Performance of a Brushless DC (BLDC) motor using a three-phase inverter

1. What is the primary advantage of a BLDC motor over a brushed DC motor?

a) Lower cost of brushes
b) Electronic commutation eliminates brush wear
c) Uses AC supply directly
d) Simpler construction

2. In a three‐phase inverter for a BLDC motor, how many switching devices are used?

a) 3
b) 4
c) 6
d) 8

3. What is the phase shift between the three output voltages of the inverter?

a) 90°
b) 120°
c) 180°
d) 60°

4. Which switching pattern energizes only two phases at a time?

a) Sinusoidal PWM
b) Field‐oriented control
c) Six‐step commutation
d) Space‐vector PWM

5. In six‐step commutation, what happens during each state?

a) All three phases are energized
b) Only one phase is energized
c) Two phases are energized, one is off
d) No phase is energized