Master Electrician Practice Exam

For a motor that provides continuous-duty operation, which design type is considered standard?

1. Design A

2. Design B

3. Design C

4. Design D

The correct answer is: Design B

In the context of electric motors, the standard design type for continuous-duty operation is designated as Design B. This type of motor is characterized by its ability to operate efficiently under continuous load conditions while maintaining a normal temperature rise and protecting against overheating. Design B motors are built to handle moderate starting torque and feature a good balance of efficiency and performance, making them suitable for a wide range of applications such as fans, pumps, and compressors that require sustained operation over extended periods. This differentiation from other design types is essential for practical applications. Design A, for instance, is geared more for lower starting torque, while Design C typically provides high starting torque for applications that demand significant initial push. Design D, on the other hand, is focused on very high starting torque and is often employed in specific heavy-duty applications. Thus, Design B stands out as the most suitable and commonly adopted choice for continuous-duty operation.