Question

6. A DC motor coupled to a large grinder develops 120 HP at a constant moment of inertia of the revolving parts is J-2,500 lbft? (a) Calculate the torque [Nm] developed by the motor usin the speed is constant, moment of inertia does not g PnT/9.55 and the fact that when become effective. (b) Calculate the motor torque [Nm] needed so that the speed will increase to 750 rpm in 5s (from 0 to 5 s). Hint: Use the equation : Δη-9.55Tat/J where Δη is the speed difference, at is the time difference and J is the inertia.

Answer 1

Given that DC motor is a electric machine of converting energy Motors take electrical energy and produce mechanical energy. The input is current/voltage and output is torque electric motor are used for power of devices given T = 2,500 lbft^2 (a) formula for the motor power in watts (W) P = nT/9.55 thatis (1) here implies 'P' Is the motor power output (W) implies T is the torque [N M] implies n is the speed of rotation [r/main] implies 9.55 is the constant to take core of units substitute 120 hp for P and 700 VPM for n in equation (1) from equation (1) P = 700T/9.55 thatis (2) implies convert the unit then from horse power [HP] to kilowatt[KW] 1 hp = 1/1.34 KW \r\n 1 HP = 1/1.34 KW use the unit Conversion and rearrange the equation (2) then 120[1/1.34 KW] = 700T/9.55 [since 1 KW = 1000 W] 89352.238 = 700T/9.55 T = 89352.23 times 9.55/700