Introduction: Trick gadgets in power electronics
Silicon-controlled rectifiers (SCRs), also known as thyristors, are semiconductor power tools with a four-layer triple junction structure (PNPN). Because its intro in the 1950s, SCRs have actually been extensively made use of in industrial automation, power systems, home appliance control and various other fields due to their high hold up against voltage, huge present lugging capability, rapid response and basic control. With the development of modern technology, SCRs have evolved right into numerous types, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The differences between these types are not just mirrored in the framework and functioning concept, but also identify their applicability in different application circumstances. This post will certainly begin with a technical viewpoint, integrated with specific parameters, to deeply evaluate the primary distinctions and normal uses these four SCRs.
Unidirectional SCR: Basic and stable application core
Unidirectional SCR is one of the most fundamental and usual type of thyristor. Its structure is a four-layer three-junction PNPN plan, including three electrodes: anode (A), cathode (K) and gateway (G). It just allows present to stream in one direction (from anode to cathode) and activates after eviction is set off. Once turned on, also if the gate signal is removed, as long as the anode current is higher than the holding present (normally much less than 100mA), the SCR continues to be on.
(Thyristor Rectifier)
Unidirectional SCR has solid voltage and existing resistance, with an ahead recurring top voltage (V DRM) of up to 6500V and a ranked on-state ordinary existing (ITAV) of approximately 5000A. For that reason, it is widely made use of in DC motor control, commercial heater, uninterruptible power supply (UPS) correction parts, power conditioning gadgets and other occasions that call for continual conduction and high power handling. Its advantages are basic framework, low cost and high reliability, and it is a core element of several conventional power control systems.
Bidirectional SCR (TRIAC): Perfect for AC control
Unlike unidirectional SCR, bidirectional SCR, likewise referred to as TRIAC, can accomplish bidirectional transmission in both positive and unfavorable half cycles. This framework contains 2 anti-parallel SCRs, which enable TRIAC to be activated and switched on at any time in the air conditioner cycle without changing the circuit connection technique. The balanced conduction voltage range of TRIAC is generally ± 400 ~ 800V, the maximum tons current is about 100A, and the trigger current is less than 50mA.
Because of the bidirectional transmission attributes of TRIAC, it is especially suitable for air conditioner dimming and rate control in home devices and customer electronic devices. For instance, tools such as light dimmers, follower controllers, and ac unit follower speed regulators all depend on TRIAC to accomplish smooth power policy. On top of that, TRIAC likewise has a reduced driving power demand and is suitable for integrated layout, so it has actually been widely used in smart home systems and small appliances. Although the power density and switching rate of TRIAC are not like those of brand-new power devices, its low cost and convenient use make it an important player in the area of tiny and medium power AC control.
Gate Turn-Off Thyristor (GTO): A high-performance agent of active control
Gate Turn-Off Thyristor (GTO) is a high-performance power device established on the basis of conventional SCR. Unlike average SCR, which can only be shut off passively, GTO can be shut off actively by applying a negative pulse existing to eviction, therefore achieving more flexible control. This feature makes GTO perform well in systems that need frequent start-stop or rapid feedback.
(Thyristor Rectifier)
The technical parameters of GTO show that it has exceptionally high power taking care of ability: the turn-off gain has to do with 4 ~ 5, the maximum operating voltage can get to 6000V, and the optimum operating current depends on 6000A. The turn-on time has to do with 1μs, and the turn-off time is 2 ~ 5μs. These efficiency indicators make GTO commonly utilized in high-power circumstances such as electrical engine traction systems, huge inverters, industrial motor regularity conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is relatively intricate and has high changing losses, its performance under high power and high vibrant action demands is still irreplaceable.
Light-controlled thyristor (LTT): A reliable selection in the high-voltage isolation environment
Light-controlled thyristor (LTT) utilizes optical signals as opposed to electric signals to cause conduction, which is its largest attribute that distinguishes it from other kinds of SCRs. The optical trigger wavelength of LTT is usually in between 850nm and 950nm, the feedback time is determined in milliseconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion device significantly improves the system’s anti-electromagnetic disturbance capacity and security.
LTT is generally used in ultra-high voltage direct present transmission (UHVDC), power system relay security gadgets, electromagnetic compatibility security in clinical tools, and military radar communication systems etc, which have extremely high requirements for security and security. For instance, many converter stations in China’s “West-to-East Power Transmission” task have adopted LTT-based converter valve components to make sure steady operation under very high voltage problems. Some advanced LTTs can also be combined with gate control to achieve bidirectional transmission or turn-off functions, further broadening their application variety and making them an optimal option for solving high-voltage and high-current control problems.
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