Question

Following statements are given for DC motors

(a) DC motors require less maintenance than AC motors

(b) DC motors cannot provide high starting torque

(c) DC motors are not suitable for very high-speed applications

(d) The methods of speed control of DC motors are simpler and less expensive than those of AC motors

Which of the following statements are correct?
1. (a) and (c)
2. (a) and (b)
3. (b) and (c)
4. (c) and (d)

Answer 1

Correct Answer - Option 4 : (c) and (d)

BASICS	AC MOTOR	DC MOTOR
Nature of the Input Current	Alternating Current is the main input power in the AC motor	Direct Current is the main input power in the DC motor
Supply Phase	Both single-phase and three-phase supply are used	Only single-phase supply is used
Number of terminals	There are 3 input terminals RYB	There are two input terminals: Positive and Negative
Carbon Brushes	Absent	Two carbon brushes
Applications	Suitable for large ad industrial applications	Used in small and domestic applications
Starting	Not Self starting. It requires some external starting equipments	DC motors are self-starting
Maintenance Cost	Less Expensive as compared to DC Motor	DC motor maintenance is more expensive