L9 MAGNETIC CIRCUITS ELE 1001 Basic Electrical Technology

L-9 MAGNETIC CIRCUITS

ELE 1001: Basic Electrical Technology Objectives Ø To solve various kinds of problems involving parallel magnetic circuits. Dept. of E&E, MIT, Manipal 2

ELE 1001: Basic Electrical Technology Content • Parallel magnetic circuit Dept. of E&E, MIT, Manipal 3

ELE 1001: Basic Electrical Technology Parallel magnetic circuit Ø More than one path for flux. Ø Total flux Φ is split into Φ 1 and Φ 2 such that Φ = Φ 1+ Φ 1 F A D Φ Φ 1 2 Φ N E B C Analogous electrical circuit Dept. of E&E, MIT, Manipal 1

ELE 1001: Basic Electrical Technology Parallel magnetic circuit with air gap A F Φ 1 E Φ B C Φ 2 D Analogous electrical circuit Dept. of E&E, MIT, Manipal 1

ELE 1001: Basic Electrical Technology Exercise 1 The core shown has a relative permeability of 4000. Find the current required for the exciting coil to produce a flux of 10 milli. Wb in the central limb. Take total number of turns of the coil as 500 turns. Ans: 2. 387 A Dept. of E&E, MIT, Manipal 1

ELE 1001: Basic Electrical Technology Exercise 2 A magnetic circuit made of silicon steel is as shown. The central limb has a cross sectional area of 800 mm 2 and a coil of 500 turns. Each of the side limbs has an area of 500 mm 2. Calculate the magnetizing current required to produce a flux of 1 m. Wb in the 1 mm air gap if μr=1000, length BE = 150 mm; length BAGIDE = length BCHJFE = 250 mm. Neglect leakage factor. B A C G 5 mm H I J 1 mm D E F Dept. of E&E, MIT, Manipal Ans: 2. 04 A 7

ELE 1001: Basic Electrical Technology Summary Ø More than one path for flux in parallel magnetic circuit. Ø Total flux divides into the available parallel paths. Dept. of E&E, MIT, Manipal 8