1. The Hall effect sensor is used as the rotor position sensor for the BLDC motor.
A. True
B. False
Answer: A
The Hall effect sensor is used as the rotor position sensor for the BLDC motor. It is used to measure the strength of the magnetic field.
2. In BLDC motor armature windings are placed on the stator side.
A. True
B. False
Answer: A
In BLDC motor armature windings are placed on the stator side. It is more economical and less maintenance is required. Permanent magnets are placed on the rotor side.
3. BLDC motor is analogous to ______________
A. Permanent magnet synchronous motor
B. DC motor
C. Rotating Transformer
D. Single-phase Induction motor
Answer: A
BLDC motor is analogous to Permanent magnet synchronous motor. In BLDC motor armature windings are placed on the stator side. It is more economical and less maintenance is required. Permanent magnets are placed on the rotor side.
4. The speed of a BLDC motor can be controlled by __________
A. Changing input DC voltage
B. Changing temperature
C. Changing wind direction
D. Cannot be controlled
Answer: A
The speed of a BLDC motor can be controlled by changing the input DC voltage or the current using PWM. It can be achievable by using a transistor and chopper.
5. What are the advantages of BLDC motors?
A. Low cost
B. Simplicity
C. Reliability
D. All of the above
Answer: A
The BLDC motor is used in low-power applications. They have many advantages like low cost, simplicity, reliability, good performance, and long life.
6. Due to low inertia, BLDC motors have __________
A. Faster acceleration
B. Slower acceleration
C. High-cost
D. Low cost
Answer: A
Due to low inertia, BLDC motors have faster acceleration. BLDC motors have less weight. They can run at high speed than a conventional DC motor.
7. Calculate the electrical angle for the 6 pole machine. (θm represents mechanical angle)
A. 4×θm
B. 5×θm
C. 2×θm
D. 3×θm
Answer: D
The electrical angle for 6 pole machine is 3×θm.
One electrical angle is equal to a 180° mechanical angle.
θe=(P÷2)×θm.
8. Which of the following are the types of BLDC motor?
A. Unipolar, Bipolar
B. Unipolar, PWM
C. Bipolar, PWM
D. Synchronous, Induction
Answer: A
Unipolar and Bipolar are the types of BLDC motor. They use the Hall effect rotor position sensor and optical rotor position sensor.
9. Calculate peak-peak voltage if Vmax=45 V and Vmin=45 V.
A. 60 V
B. 30 V
C. 50 V
D. 0 V
Answer: D
Peak-Peak voltage is equal to the difference between the maximum and minimum voltage. It is mathematically represented as
Vp-p=Vmax-Vmin=45-45=0 V.
It signifies the signal is a DC signal.
10. Calculate the value of the Crest factor if Vpeak=141 V and Vr.m.s=100 V for sinusoidal voltage.
A. 1.41
B. 2.38
C. 4.42
D. 5.58
Answer: A
The value of the crest factor is Vpeak÷Vr.m.s=141÷100=1.41. It signifies the peak value is 1.41 times the r.m.s value.
