When we are repairing the inverter, we often encounter the inverter that triggers the overvoltage protection, at this time, I often wonder, can the overvoltage protection measures be different because of the overvoltage?
(1) For the interrupting overvoltage of the phase-shifting transformer, the resistor-capacitance absorption network and zinc oxide arrester are used to form the overvoltage absorption loop, and good results have been obtained.
(2) For the overvoltage generated by the transformer with load closing, the switch with good cycle performance can be selected (the switch will have different cycles after long-term operation); Adopt good resistance and capacitance absorption loop or active suppressor technology scheme; Transformers with electrostatic shielding measures can also effectively suppress closing overvoltages. However, for high-power transformers, it is quite difficult to make an electrostatic shield.
(3) For the overvoltage caused by the commutation of the rectifier element, it should be noted that the reverse withstand voltage of the rectifier element should be sufficient, and appropriate measures should be taken for the absorption circuit and the freewheeling circuit. Otherwise, the rectifier equipment may be damaged by overvoltage.
(4) Since the overvoltage of the inverter during operation is basically generated when the transformer is opened and closed, it is necessary to start with the transformer and find a way to suppress the overvoltage. We can try the following methods to solve the problem:
(1) Increase the excitation inductance and grounding capacitance of the transformer, and increase the excitation inductance will reduce the no-load current, thereby increasing the cost of the transformer.
(2) Increase the grounding capacitance of the transformer: It is easy to analyze in principle, but in fact, due to the structure and material limitations of the transformer itself, it is impossible to make any kind of insulation method or a transformer with a high insulation level, so it is quite difficult to greatly increase the grounding capacitance C of the transformer.
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