ME 337 Motor Homework Due in class on Sept.29,2014 CID: NAME: Problem 1: What type(s)of electric motor would you specify? a)To drive a load with large inertia. b)To minimize variation of speed with load variation To maintain accurate constant speed regardless of load variations. Problem 2: Refer to the AC motor performance curve in the following figure. a)What type of motor is the curve likely to represent? b)If the motor is a six-pole type,rated at 0.75 hp,how much torque can it exert at the rated load? ) How much torque can the motor develop to start a load? d What is the breakdown torque for the motor? 100 80 60 40 20 0 0 100 200 300 400 Torque (percentage of full-load torque) Problem 3: Three examples of motors,with their parameters are listed in the Table below.For each case pick the best motor. a)A rotary load with a moment of inertia of 0.02 Kg m2 is driven by a gear reducer. Select the motor that produces the minimum power dissipation and the motor that results in minimum temperature rise.Find the optimal gear ratio in either case. b)A mass of M=0.75 Kg must be driven by a pulley.Select the motor that can drive it under minimum temperature rise and find the optimal radius size
ME 337 Motor Homework Due in class on Sept. 29, 2014 CID: NAME: Problem 1: What type(s) of electric motor would you specify? a) To drive a load with large inertia. b) To minimize variation of speed with load variation. c) To maintain accurate constant speed regardless of load variations. Problem 2: Refer to the AC motor performance curve in the following figure. a) What type of motor is the curve likely to represent? b) If the motor is a six-pole type, rated at 0.75 hp, how much torque can it exert at the rated load? c) How much torque can the motor develop to start a load? d) What is the breakdown torque for the motor? Problem 3: Three examples of motors, with their parameters are listed in the Table below. For each case pick the best motor. a) A rotary load with a moment of inertia of 0.02 Kg m2 is driven by a gear reducer. Select the motor that produces the minimum power dissipation and the motor that results in minimum temperature rise. Find the optimal gear ratio in either case. b) A mass of M = 0.75 Kg must be driven by a pulley. Select the motor that can drive it under minimum temperature rise and find the optima1 radius size
Table ll-Motor Parameters Parameter Motor兰1|Motor兰2 Motor #3 Motor Parameters Torque constant K [N-/A] 0.1 0.2 0.25 Moment of inertia Im [K.m2 2105 3-105 1-103 Armature resistance r (2] 2 1.25 Continuous torque Ta IN】 0.5 2.2 6.2 Derived parameters Electromechanical time 0.004 0.001 0.002 constant tm (s] Power rate Tc2/Im [ 12,000 31,000 38,000 Problem 4: A rotating antenna has a moment of inertia(I)of 0.8 Ib ft s2.It is driven through a 10: 1 gearbox by a DC motor(motor runs faster).The antenna must be able to rotate 180 degrees from rest in 1 s.The motor characteristics are given below.Find the motor voltage required. 500 400 300 -12V 5V 5V 100 0 50 100L118150 Torque(0n.·oz) LLLLL1L1LL 0.5 .0 Torque(N·m)
Problem 4: A rotating antenna has a moment of inertia (I) of 0.8 lb ft s2 . It is driven through a 10: 1 gearbox by a DC motor (motor runs faster). The antenna must be able to rotate 180 degrees from rest in 1 s. The motor characteristics are given below. Find the motor voltage required. m Tc 2 / Im m
