Why the angle δ, rotor angle is famously called as the load angle in the equation of rotor dynamics?

The angle δ, typically referred to as the rotor angle or the load angle in the context of rotor dynamics of synchronous generators, is crucial in understanding the operation of power systems. This angle δ is defined as the angle between the rotor’s magnetic axis and the stator’s magnetic axis, essentially representing the position of the rotor in relation to the magnetic field in which it is operating.

The reason δ is famously called the load angle is primarily due to its direct correlation with the mechanical power output of a synchronous generator. In essence, the load angle is a measure of the electrical load the generator is capable of supplying to the system. As the electrical load, or demand, on the generator increases, more mechanical power is required to maintain its operation at a constant frequency (usually 50 or 60 Hz, depending on the region). This increase in mechanical power causes the rotor to fall behind the synchronous speed of the electrical field created by the stator, increasing the angle δ.

The relationship between the mechanical power output P of a synchronous generator and the load angle δ can be mathematically expressed as follows:

[P = frac{EV}{X} sin(delta)]

– (E) represents the internal generated voltage per phase of the generator.

– (V) is the terminal voltage per phase.

– (X) is the synchronous reactance per phase.

– (delta) is the load angle.

As the load on the generator changes, so does the angle δ, making it