Introduction: Key devices in power electronics

Silicon-controlled rectifiers (SCRs), also known as thyristors, are semiconductor power devices with a four-layer three-way junction framework (PNPN). Given that its introduction in the 1950s, SCRs have actually been commonly made use of in commercial automation, power systems, home device control and various other areas as a result of their high hold up against voltage, big existing lugging capacity, fast reaction and simple control. With the growth of innovation, SCRs have actually developed into numerous kinds, including unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions between these types are not only mirrored in the structure and functioning concept, yet likewise establish their applicability in different application scenarios. This article will certainly begin with a technical viewpoint, combined with particular criteria, to deeply analyze the primary distinctions and regular uses of these four SCRs.

Unidirectional SCR: Standard and steady application core

Unidirectional SCR is one of the most fundamental and typical sort of thyristor. Its framework is a four-layer three-junction PNPN plan, including three electrodes: anode (A), cathode (K) and gateway (G). It just allows current to stream in one instructions (from anode to cathode) and switches on after the gate is activated. As soon as activated, also if the gate signal is eliminated, as long as the anode current is above the holding existing (normally much less than 100mA), the SCR remains on.

(Thyristor Rectifier)

Unidirectional SCR has strong voltage and current tolerance, with an onward repeated top voltage (V DRM) of up to 6500V and a rated on-state ordinary present (ITAV) of up to 5000A. For that reason, it is extensively used in DC electric motor control, commercial furnace, uninterruptible power supply (UPS) correction components, power conditioning tools and other events that call for continual transmission and high power handling. Its advantages are basic structure, inexpensive and high reliability, and it is a core component of lots of typical power control systems.

Bidirectional SCR (TRIAC): Suitable for air conditioner control

Unlike unidirectional SCR, bidirectional SCR, also known as TRIAC, can accomplish bidirectional transmission in both favorable and unfavorable half cycles. This framework consists of 2 anti-parallel SCRs, which permit TRIAC to be triggered and turned on any time in the air conditioning cycle without changing the circuit connection approach. The balanced transmission voltage variety of TRIAC is generally ± 400 ~ 800V, the maximum load current is about 100A, and the trigger current is much less than 50mA.

Due to the bidirectional conduction attributes of TRIAC, it is especially ideal for a/c dimming and rate control in family devices and customer electronic devices. For example, devices such as light dimmers, follower controllers, and ac system fan rate regulatory authorities all depend on TRIAC to attain smooth power policy. Furthermore, TRIAC also has a reduced driving power need and appropriates for integrated design, so it has actually been commonly utilized in smart home systems and small devices. Although the power density and changing rate of TRIAC are not comparable to those of new power gadgets, its inexpensive and convenient usage make it a vital player in the field of little and medium power air conditioner control.

Gateway Turn-Off Thyristor (GTO): A high-performance agent of active control

Entrance Turn-Off Thyristor (GTO) is a high-performance power gadget created on the basis of traditional SCR. Unlike average SCR, which can only be turned off passively, GTO can be switched off proactively by using an unfavorable pulse current to eviction, hence accomplishing even more versatile control. This attribute makes GTO carry out well in systems that need constant start-stop or quick action.

(Thyristor Rectifier)

The technical parameters of GTO show that it has incredibly high power managing ability: the turn-off gain has to do with 4 ~ 5, the maximum operating voltage can get to 6000V, and the optimum operating current is up to 6000A. The turn-on time is about 1μs, and the turn-off time is 2 ~ 5μs. These performance indicators make GTO extensively made use of in high-power scenarios 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 reasonably complicated and has high switching losses, its performance under high power and high vibrant action needs is still irreplaceable.

Light-controlled thyristor (LTT): A dependable choice in the high-voltage seclusion environment

Light-controlled thyristor (LTT) uses optical signals as opposed to electrical signals to activate transmission, which is its greatest attribute that identifies it from various other sorts of SCRs. The optical trigger wavelength of LTT is generally in between 850nm and 950nm, the feedback time is gauged in nanoseconds, and the insulation level can be as high as 100kV or over. This optoelectronic seclusion mechanism considerably improves the system’s anti-electromagnetic interference capability and safety and security.

LTT is primarily utilized in ultra-high voltage direct existing transmission (UHVDC), power system relay security tools, electro-magnetic compatibility protection in clinical equipment, and armed forces radar interaction systems etc, which have very high demands for safety and security. For example, many converter stations in China’s “West-to-East Power Transmission” job have actually taken on LTT-based converter valve components to make sure secure operation under exceptionally high voltage problems. Some progressed LTTs can additionally be combined with gate control to accomplish bidirectional transmission or turn-off functions, additionally broadening their application variety and making them an excellent choice for fixing high-voltage and high-current control problems.

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Luoyang Datang Energy Tech Co.Ltd focuses on the research, development, and application of power electronics technology and is devoted to supplying customers with high-quality transformers, thyristors, and other power products. Our company mainly has solar inverters, transformers, voltage regulators, distribution cabinets, thyristors, module, diodes, heatsinks, and other electronic devices or semiconductors. If you want to know more about , please feel free to contact us.(sales@pddn.com)

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