Introduction: Secret gadgets in power electronics
Silicon-controlled rectifiers (SCRs), additionally known as thyristors, are semiconductor power devices with a four-layer three-way joint structure (PNPN). Considering that its introduction in the 1950s, SCRs have actually been commonly used in commercial automation, power systems, home appliance control and other fields due to their high endure voltage, big existing carrying ability, rapid response and basic control. With the advancement of modern technology, SCRs have advanced right into numerous kinds, including unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The differences between these kinds are not just shown in the structure and working concept, yet also establish their applicability in various application circumstances. This post will certainly begin with a technological point of view, combined with certain parameters, to deeply analyze the main differences and normal uses these 4 SCRs.
Unidirectional SCR: Fundamental and steady application core
Unidirectional SCR is one of the most basic and usual kind of thyristor. Its framework is a four-layer three-junction PNPN setup, including three electrodes: anode (A), cathode (K) and gateway (G). It only allows existing to move in one direction (from anode to cathode) and switches on after eviction is caused. Once switched on, even if the gate signal is eliminated, as long as the anode current is higher than the holding existing (usually much less than 100mA), the SCR continues to be on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and current tolerance, with a forward repetitive top voltage (V DRM) of as much as 6500V and a rated on-state ordinary present (ITAV) of as much as 5000A. For that reason, it is widely made use of in DC electric motor control, industrial heater, uninterruptible power supply (UPS) correction components, power conditioning tools and other occasions that need continuous conduction and high power handling. Its advantages are easy framework, low cost and high dependability, and it is a core part of many standard power control systems.
Bidirectional SCR (TRIAC): Perfect for a/c control
Unlike unidirectional SCR, bidirectional SCR, likewise known as TRIAC, can achieve bidirectional transmission in both positive and adverse fifty percent cycles. This framework includes two anti-parallel SCRs, which permit TRIAC to be activated and switched on at any time in the air conditioning cycle without changing the circuit link approach. The in proportion transmission voltage variety of TRIAC is normally ± 400 ~ 800V, the optimum tons current has to do with 100A, and the trigger current is less than 50mA.
Due to the bidirectional conduction features of TRIAC, it is particularly ideal for air conditioning dimming and speed control in home appliances and customer electronics. For example, gadgets such as light dimmers, follower controllers, and ac system follower rate regulators all rely upon TRIAC to accomplish smooth power law. In addition, TRIAC also has a reduced driving power need and is suitable for integrated design, so it has been extensively made use of in wise home systems and little appliances. Although the power density and changing speed of TRIAC are not just as good as those of brand-new power devices, its low cost and practical use make it a vital player in the area of little and moderate power air conditioner control.
Gate Turn-Off Thyristor (GTO): A high-performance agent of active control
Gateway Turn-Off Thyristor (GTO) is a high-performance power device developed on the basis of typical SCR. Unlike normal SCR, which can only be switched off passively, GTO can be turned off actively by using an adverse pulse current to the gate, thus achieving even more adaptable control. This attribute makes GTO perform well in systems that need frequent start-stop or quick reaction.
(Thyristor Rectifier)
The technological parameters of GTO show that it has very high power managing capability: the turn-off gain has to do with 4 ~ 5, the maximum operating voltage can reach 6000V, and the maximum operating current depends on 6000A. The turn-on time is about 1μs, and the turn-off time is 2 ~ 5μs. These performance indicators make GTO widely used in high-power circumstances such as electric locomotive grip systems, large inverters, industrial electric motor frequency conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is fairly complex and has high switching losses, its performance under high power and high vibrant feedback demands is still irreplaceable.
Light-controlled thyristor (LTT): A reliable option in the high-voltage isolation environment
Light-controlled thyristor (LTT) makes use of optical signals rather than electrical signals to activate conduction, which is its biggest feature that identifies it from other types of SCRs. The optical trigger wavelength of LTT is typically between 850nm and 950nm, the reaction time is measured in milliseconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion mechanism substantially enhances the system’s anti-electromagnetic disturbance capacity and safety.
LTT is mostly used in ultra-high voltage direct existing transmission (UHVDC), power system relay protection tools, electro-magnetic compatibility protection in clinical equipment, and army radar interaction systems etc, which have extremely high demands for security and security. As an example, numerous converter terminals in China’s “West-to-East Power Transmission” job have embraced LTT-based converter shutoff modules to make sure stable procedure under exceptionally high voltage conditions. Some progressed LTTs can likewise be incorporated with gate control to attain bidirectional conduction or turn-off features, additionally broadening their application array and making them an ideal option for solving high-voltage and high-current control issues.
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