Question 4 Refer to our video lab on specifying a DC motor speed measurement. Suppose the motor resistance is 2 ohms, motor inductance is 5 milli-henries, external voltage is 5 volts, and the back EMF time constant is .009 per RPM. As the motor accelerates, what is the motor current in milli-amps at time t = 20 milliseconds when the motor is running at 500 RPM. Ignore any oscillation of the back EMF voltage due to commutation. Type an integer value of milli-amps.
Answers
Answer:
I'm taking a coursera/University of Colorado Boulder course on Motors and there's a question that none of the material covered and the instructors are MIA.
I'm not looking for a straight up answer, but some help in finding the right equations I would need to calculate this. "Final" current seems pretty straight forward at 5V/2ohm = 2.5 amps but I'm not sure how to use the 0.009 per rpm constant to figure out what it would be at t=20ms. Any help would be appreciated!
Suppose the motor resistance is 2 ohms, motor inductance is 5 milli-henries, external voltage is 5 volts, and the back EMF time constant is .009 per RPM.
As the motor accelerates, what is the motor current in milli-amps at time t = 20 milliseconds when the motor is running at 500 RPM. Ignore any oscillation of the back EMF voltage due to commutation. Type an integer value of milli-amps.
Explanation:
Answer:
250 milli-amps.
Explanation:
Taking 0.009 per rpm as voltage. So 500 rpm * 0.009 = 4.5V. So that means that 5V supply - 4.5V back emf = 0.5 V / 2 ohm = 0.25 amps. making 250 milli-amps