Solutions to Problems 4-6 and 4-8 in Electrical Engineering, Exercises of Electromechanical Systems and Devices

Download Solutions to Problems 4-6 and 4-8 in Electrical Engineering and more Exercises Electromechanical Systems and Devices in PDF only on Docsity! HOMEWORK 06 - SOLUTION 1. Problem 4-6. [40 points] SOLUTION Since τind = kBR×Bnet, the direction of the induced torques is clockwise- opposite to the direction of motion of the machine. Therefore this machine is acting as a generator. 2. Problem 4-8. [60 points] SOLUTION a. The realtionship between the electrical frequency of the stator fe and the mechanical rate of rotation nm of a magnetic field is given by: nm = 120fe P Using this relationship the following data is tabulated at fe = 25Hz. Number of Poles Mechanical Speed, nm 2 1500 4 750 6 500 8 375 10 300 12 250 14 214.3 The fastest rotation speed was possible at P=2 i.e. 1500r/min. b. The core losses vary as the 1.5th power of the speed of rotation of the magnetic fields i.e. n1.5m Therefore core losses at 25Hz: P = n1.5m = (60fm) 1.5 = (60 ∗ 25)1.5 = 58094 Therefore core losses at 60Hz: P = n1.5m = (60fm) 1.5 = (60 ∗ 60)1.5 = 216000 Ratio: 21600058094 = 3.72 1 docsity.com