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Problem solutions: Chapter 7

tài liệu Problem solutions: Chapter 7 sau đây. Tài liệu dành cho các bạn học chuyên ngành Điện. Tham khảo nội dung tài liệu để nắm bắt nội dung chi tiết. | 85 PROBLEM SOLUTIONS Chapter 7 Problem 7.1 part a wm x Va. part b wm x If part c wm will be constant. Problem 7.2 part a For constant terminal voltage the product nIf where n is the motor speed is constant. Hence since If x 1 Rf Rỉ Rf 5 1180 1250 and hence Rf 84.2 Q. part b 1380 r min Problem 7.3 Check this part a wm halved Ia constant part b wm halved Ia doubled part c wm halved Ia halved part d wm constant Ia doubled part e wm halved Ia reduced by a factor of 4. Problem 7.4 part a Rated armature current 25 kW 250-V 100 A. part b At 1200 r min Ea can be determined directly from the magnetization curve of Fig. 7.27. The armature voltage can be calculated as Va Ea Ia Ra and the power output as Pout VaIa. With Ia 100 A If A Ea V Va V Pout kW 1.0 150 164 16.4 2.0 240 254 25.4 2.5 270 284 28.4 part c The solution proceeds as in part b but with the generated voltage equal to 900 1200 0.75 times that of part b If A Ea V Va V Pout kW 1.0 112 126 12.6 2.0 180 194 19.4 2.5 202 216 21.6 Problem 7.5 part a Mil Power kW 87 Problem 7.6 part a Pshaft Ea Va - Ea Ra and thus Ea Va wVa2 - 4PshaftRa 2 The motor speed n can then be found from n 1200 f Ea 1.67 X 1200 r min Here is the desired plot produced by MATLAB part b The solution for Ea proceeds as in part a . With the speed constant at 1200 r min and hence constant wm solve for If as If K where Kf 150D V A. Here is the desired plot produced by .