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Dynamic stability of a synchronous motor

A synchronous motor is initially running at no load (Point O) when a mechanical load P_m is suddenly applied. The ensuing swing curves (δ versus time) are plotted showing the cases of stablity, marginal stability, and instabilty. The power-angle curve is also plotted; the intersection B with P_m defines the steady-state equilibrium at δ_o. Sliding Point A along the power axis adjusts the load. Sliding Point C along the power curve adjusts the maximum swing angle δ_m .For stable operation, the blue area BCD must be equal to the red area OAB.

© M.Riaz