DocID18343 Rev 3

9/22

AN3327

Universal motor concepts

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Figure 4. A partially loaded motor note the phase shift of the BEMF

In a partially loaded motor, the back EMF has shifted to increase the percentage of driving

torque over the braking torque. This shift continues as external loading is increased until the

loading exceeds the potential torque capability. At that point the synchronization between

electrical rotation and mechanical rotation ceases and the motor stalls.

Figure 5. A fully loaded motor

1.

Note the complete alignment of current and BEMF.

In a fully loaded motor the moment that the torque demand causes the back EMF to shift

any further, the output torque decreases. Then the motor stops rotating.