Analysis of types and applications of silicon controlled rectifiers (SCRs): unidirectional, bidirectional, turn-off and light-controlled types
Introduction: Secret devices in power electronics
Silicon-controlled rectifiers (SCRs), likewise referred to as thyristors, are semiconductor power tools with a four-layer three-way junction structure (PNPN). Considering that its intro in the 1950s, SCRs have actually been extensively made use of in commercial automation, power systems, home device control and other fields because of their high withstand voltage, big current lugging capacity, rapid action and straightforward control. With the advancement of technology, SCRs have actually developed into many kinds, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions between these kinds are not just mirrored in the structure and working principle, however also determine their applicability in various application circumstances. This article will certainly start from a technological perspective, combined with certain criteria, to deeply evaluate the main differences and common uses these 4 SCRs.
Unidirectional SCR: Standard and stable application core
Unidirectional SCR is the most basic and typical kind of thyristor. Its structure is a four-layer three-junction PNPN plan, including 3 electrodes: anode (A), cathode (K) and gate (G). It just permits current to move in one direction (from anode to cathode) and turns on after eviction is caused. As soon as switched on, even if the gate signal is eliminated, as long as the anode current is more than the holding existing (usually much less than 100mA), the SCR stays on.
(Thyristor Rectifier)
Unidirectional SCR has solid voltage and present resistance, with an onward repetitive peak voltage (V DRM) of approximately 6500V and a ranked on-state average existing (ITAV) of up to 5000A. As a result, it is widely made use of in DC motor control, industrial heater, uninterruptible power supply (UPS) correction components, power conditioning devices and other occasions that call for continuous transmission and high power processing. Its benefits are simple structure, low cost and high dependability, and it is a core element of lots of standard power control systems.
Bidirectional SCR (TRIAC): Perfect for AC control
Unlike unidirectional SCR, bidirectional SCR, likewise called TRIAC, can achieve bidirectional conduction in both favorable and adverse half cycles. This structure consists of two anti-parallel SCRs, which permit TRIAC to be activated and activated at any time in the air conditioner cycle without altering the circuit link technique. The in proportion transmission voltage series of TRIAC is typically ± 400 ~ 800V, the optimum load current is about 100A, and the trigger current is much less than 50mA.
Because of the bidirectional transmission qualities of TRIAC, it is particularly appropriate for a/c dimming and speed control in household home appliances and consumer electronics. For instance, devices such as light dimmers, follower controllers, and ac unit follower speed regulatory authorities all rely on TRIAC to accomplish smooth power law. On top of that, TRIAC also has a lower driving power requirement and appropriates for incorporated design, so it has been extensively used in wise home systems and small home appliances. Although the power thickness and switching rate of TRIAC are not as good as those of brand-new power gadgets, its inexpensive and hassle-free usage make it an important player in the field of tiny and average power a/c 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 ordinary SCR, which can just be turned off passively, GTO can be turned off actively by applying an adverse pulse current to the gate, therefore accomplishing more versatile control. This attribute makes GTO perform well in systems that require constant start-stop or quick reaction.
(Thyristor Rectifier)
The technical specifications of GTO reveal that it has very high power dealing with capability: the turn-off gain is about 4 ~ 5, the maximum operating voltage can get to 6000V, and the maximum 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 commonly used in high-power circumstances such as electrical locomotive grip systems, big inverters, commercial electric motor regularity conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is fairly complicated and has high changing losses, its efficiency under high power and high dynamic action requirements is still irreplaceable.
Light-controlled thyristor (LTT): A trustworthy selection in the high-voltage isolation atmosphere
Light-controlled thyristor (LTT) makes use of optical signals instead of electrical signals to set off transmission, which is its most significant attribute that differentiates it from various other types of SCRs. The optical trigger wavelength of LTT is generally in between 850nm and 950nm, the feedback time is measured in split seconds, and the insulation level can be as high as 100kV or above. This optoelectronic seclusion system greatly enhances the system’s anti-electromagnetic disturbance capacity and safety.
LTT is mostly used in ultra-high voltage straight existing transmission (UHVDC), power system relay protection tools, electromagnetic compatibility security in medical devices, and military radar communication systems etc, which have very high needs for security and stability. For instance, lots of converter terminals in China’s “West-to-East Power Transmission” project have actually taken on LTT-based converter valve components to guarantee steady operation under extremely high voltage problems. Some progressed LTTs can likewise be incorporated with gate control to attain bidirectional conduction or turn-off functions, further expanding their application array and making them an ideal choice for resolving high-voltage and high-current control problems.
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Introduction: Secret devices in power electronics Silicon-controlled rectifiers (SCRs), likewise referred to as thyristors, are semiconductor power tools with a four-layer three-way junction structure (PNPN). Considering that its intro in the 1950s, SCRs have actually been extensively made use of in commercial automation, power systems, home device control and other fields because of their high…