Homework_9 - (c) If the terminal voltage is reduced by 25%,...

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O.Tsogbayar Homework Problem A dc shunt motor drives a centrifugal pump at a speed of 1000 rpm when the terminal voltage and line currents are 200 V and 50 A, respectively. The armature and field resistances are 0.1 Ω and 100 Ω, respectively. (a) Designe a starting resistance for a maximum starting current of 120 A in the armature circuit. (b) What resistance should be added to the armature circuit to reduce the speed to 800 rpm?
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Unformatted text preview: (c) If the terminal voltage is reduced by 25%, what is the speed of the motor? Solution a) st a st R R V I + = 5666 . 1 1 . 120 200 =-=-= a st st R I V R b) A I I I f a 48 100 200 50 =-=-= ( 29 1 2 1 add a a a a R R I V R I V n n +--= ( 29 1 1 . * 48 200 1 . * 48 200 800 1000 add R +--= 813 . 1 = add R c) 2 1 2 1 V V n n = 1 2 75 . V V = 750 1000 * 75 . 75 . 1 2 = = = n n rpm...
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