In a synchronous motor, as the DC amperage increases, what happens to the AC amperage?

In a synchronous motor, as the DC amperage increases, the AC amperage actually decreases. This behavior can be understood through the motor's operation principles, specifically the relationship between the excitation current and the stator current.

When the DC amperage supplied to the rotor increases, it enhances the magnetic field strength of the rotor. This stronger magnetic field can lead to more efficient operation of the motor, as it creates a better magnetic interaction with the stator's rotating magnetic field. Consequently, the synchronous motor becomes more effective at converting electrical energy into mechanical energy.

As the rotor's magnetic field strength increases, the motor requires less AC amperage to maintain the same output power. This is because the increased excitation helps the motor operate closer to its synchronous speed, allowing the machine to draw less current from the AC supply to maintain the desired torque.

This principle is critical in the understanding of synchronous motors as it illustrates the balance between excitation and current requirements, showcasing how changes in one can significantly impact the performance and current draw of the other.