Intro: Key gadgets in power electronic devices
Silicon-controlled rectifiers (SCRs), also known as thyristors, are semiconductor power devices with a four-layer triple junction structure (PNPN). Because its intro in the 1950s, SCRs have been widely used in industrial automation, power systems, home device control and other fields as a result of their high endure voltage, large present carrying capability, fast feedback and simple control. With the growth of modern technology, SCRs have actually evolved right into many kinds, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions in between these types are not just mirrored in the structure and functioning principle, however likewise identify their applicability in various application scenarios. This short article will start from a technological point of view, integrated with certain criteria, to deeply assess the main differences and common uses of these four SCRs.
Unidirectional SCR: Basic and secure application core
Unidirectional SCR is the most fundamental and common sort of thyristor. Its framework is a four-layer three-junction PNPN setup, including three electrodes: anode (A), cathode (K) and entrance (G). It only allows present to stream in one direction (from anode to cathode) and switches on after eviction is activated. Once turned on, even if the gate signal is eliminated, as long as the anode current is more than the holding current (normally less than 100mA), the SCR remains on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and existing tolerance, with a forward repeated optimal voltage (V DRM) of approximately 6500V and a ranked on-state average current (ITAV) of up to 5000A. As a result, it is commonly utilized in DC electric motor control, industrial heating systems, uninterruptible power supply (UPS) rectification components, power conditioning devices and other occasions that need continual conduction and high power handling. Its benefits are simple structure, affordable and high dependability, and it is a core part of several standard power control systems.
Bidirectional SCR (TRIAC): Suitable for AC control
Unlike unidirectional SCR, bidirectional SCR, also referred to as TRIAC, can achieve bidirectional transmission in both positive and adverse fifty percent cycles. This structure includes two anti-parallel SCRs, which permit TRIAC to be activated and activated any time in the a/c cycle without transforming the circuit connection technique. The symmetrical conduction voltage variety of TRIAC is generally ± 400 ~ 800V, the maximum tons current is about 100A, and the trigger current is less than 50mA.
As a result of the bidirectional conduction characteristics of TRIAC, it is particularly suitable for AC dimming and rate control in household devices and customer electronics. For instance, devices such as light dimmers, fan controllers, and a/c unit follower rate regulatory authorities all depend on TRIAC to achieve smooth power policy. Furthermore, TRIAC likewise has a lower driving power demand and appropriates for incorporated layout, so it has been widely used in smart home systems and tiny appliances. Although the power density and changing speed of TRIAC are not just as good as those of brand-new power devices, its inexpensive and practical use make it an essential gamer in the field of little and moderate power AC control.
Gate Turn-Off Thyristor (GTO): A high-performance representative of energetic control
Entrance Turn-Off Thyristor (GTO) is a high-performance power tool established on the basis of traditional SCR. Unlike regular SCR, which can only be turned off passively, GTO can be turned off actively by using an adverse pulse existing to the gate, therefore accomplishing even more flexible control. This attribute makes GTO do well in systems that require frequent start-stop or fast reaction.
(Thyristor Rectifier)
The technological parameters of GTO show that it has extremely high power dealing with capability: the turn-off gain is about 4 ~ 5, the optimum operating voltage can reach 6000V, and the optimum operating current depends on 6000A. The turn-on time is about 1μs, and the turn-off time is 2 ~ 5μs. These performance signs make GTO extensively used in high-power scenarios such as electrical locomotive traction systems, huge inverters, commercial motor regularity conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is reasonably intricate and has high switching losses, its performance under high power and high dynamic feedback needs is still irreplaceable.
Light-controlled thyristor (LTT): A trustworthy option in the high-voltage isolation environment
Light-controlled thyristor (LTT) makes use of optical signals instead of electric signals to trigger transmission, which is its biggest attribute that identifies it from various other kinds of SCRs. The optical trigger wavelength of LTT is generally in between 850nm and 950nm, the reaction time is measured in nanoseconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion mechanism significantly enhances the system’s anti-electromagnetic interference capability and safety and security.
LTT is mostly made use of in ultra-high voltage direct present transmission (UHVDC), power system relay security gadgets, electro-magnetic compatibility defense in medical devices, and military radar interaction systems etc, which have exceptionally high requirements for safety and security. For example, lots of converter stations in China’s “West-to-East Power Transmission” job have embraced LTT-based converter shutoff components to make certain stable operation under incredibly high voltage problems. Some progressed LTTs can also be incorporated with gate control to attain bidirectional conduction or turn-off features, even more increasing their application array and making them a suitable selection for solving high-voltage and high-current control troubles.
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