Motor and Motor Control Circuits Week 4 Quiz Answers Coursera

Motor and Motor Control Circuits Week 4 Quiz Answers

1. In the video on "Illustrative example of a stepper motor drive" we showed you a stepper motor that rotated 90 degrees clockwise. How would you alter the sequence of energizing and de-energizing the coils in the first step to make the stepper motor run counter-clockwise?

De-energize Phase 1 and energize Phase 2 South North

2. What is the definition of a phase in a stepper motor?

A pair of windings on opposite sides of the rotor, one magnetic North and the other magnetized South

3. Which of the following are disadvantages of using a stepper motor relative to a DC motor? Select all that apply.

You need to purchase motor driver circuitry, or design your own and write custom firmware

4. What happens if you provide double the rated voltage to a stepper motor?

The speed and torque both increase, but by less than double

5. Which statement below correctly describes the difference between a unipolar drive and a bipolar drive for a stepper motor? Select all that apply.

In a unipolar drive current flows through the winding solely in one direction, while in a bipolar drive it flows in both directions

A bipolar drive will give you much higher torque output than a unipolar drive

6. What is true about the torque output of a stepper motor?

The torque output varies throughout each step

7. How would you compare the acceleration of a stepper motor to other DC motors, assuming voltage and current inputs are equivalent? Select all that apply.

The stepper motor accelerates slower because it has much more inductance than other DC motors

The stepper motor accelerates slower because its rotor has much more mechanical inertia than other DC motors

The stepper motor accelerates slower because of the delay in having current ramp up and down in each coil as the motor steps

8. What do the bipolar motor drive made of discrete components that we studied in the video bipolar driver chip that we in common?

"Stepper Motor Specs and Operation" and the commercial studied in the video "Commercial Stepper Motor Driver Chips" have? 

Both of them contain H- bridge transistor networks

9. How does the torque speed curve of a stepper motor compare to that of other DC motors?

Torque increases as speed increases for both stepper motors and other DC motors<<<wrong 

10. Suppose you are building a machine where the timing sequence of two drive axes requires that they operate at precisely the same speed. What type of motor would you select: AC or DC and why?

You select identical DC motors because controlling voltage input gives simple and precise speed control