The correct answer is: C. either a.c. or d.c. supply
Traction motors are used to power electric locomotives and other rail vehicles. They can be powered by either alternating current (AC) or direct current (DC) supplies.
AC traction motors are more common in Europe and Asia, while DC traction motors are more common in North America. AC traction motors have the advantage of being more efficient, but they are also more complex and expensive. DC traction motors are simpler and less expensive, but they are also less efficient.
The type of traction motor used depends on a number of factors, including the voltage of the power supply, the speed of the locomotive, and the weight of the train.
In recent years, there has been a trend towards using AC traction motors in North America. This is due to the increasing availability of high-voltage AC power supplies, as well as the development of more efficient AC traction motors.
DC traction motors are still used in some applications, such as subway trains and light rail vehicles. However, AC traction motors are becoming increasingly popular for all types of rail vehicles.
Here is a brief explanation of each option:
- Option A: Traction magnets are operated from a.c. supply. This is not always the case. Traction magnets can be operated from either AC or DC supplies.
- Option B: Traction magnets are operated from d.c. supply. This is not always the case. Traction magnets can be operated from either AC or DC supplies.
- Option C: Traction magnets are operated from either a.c. or d.c. supply. This is the correct answer. Traction magnets can be operated from either AC or DC supplies.
- Option D: None of the above. This is not the correct answer. Traction magnets can be operated from either AC or DC supplies.