## 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 |