How will the length of the air gap in a DC electric machine affect pulsational loss in pole faces?

The length of the air gap in a DC electric machine significantly influences the pulsational losses in pole faces. To comprehend this effect, it’s essential to understand what pulsational losses are and then how the air gap length comes into play.

1. Pulsational Losses Explained:

Pulsational losses, often referred to as pulsation losses, are a subset of core losses or iron losses in electrical machines, including DC electric machines. These losses primarily occur due to the variation in magnetic flux linkage in the core material caused by the air gap flux’s interaction with the stator and rotor teeth. Pulsational losses manifest as additional heating in the pole faces and adjacent areas, impacting the machine’s efficiency and performance.

2. Impact of Air Gap Length on Pulsational Losses:

The length of the air gap in a DC electric machine has a direct impact on the machine’s magnetic circuit. A longer air gap results in a higher reluctance of the magnetic circuit, which requires a higher magnetomotive force (MMF) to maintain the same level of magnetic flux. In relation to pulsational losses:

– Increased Air Gap Length: A longer air gap tends to increase the magnetic flux pulsations because the magnetic circuit becomes less stiff, making it more susceptible to variations caused by armature reaction or changes in load conditions. This can lead to higher pulsational losses because the increased flux variation induces more eddy currents and hysteresis in the pole faces and surrounding