magnetic field. Paramagnetic Materials Diamagnetic Materials Ferromagnetic Materials  Paramagnetic Materials The materials which are not strongly attracted to a magnet are known as paramagnetic material. Their relative permeability is small but positive Such materials are magnetized only when placed on a super strong magnetic field and act in the direction of the magnetic field. Since, the orientation of the dipoles parallel to the applied magnetic field is not complete, the magnetization is very small. Examples: aluminium, titanium, sodium, oxygen, magnesium etc Diamagnetic Materials The materials which are repelled by a magnet Their relative permeability is less than unity. They are slightly magnetized when placed in a very strong magnetic field and act in the direction opposite to that of applied magnetic field. Examples: Gold, Silver, Water, Bismuth etc. Ferromagnetic Materials The materials which are strongly attracted by a magnetic field or magnet is known as ferromagnetic material. More magnetized in the direction of field. The relative permeability of these materials is very high. Examples: Iron, Steel, Nickel, Cobalt etc. What is magnetizing field (H), Intensity of Magnetization (I), and resultant magnetic field (B) ? First there is just a material ‘X’ in space then we apply a Magnetizing Field (H) on it. As a result, the material gets magnetized and the magnetic moment developed per unit volume is Intensity of Magnetization (I). The resultant magnetic Field (B) inside the material is the sum of the applied magnetic field and the magnetic field due to magnetization. B = µ0 (H+I) What is Magnetic Susceptibility? For paramagnetic and diamagnetic substances, the intensity of Magnetization (I) of a material is directly proportional to the magnetic intensity (H). This proportionality constant is called Susceptibility of the material. Define Permeability of a Magnetic substance? It is the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization that a material obtains in response to an applied magnetic field. BH Curve What is a Hysteresis curve? When an external magnetic field is applied to a ferromagnetic material, then it gets magnetized. The magnetization in the material increases with the increase in the Magnetizing Field. But, when all the domains in the material get align with the magnetizing field then the material can not be magnetized further. And meets a saturation magnetization. Now, even if we remove the magnetic field, the magnetizations will not get back to zero. And we need to apply a reverse magnetic field to nullify it. A saturation magnetization can also be achieved in reverse direction. In this cycle a loop is obtained which is called as Hysteresis loop. What is Retentivity? It is the magnetization left in the material after the removal of the magnetizing field. What is Coercivity? It is a measure of the reverse magnetization to demagnetize the retentive field of the material.  The dictionary meaning of hysteresis is ‘delayed’, here it is the magnetic induction B, which is lagging the magnetizing field H.