Which of these options are correct for a DC electric machine with a large air gap?

A DC electric machine with a large air gap would typically have the following implications:

1. Increased Magnetizing Current: A large air gap requires a larger magnetizing current to establish the necessary flux across the gap. This is due to the air gap presenting a high reluctance (opposition) to the magnetic field.

2. Reduced Efficiency: The increased magnetizing current leads to higher no-load losses, reducing the overall efficiency of the machine.

3. Reduced Power Factor: With a larger air gap, the power factor of the machine tends to decrease because the magnetizing current, which is out of phase with the voltage, increases in proportion to the total current.

4. Increased Armature Reaction: A larger air gap can exacerbate the effects of armature reaction, which can distort the main magnetic field and affect the machine’s performance, especially under heavy load conditions.

5. Higher Operational Costs: Due to reduced efficiency and lower power factor, machines with larger air gaps may incur higher operational costs over time, including increased energy consumption and potential need for more robust power conditioning equipment.

6. Potential for Greater Physical Size: To compensate for the larger air gap, the machine might need to be physically larger to maintain output performance, which can increase material costs and space requirements.

7. Decreased Mechanical Tolerance to Shock: A larger air gap can reduce the mechanical robustness of a machine, making it more sensitive to external shocks or vibration, which might lead to premature