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3. Electromagnetic sources of permanent excitation
Generally speaking, and due to the constant progress of power electronics, the control part of electrical machines must be taken into account when analyzing the mechanical excitation they produce.
3.1 Alternator case
During network disturbances, variations in electromagnetic torque occur. This torque is the sum of :
a constant torque ;
a damped, virtually sinusoidal periodic torque, corresponding to the oscillations of the unit after the fault has been eliminated, with a frequency of the order of 0.3 to 1.5 Hz ;
a torque with a frequency of 50 Hz, due to the presence of a DC component in the stator current, which is damped with a time constant...
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Electromagnetic sources of permanent excitation