The main characteristics of ferromagnetic resonance and elimination method of voltage transformer

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     Ferromagnetic resonance

     Main features

    1) For the ferroresonance circuit in power potential function, the same loop may be not only a stable working state. How stablecircuit transition process in which the working state to causeexternal shock condition.

    2) Nonlinear ferromagnetic properties of PT is the fundamental reason of ferromagnetic resonance, but ferromagnetic component saturation effect itself also limits the amplitude ofovervoltage. In addition return loss also make resonance overvoltage by damping and restrictions. When the circuit resistance is greater than a certain value, won't appear the ferroresonance overvoltage strong.

    3) Series resonant circuit, the necessary condition for the ferroresonance overvoltage is ω 0=1/L0C< ω. Therefore, the ferromagnetic resonance can occur in a large rang

Fluid Couplings

     4) Maintain the resonant oscillation and the compensation loop resistance loss of energy by the power frequency power supply.In order to make the power energy into other resonant frequency energy, its conversion process must be periodically and rhythmic,i.e.... 1/2 (1, 2, 3...) Resonant frequency.

      5) On PT damage of ferromagnetic resonance. Magneticresonance (frequency) in general should have the following three conditions.

      The magnetic voltage transformer (PT) nonlinear effect is the main cause of ferromagnetic resonance.

      The PT inductance capacitance within 100 times, namelymatching parameters in the resonance range.

There must be the excitation conditions, such as PT suddenlyclosing, single-phase grounding suddenly disappeared, the system's outside interference or system operation over-voltageetc.

     According to 240 times the current test frequency resonantnormal current, power frequency resonant current of the normalcurrent of 40 ~ 60 times, high frequency resonant current smaller.In the Xie Zhenzhong frequency resonance, most destructive, ifgood insulation PT, power frequency and high in general will notendanger the safety equipment, and the conditions of 6kV system.

     The elimination of measures

     According to the characteristics of the above analysis of Ferroresonance in distribution system, it is not difficult to find thesolve way. The usual solution is:

     1) PT a neutral point with damping resistor. This method has been widely used in production of stereotypes products, more manufacturers, satisfactory results are obtained in the practicalapplication.

       2) In the PT open delta side parallel fixed (or variable) variabledamping, for some not too high or distribution.