Analysis of types and applications of silicon controlled rectifiers (SCRs): unidirectional, bidirectional, turn-off and light-controlled types
Intro: Secret tools in power electronic devices
Silicon-controlled rectifiers (SCRs), also referred to as thyristors, are semiconductor power gadgets with a four-layer triple joint framework (PNPN). Given that its introduction in the 1950s, SCRs have actually been extensively utilized in commercial automation, power systems, home appliance control and various other areas as a result of their high endure voltage, large present carrying ability, fast action and simple control. With the growth of technology, SCRs have developed right into numerous types, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions between these kinds are not just reflected in the framework and working concept, yet likewise determine their applicability in different application scenarios. This post will certainly begin with a technical viewpoint, incorporated with details specifications, to deeply examine the major distinctions and common uses these four SCRs.
Unidirectional SCR: Fundamental and secure application core
Unidirectional SCR is one of the most fundamental and common kind of thyristor. Its structure is a four-layer three-junction PNPN arrangement, consisting of 3 electrodes: anode (A), cathode (K) and gate (G). It just allows present to stream in one direction (from anode to cathode) and activates after eviction is triggered. When activated, even if eviction signal is removed, as long as the anode current is greater than the holding present (normally less than 100mA), the SCR continues to be on.
(Thyristor Rectifier)
Unidirectional SCR has solid voltage and current tolerance, with an onward repetitive optimal voltage (V DRM) of as much as 6500V and a ranked on-state typical present (ITAV) of approximately 5000A. Therefore, it is extensively used in DC motor control, commercial heater, uninterruptible power supply (UPS) correction parts, power conditioning devices and other events that require continual conduction and high power processing. Its advantages are simple structure, inexpensive and high reliability, and it is a core element of several typical power control systems.
Bidirectional SCR (TRIAC): Perfect for air conditioner control
Unlike unidirectional SCR, bidirectional SCR, additionally referred to as TRIAC, can achieve bidirectional transmission in both positive and adverse fifty percent cycles. This framework includes two anti-parallel SCRs, which permit TRIAC to be activated and turned on at any moment in the AC cycle without altering the circuit connection method. The balanced transmission voltage series of TRIAC is usually ± 400 ~ 800V, the maximum tons current is about 100A, and the trigger current is less than 50mA.
Due to the bidirectional conduction characteristics of TRIAC, it is specifically suitable for a/c dimming and rate control in home appliances and consumer electronic devices. As an example, tools such as lamp dimmers, fan controllers, and air conditioning unit fan speed regulators all depend on TRIAC to attain smooth power law. In addition, TRIAC also has a lower driving power demand and is suitable for incorporated layout, so it has been extensively used in smart home systems and small devices. Although the power thickness and changing rate of TRIAC are not as good as those of new power tools, its low cost and convenient usage make it a crucial player in the area of small and average power air conditioner control.
Entrance Turn-Off Thyristor (GTO): A high-performance agent of active control
Entrance Turn-Off Thyristor (GTO) is a high-performance power tool created on the basis of traditional SCR. Unlike average SCR, which can just be turned off passively, GTO can be turned off actively by using an unfavorable pulse present to the gate, hence accomplishing even more adaptable control. This attribute makes GTO execute well in systems that need constant start-stop or quick feedback.
(Thyristor Rectifier)
The technological specifications of GTO show that it has very high power managing ability: the turn-off gain has to do with 4 ~ 5, the optimum operating voltage can reach 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 indications make GTO widely 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 switching losses, its performance under high power and high vibrant reaction needs is still irreplaceable.
Light-controlled thyristor (LTT): A dependable choice in the high-voltage seclusion environment
Light-controlled thyristor (LTT) utilizes optical signals instead of electrical signals to cause transmission, which is its greatest attribute that identifies it from various other kinds of SCRs. The optical trigger wavelength of LTT is generally between 850nm and 950nm, the response time is gauged in milliseconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion mechanism significantly boosts the system’s anti-electromagnetic interference ability and safety.
LTT is generally made use of in ultra-high voltage direct current transmission (UHVDC), power system relay defense gadgets, electromagnetic compatibility protection in medical tools, and army radar interaction systems etc, which have incredibly high requirements for safety and security and security. For instance, lots of converter terminals in China’s “West-to-East Power Transmission” project have actually adopted LTT-based converter shutoff components to make certain steady operation under exceptionally high voltage problems. Some progressed LTTs can also be combined with gateway control to accomplish bidirectional transmission or turn-off functions, additionally expanding their application array and making them an excellent selection for resolving high-voltage and high-current control troubles.
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