Introduction: Secret devices in power electronics
Silicon-controlled rectifiers (SCRs), also referred to as thyristors, are semiconductor power gadgets with a four-layer triple joint structure (PNPN). Given that its intro in the 1950s, SCRs have been commonly used in industrial automation, power systems, home device control and other fields because of their high hold up against voltage, big existing lugging capacity, rapid action and easy control. With the growth of technology, SCRs have actually evolved into lots of types, including unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions between these kinds are not only shown in the structure and functioning principle, but additionally identify their applicability in different application situations. This post will certainly start from a technical point of view, combined with specific parameters, to deeply analyze the primary differences and regular uses of these 4 SCRs.
Unidirectional SCR: Fundamental and steady application core
Unidirectional SCR is one of the most fundamental and common type of thyristor. Its framework is a four-layer three-junction PNPN arrangement, consisting of 3 electrodes: anode (A), cathode (K) and gate (G). It only enables existing to move in one instructions (from anode to cathode) and switches on after the gate is caused. Once switched on, also if the gate signal is removed, as long as the anode current is greater than the holding current (usually less than 100mA), the SCR continues to be on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and existing tolerance, with an ahead repetitive peak voltage (V DRM) of up to 6500V and a rated on-state ordinary existing (ITAV) of up to 5000A. Therefore, it is commonly used in DC electric motor control, industrial heating systems, uninterruptible power supply (UPS) correction components, power conditioning devices and other celebrations that call for constant transmission and high power handling. Its benefits are easy structure, affordable and high integrity, and it is a core element of several conventional power control systems.
Bidirectional SCR (TRIAC): Perfect for air conditioner control
Unlike unidirectional SCR, bidirectional SCR, likewise referred to as TRIAC, can accomplish bidirectional conduction in both positive and negative half cycles. This structure contains 2 anti-parallel SCRs, which enable TRIAC to be activated and turned on at any moment in the air conditioner cycle without changing the circuit link technique. The in proportion conduction voltage series of TRIAC is usually ± 400 ~ 800V, the maximum load current has to do with 100A, and the trigger current is much less than 50mA.
As a result of the bidirectional conduction features of TRIAC, it is specifically suitable for AC dimming and speed control in home appliances and customer electronic devices. For example, gadgets such as lamp dimmers, follower controllers, and a/c follower rate regulators all rely on TRIAC to accomplish smooth power regulation. Additionally, TRIAC additionally has a reduced driving power demand and appropriates for integrated design, so it has actually been widely made use of in smart home systems and tiny home appliances. Although the power thickness and changing speed of TRIAC are not just as good as those of new power gadgets, its affordable and hassle-free use make it an essential player in the field of tiny and moderate power AC control.
Gateway Turn-Off Thyristor (GTO): A high-performance rep of energetic control
Gate Turn-Off Thyristor (GTO) is a high-performance power device created on the basis of traditional SCR. Unlike regular SCR, which can only be turned off passively, GTO can be shut off actively by using an adverse pulse present to the gate, thus attaining even more versatile control. This attribute makes GTO perform well in systems that call for frequent start-stop or quick response.
(Thyristor Rectifier)
The technological criteria of GTO show that it has incredibly high power dealing with capacity: 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 has to do with 1μs, and the turn-off time is 2 ~ 5μs. These efficiency signs make GTO extensively utilized in high-power circumstances such as electric locomotive 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 response requirements is still irreplaceable.
Light-controlled thyristor (LTT): A dependable option in the high-voltage isolation setting
Light-controlled thyristor (LTT) makes use of optical signals rather than electrical signals to trigger conduction, which is its most significant feature that distinguishes it from various other sorts of SCRs. The optical trigger wavelength of LTT is usually between 850nm and 950nm, the feedback time is gauged in nanoseconds, and the insulation level can be as high as 100kV or above. This optoelectronic isolation mechanism substantially enhances the system’s anti-electromagnetic disturbance capability and safety and security.
LTT is mainly used in ultra-high voltage straight current transmission (UHVDC), power system relay security devices, electromagnetic compatibility protection in clinical equipment, and military radar interaction systems and so on, which have very high demands for security and security. For example, many converter terminals in China’s “West-to-East Power Transmission” project have embraced LTT-based converter shutoff components to make certain secure procedure under very high voltage problems. Some advanced LTTs can also be combined with gate control to accomplish bidirectional transmission or turn-off features, even more broadening their application array and making them a perfect selection for fixing high-voltage and high-current control troubles.
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