By hvhipot 
Corresponding to three inductance parameters, under certain capacitance parameters and other conditions, three different resonance phenomena may occur: linear resonance, ferromagnetic resonance, and parametric resonance
Linear resonance:
A resonant circuit is composed of ironless inductive elements (such as the inductance of transmission lines, leakage inductance of transformers) or iron core inductive elements with excitation characteristics close to linearity (such as arc suppression coils with air gaps in the iron core). Composed of capacitive components in the system. Under the action of a sine power supply, linear resonance may occur when the natural frequency of the system is equal to or close to the power supply frequency.
Ferromagnetic resonance (nonlinear resonance):
A resonant circuit consists of inductive components with iron cores (such as no-load transformers, voltage transformers) and capacitive components of the system. Due to the saturation phenomenon of iron core inductance components, the inductance parameters of the circuit are nonlinear. When certain resonance conditions are met, ferromagnetic resonance occurs, which has many unique properties.
Parameter resonance:
Inductive components with periodic changes in inductance parameters (such as the periodic changes in synchronous reactance of salient pole generators at Xd-Xq) form a loop with capacitive components of the system (such as no-load long lines). When the parameters are matched, the periodic changes in inductance and the continuous transfer of energy to the resonant system can cause parameter resonance overvoltage.
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