Elevator Mechanic Practice Exam

Which kind of core material is used in the field windings of a DC motor to optimize its performance?

1. Laminated core for high permeability

2. Solid core for high conductivity

3. Iron core for high thermal resistance

4. Copper core for high durability

The correct answer is: Laminated core for high permeability

Using a laminated core for the field windings of a DC motor is an effective choice because it minimizes eddy current losses and optimizes magnetic performance. The laminations, which are thin layers of material insulated from each other, reduce the overall electrical conductivity within the core. This is important since eddy currents can generate heat and waste energy, diminishing the motor's efficiency and performance. A laminated core thus enhances the magnetic properties of the motor while maintaining optimal performance levels. The other options, while they present some aspects of core materials, do not specifically cater to the performance optimization for DC motors. Solid cores do not provide the same benefits in terms of eddy current reduction as laminations do. An iron core's thermal resistance is not a critical factor for improving magnetic performance, and a copper core emphasizes conductivity rather than magnetic properties, which is less favorable for field windings.