2 A Dc Shunt Motor Has The Armature Resistance Of 0 05 22 And The Field Winding Resistance Of 10 12 The Motor Is Coupl 1 (74.89 KiB) Viewed 50 times
Question 3(b)
2 A Dc Shunt Motor Has The Armature Resistance Of 0 05 22 And The Field Winding Resistance Of 10 12 The Motor Is Coupl 2 (20.82 KiB) Viewed 50 times
2. A DC shunt motor has the armature resistance of 0.05 22 and the field winding resistance of 10 12. The motor is coupled to an overhauling load. The values for magnetisation curve in Table 1 were measured at 600 rpm and the motor is braked by a self-excited dynamic braking with a braking resistance of 1 2. a) Extend the values in Table 1 for armature current (Ia), field constant (Kø) and torque (T). Provide the equivalent circuit and equations involved. b) Find the field current required to hold the load if the overhauling load has a torque of 450 Nm. c) Calculate the speed of the motor that will hold the load in Question 3 (b). d) If the motor is required to hold the load in Question 3(b) at the speed of 1200 rpm. i) Provide the corresponding table for the new speed. ii) Calculate the value of the dynamic resistance, RB at If = 25 A. e) Discuss the power dissipated during the dynamic braking. Use the related previous values for Rg to demonstrate your point. Table 1 2.5 5 7.5 5 10 12.5 15 17.5 20 22.5 Field current, A Back emf, V 25 25 50 73.5 90 102.5 110 116 121 125 129
b) The starting time of a DC shunt motor in a high-performance application must be limited to 2 seconds. The motor has a moment of inertia of 3 Nm-secand the load moment of inertia is 6 Nm-sec2. The field constant of the motor is 3 V-sec and the armature resistance is 12. Show how the desired starting time can be achieved.
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