Solution Manual for Introduction to Mechatronic Design Do Not Circulate
Chapter 25 Brushless DC Motors
25.1) How do the terminal-to-terminal inductances compare between a Wye-connected and a delta-connected
motor?
25.2) How would you expect the difference in inductance between a Wye-connected and a delta-connected
motor to be manifested in the performance of the motor? Describe the differences in expected performance.
25.3) What is the relationship between mechanical and electrical degrees for a BLDC motor with 48 internal
poles?
25.4) If the coils in Figure 25.1 were not wired in pairs, how many phases would this motor have?
25.5) If the coils in Figure 25.1 were not wired in pairs, how many stages would the electrical cycle contain?
25.6) Explain why a high-resolution encoder is necessary to achieve the smoothest torque output when using
sinusoidal drive.
25.7) Using the types of subsystems commonly available on a microcontroller, how would you generate (in
general terms) the varying drive currents necessary to implement sinusoidal drive?
25.8) If a microcontroller with circuitry to measure coil currents were used to implement sensor-less
commutation, explain one way that you could use the microcontroller to measure the inductance of the
coils.
25.9) Cite three reasons for why a brushless DC motor would be a superior choice over a brushed motor in a
laptop computer cooling application.
25.10) What is the alternative to block commutation for a brushless DC motor? Why would a designer choose
block commutation?
25.11) How many output transistors are necessary in the drive circuit for delta wound motor? Is there an
alternative winding and/or wiring layout that requires fewer transistors?