Thyristor module has been become a thyristor
module, most currently USES two-way thyristor module, it has small, relatively simple structure, strong function, and the advantages of light weight, but it also has the bad anti-jamming ability of overload and, when they control large inductance load disturbance of shortcomings, such as network and the interference to below shows you how to avoid the deficiency of silicon controlled rectifier module.
A, bidirectional thyristor is a three-terminal device sensitivity, but we are no longer according to their Yin and Yang are two very very, but called T1 and T2, G for control, its control in regardless of the applied voltage is positive or negative trigger pulse trigger pulse can make the pole control, shown in figure 1 under the condition of four types of bidirectional thyristor can be triggered conduction, but triggering sensitivity to each other is not the same, which can guarantee the bidirectional thyristor into conducting state minimum gate current IGT, there is a difference between them (
Trigger the highest sensitivity, (
Trigger the lowest sensitivity, in order to ensure that trigger at the same time try to limit the gate current, should choose (
2, thyristor module overload protection thyristor module benefits a lot, but it's overload ability is poor, short time overcurrent, overvoltage element damage, thus to guarantee the normal work of the components, to be conditional (
More than permitted under the applied voltage is turning voltage, otherwise the control will not work;
Silicon controlled state average currents from the security perspective generally according to the maximum current of 1.
5 ~ 2 times to take;
To ensure control extremely reliable trigger, added to the control of trigger current generally is greater than its value, in addition to this, also must adopt measures to protect, general collective protection measures is quick fuse series in the circuit, the rated current SCR current average of 1.
Around five times, its position in the access to the ac or dc side, when the ac rated current take bigger, more commonly used the former, over voltage protection often occur in the presence of the inductance of the circuit, or disrupt a surge voltage or the ac ac transient process of the overvoltage.
Because, overvoltage spike high, short duration, often be suppressed by the absorbing circuit of the resistance and capacitance.
Three, thyristor module control large inductance load interference from the power grid and the interference of avoid SCR module control large inductance load with interference power grid and the interference phenomenon, the reason is that when the thyristor module of inductive loads connected to the control of a circuit when opening or closing, the coil in the current path is cut off, the rate of change is great, so produce a high voltage in the inductance, the voltage by the power of internal resistance on the ends of the switch contact, then the induction voltage and discharge until required by the induced voltage is lower than the discharge voltage, will produce great pulse beam in this process.
These pulses superimposed on the power supply voltage, beam and the interference to the power supply line or in the form of radiation to the surrounding space, the pulse of high amplitude, a very wide frequency, thus has the perceptual load switch point is a strong noise.
To prevent or reduce the noise, the phase shift control of ac voltage regulator is general processing methods have a lc filter circuit, the resistance capacity of damping and bidirectional diode damping circuit and other circuit.
Lc filter circuit, as shown in figure 2 (
, made up of lc resonant circuit, the cut-off frequency low pass is f = 1/2 PI Ic, generally take tens of KHZ low frequency.
Is another way to prevent or reduce the noise by using on-off ratio control ac voltage regulation mode, its principle is to use the zero trigger circuit, the zero in the power supply voltage control bidirectional thyristor conduction and globe, namely the control Angle is zero, so get a complete sine wave on the load, but the downside is applicable to the time constant is bigger than on and off cycle system, such as a thermostat.
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