Compound overvoltage protection device and application thereof in semiconductor convertor equipment

Abstract

The invention relates to an overvoltage protection device and an application thereof. ZnO-Bi2O3-TiO2 high-energy zinc oxide varistors and ZnO-Bi2O3-Sb2O3 high-voltage zinc oxide varistors are combined in different modes to form two overvoltage protection devices. One is electrically connected with an alternating current lead-in side of semiconductor convertor equipment, and the other is electrically connected with a direct current side or a convertor output side of the semiconductor convertor equipment. When lightning overvoltage happens, the performance advantages of the ZnO-Bi2O3-Sb2O3 high-voltage zinc oxide varistors can be fully exerted. When switching overvoltage happens, the performance advantages of the ZnO-Bi2O3-TiO2 high-energy zinc oxide varistors are fully exerted. Therefore, the functions of effectively inhibiting the switching overvoltage and the lightning overvoltage are realized. The overvoltage protection device is simple in structure and easy in realization.

Description

technical field [0001] The invention relates to an overvoltage protector, in particular to an overvoltage protector applied in semiconductor converter equipment. Background technique [0002] Semiconductor converter equipment is electrical equipment that converts the voltage, current, frequency, waveform, phase number and other power or characteristics of the power system, including rectifiers (AC to DC), inverters (DC to AC), choppers , AC voltage regulator, frequency converter and DC-DC converter, etc. At present, semiconductor converter equipment has been widely used in metallurgy, chemical industry, electric power, mining machinery, transportation and other fields. The core functional components of semiconductor converter equipment are various power semiconductor devices produced using silicon semiconductor technology, including rectifier diodes, thyristors and their derivatives, power transistors and their derivatives, and high-efficiency power optoelectronic devices. ...

AI Technical Summary

Problems solved by technology

[0013] In addition, a single-phase-to-earth fault occurs on the AC input side and figure 1 Improper selection of capacitors in the medium C protection measures can also cause lightning strike accidents, so I won’t go into details here.

In short, the lightning faults of semiconductor converter equipment are all caused by poor insulation between a certain phase line on the secondary side of the power supply transformer or a conductor or component connected to the phase line and the ground. In actual operation, the equipment's Insulation to ground cannot be guaranteed to be foolproof. Therefore, in order to ensure long-term safe operation of semiconductor converter equipment, in addition to protection against operating overvoltage, effective protection measures against lightning overvoltage must also be taken.

[0014] Although figure 1 The protective measures A and B in the middle have a certain inhibitory effect on the lightning overvoltage, but from the actual use effect, the ability of these two protective measures to inhibit the lightning overvoltage is obviously not enough

[0015] In various overvoltage protection fields, zinc oxide varistors are the most cost-effective and widely used components, among which ZnO-Bi 2 o 3 -TiO 2 It is a high-energy zinc oxide varistor and its improved products (Chinese patent 200910049087.0) have been widely used in the operation overvoltage protection of semiconductor converter equipment (Chinese patent ZL200720037734.2, Chinese patent ZL200720037736.1, Chinese patent ZL200420054800.3), but according to the relevant usage specifications, high-energy zinc oxide varistors are used for differential mode protection, that is, they are connected between the phase lines on the AC input side of the converter equipment or at both ends of the output side, so -Lightning overvoltage between ground and output cable-ground has no suppression capability

In addition, the advantage of the high-energy zinc oxide varistor sheet is that it has a large energy capacity (350-750J / cm 3 ), strong ability to withstand long pulse width impulse current, but the limiting voltage ratio under high current is high (current density 30A / cm 2 The limiting voltage ratio is 1.80~2.25, and the current density is 2kA / cm 2 The lower limit voltage ratio is 3.8~5.0), and the ability to withstand short pulse width impulse current is poor, so the high-energy zinc oxide varistor is only suitable for operating overvoltage with small discharge current, long discharge time, and large surge energy. It is not suitable for lightning overvoltage protection with large discharge current, short discharge time, and small surge energy; even if common mode protection is used, the high-energy zinc oxide varistor is connected between phase and ground Between the output cable and the ground, the lightning overvoltage cannot be effectively suppressed, and it will also accelerate the aging of the high-energy zinc oxide varistor

[0016] The high-energy zinc oxide varistor described in Chinese patent 200910049087.0 is a product modified by using nanomaterials and nanotechnology to modify the traditional high-energy zinc oxide varistor. Although its performance has been greatly improved, but The limiting voltage ratio under high current and the stability under short pulse still cannot meet the requirements of lightning overvoltage protection

However, the action (conduction) of these two kinds of pressure-sensitive elements is triggered by the external voltage, and they have no ability to judge the type of overvoltage and distinguish the action.

Therefore, the technology of combining these two different types of varistors into one product has not been reported so far.

Images