Protection-of-diodes-thyristors二极管及晶闸管保护电路介绍.doc

Protection of diodes & thyristors二极管＆晶闸管的保护
Index目录
Voltage surge protection电压浪涌保护 1
Uncontrolled rectifier circuits不可控整流电路 1
Controllable switches (thyristors)可控硅开关（晶闸管） 2
Circuits 电路 2
Overvoltage protection using varistors 通过压敏电阻进行过电压保护 4
Snubber circuits based on siIicon avalanche diodes 基于雪崩二极管的缓冲电路 4
Overcurrent protection 过电流保护 5
Bimetall thermostats 双金属自动调温器 5
Temperature-dependent resistors 温度传感电阻 5
Fuses 保险丝 5

Voltage surge protection电压浪涌保护

The use of RC networks turns the inductors in the circuit to series resonant circuits, converting the steeply increasing voltage peaks into attenuated oscillations of low amplitude.
RC缓冲电路的使用将利用串联谐振电路的电感，把急剧增加的电压峰值转换成低振幅的衰减振荡值。

Uncontrolled rectifier circuits不可控整流电路

In uncontrolled bridge circuits, it is normally sufficient to include a snubber on the DC side only. It is often not needed to include any protection circuit as long as the maximum breaking voltage of the diodes is significantly higher than the operation voltage.
在不可控桥式整流电路中，通常仅在直流侧有一个缓冲电路便足够，它往往不需要包括任何保护电路，只要保证二极管的最大截止电压高于实际电路电压即可。

Controllable switches (thyristors)可控硅开关（晶闸管）

Thyristors have to be protected not only from excessive non-permissible surges, but also - and more importantly - from the steep rate of rise.
晶闸管的保护不仅要考虑过大的浪涌，而且更重要的是要考虑陡峭的上升沿。

The use of a single-thyristor snubber is, however, limited because the capacitors discharge through these networks during triggering and thus cause undesired stress with a steep current rate of rise (di/dt stress).
然而，使用一个单晶闸管缓冲器有限的，因为在触发过程中通过这些电路的电容放电，会导致一个陡峭的上升率（di / dt）产生。

In thyristor assemblies for low current densities and high voltages where relatively small capacitance and high-ohmic resistances are sufficient, this di/dt stress is still relatively low, meaning that here a single-switch snubber alone is often enough.
在晶闸管组件中，对于低电流密度和高电压的要求，相对较小的电容值和高阻抗值是足够的，di / dt的压力仍然比较低，也就是说，这里的单开关缓冲往往也是足够了。

For higher current densities, however, the solution is to use an AC side snubber.
然而，对于高电流密度，一般都是利用交流侧缓冲电路来解决。
For very high power, in particular for parallel thyristor circuits, it can be of advantage to connect the RC circuit via an auxiliary bridge.
对于非常高的功率场合，特别是对于晶闸管并联的电路，通过一个附加桥式电路连接的缓冲电路会有比较大的优势。

Circuits 电路

· Dimensioning guidelines for single-switch snubbers 对于单开关缓冲电路的尺寸规格 说明

Assumption: around half of the energy represented by the recovered charge Qrr is transferred to the circuit in the form of an overvoltage.
假设：大约一半的能量被恢复充电电荷通过过电压的形式转移至电路中。

The table below features typical RC values for SEMIPACK modules:
下表中给出了SEMIPACK模块的RC缓冲电路的典型参数。

· Snubbers for AC voltage converters (W1C) 交流电压转换器的缓冲电路（W1C）

W1C circuits comprise two antiparallel thyristors; the following, however, applies to a circuit comprising one thyristor with antiparallel diode. This is always equipped with a snubber circuit, in the simplest case comprising one common RC element (Figure 4.4.10). If each of the antiparallel components has its own fuse protection, then each must also be equipped with its own RC element.

W1C电路包括两个反并联晶闸管；下图中，适用于包括一个反并二极管、晶闸管的电路。这往往就是一个缓冲电路，最简单的情况就是配置一个常用的RC元件（图4.4.10）。如果反并联组件的每个器件都有对应的保险丝保护，那么每个器件都必须也要配置对应的RC元件。

The values for capacitor C (μF) and resistor R (Ω) can be determined using the following formulae:
根据以下公式可以计算RC电路中的R和C的参考值。

Overvoltage protection using varistors 通过压敏电阻进行过电压保护

The resistance of a varistor decreases as the voltage increases. Varistors can be used to attenuate overvoltage on the AC or on the DC side, or even as single-switch snubbers
One shortcoming of varistors is that they do not attenuate the voltage dv/dt. Thus, in thyristors with low dv/dt values, an additional RC snubber is needed.
压敏电阻的电阻随着电压升高会降低，可以用来衰减交流或直流侧的过电压或者用于单开关的缓冲器中。
压敏电阻的缺点之一是，他们不能衰减电压的变化率。因此，对于较低的dv/ dt值的晶闸管，额外的RC缓冲电路是必要的。

Snubber circuits based on siIicon avalanche diodes 基于雪崩二极管的缓冲电路

Also known as clamping diodes (transient voltage suppressors), they have the advantage over RC snubbers of being small in size and having lower energy consumption.

该雪崩二极管又称钳位二极管（瞬态电压抑制器），他们有体积小和能耗更低的RC缓冲器的优势。

Overcurrent protection 过电流保护

Bimetall thermostats 双金属自动调温器
Bimetal thermostats contain bimetal discs which, at a certain factory-set temperature, snap from one position to the next, opening or closing a contact in the process.
双金属温控器包含双金属碟片，在一种出厂设置的温度下，通过打开过关闭接触点实现从一种状态到另外一种状态的转换。

Temperature-dependent resistors 温度传感电阻
Temperature-dependent resistors have the advantage over bimetal thermostats that they respond to temperature changes more quickly. An additional electronic circuit is needed to convert the change in resistance into a signal that can, for example, trigger a protective device.
温度传感电阻拥有比双金属温控器更迅速地响应温度变化的优势。需要一个额外的电子电路将电阻的变化转换成一个信号来触发保护装置。

Fuses 保险丝
In bridge circuits, two power semiconductors each have a common AC terminal. For this reason they can be protected by a common fuse in the AC supply line. This is known as a phase or AC side fuse.
在整流桥电路中，两个功率半导体有一个共同的交流终端。因此，他们可以通过在交流供电端增加普通的保险丝进行保护。这就是所谓的单相或交流侧保险丝。

If rectifier diodes or thyristors are connected in parallel for high power densities, each semiconductor component is equipped with a fuse. Short circuits shall only occur very seldom.
如果为了考虑高功率密度将整流二极管或晶闸管并联，每一个半导体元件需要配置一个保险丝，这样可以避免短路的发生。

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