Why synchronous impedance is not a constant?

Synchronous impedance is not a constant because it varies with operating conditions such as load, frequency, and machine construction. It is defined as the ratio of the voltage to the current at synchronous speed, but this relationship changes depending on the reactance and resistance of the machine as well as the power factor of the load. Additionally, factors such as saturation of magnetic materials and temperature can also influence synchronous impedance, leading to variations in its value.