The synchronising torque T_SY of an alternator connected to an infinite busbar is given by:

(Where E is the generated EMF, X_S is the synchronous reactance, α is the slot angle and N_S is the synchronous speed)

Synchronizing Torque of an Alternator

Synchronizing torque (T_sy) is the torque that acts on a synchronous machine (alternator or motor) when there is a small deviation in its rotor angle (δ) from the synchronously rotating magnetic field. This torque helps the rotor return to its steady-state position, maintaining synchronization with the infinite busbar.

The synchronizing torque of an alternator connected to an infinite busbar is given by:

\(T_{s y}=\frac{28.64 α E^{2}}{X_{s} N_{s}} \mathrm{Nm}\)

where, E =  Generated EMF

X_s = Synchronous reactance

α = Slot angle

N_s = Synchronous speed

This equation indicates that:

• Higher EMF (E) leads to a higher synchronizing torque, making synchronization stronger.
• Higher synchronous reactance (X_S) reduces synchronizing torque, making the system more sensitive to disturbances.
• Higher synchronous speed (N_S) reduces synchronizing torque, meaning larger machines (higher N_S) might have weaker synchronization per unit power.