EET221: Magnetic Materials and Circuit Tutorial 2

EET221: Magnetic materials and circuit Tutorial 2

1. The long solenoid coil shown in Figure 2 has 250 turns. At its length is much greater than diameter, the field inside the coil may be considered uniform. Neglect the field outside. a) Determine the field intensity (H) and flux density (B) inside the solenoid (i =100A). b) Determine the inductance of the solenoid coil. c) Find the current I in the coil to produce a flux (Φ) = 0.012 W (Hint: Just used the available formulas)

Figure 1

2. The toroidal core shown in Figure 2 is made from cast steel. a) Calculate the coil current required to produce a core flux density of 1.2T at the mean radius of the toroid. b) What is the core flux? c) If a 2mm wide air gap is made in the toroid (across A-A'), determine the new coil current required to maintain a core flux density of 1.2T. (Hint: Find H from Figure 3,)

Figure 2 EET221: Magnetic materials and circuit Tutorial 2

Figure 3

2. A ferromagnetic core is shown in Figure-1. The depth of the core is 5 cm. The other dimensions of the core are as shown in the figure. Find the value of the current that will produce a flux of 0.005 Wb. With this current, what is the flux density at the top of the core? What is the flux density at the right side of the core? Assume that the relative permeability of the core is 1000. (Hint: Identify number of different region and represent it as reluctance, find its mean path length)

Figure 4 EET221: Magnetic materials and circuit Tutorial 2

3. A core with three legs is shown in Figure 5. Its depth is 5 cm, and there are 200 turns on the leftmost leg. The relative permeability of the core can be assumed to be 1500 and constant. What flux exists in each of the three legs of the core? What is the flux density in each of the legs? Assume a 4% increase in the effective area of the air gap due to fringing effects.

Figure 5