DC motors have been used in the past for various applications, but nowadays induction motors have become more popular and are widely used. There are several reasons for this shift in preference:

Cost Efficiency:
- Using DC motors increases the initial cost of the system. DC motors require additional components such as brushes and a commutator, which increase the overall cost of the motor.
- On the other hand, induction motors do not require these additional components, making them more cost-effective.

Efficiency and Performance:
- Induction motors offer higher efficiency compared to DC motors. They can convert electrical energy into mechanical energy more effectively, resulting in less energy loss.
- Induction motors also provide better performance in terms of speed control. With DC motors, obtaining variable constant speed can be challenging and less efficient. In contrast, induction motors can achieve variable constant speed more efficiently.

Maintenance and Durability:
- DC motors are prone to wear and tear due to the presence of brushes and commutators. These components require regular maintenance and replacement, increasing the overall maintenance cost of the system.
- Induction motors, on the other hand, do not have brushes and commutators, making them more durable and requiring less maintenance.

Applications:
- Induction motors are suitable for a wide range of applications, including industrial machinery, household appliances, and automotive systems.
- Their versatility and efficiency make them a preferred choice in various industries.

Environmental Impact:
- Induction motors are considered more environmentally friendly compared to DC motors. They have a higher energy efficiency rating, which means they consume less electricity and reduce overall energy consumption.

In conclusion, the shift from DC motors to induction motors is driven by factors such as cost efficiency, performance, maintenance requirements, versatility, and environmental impact. Induction motors offer advantages in terms of cost, efficiency, speed control, durability, and environmental sustainability, making them a preferred choice in modern applications.