Introduction: Trick tools in power electronics
Silicon-controlled rectifiers (SCRs), also known as thyristors, are semiconductor power tools with a four-layer three-way joint framework (PNPN). Considering that its introduction in the 1950s, SCRs have been commonly used in industrial automation, power systems, home device control and various other areas as a result of their high withstand voltage, big existing bring capacity, rapid response and easy control. With the growth of technology, SCRs have developed right into many types, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The distinctions in between these kinds are not just shown in the structure and working principle, yet additionally identify their applicability in various application situations. This post will start from a technical viewpoint, combined with specific specifications, to deeply examine the primary differences and common uses of these four SCRs.
Unidirectional SCR: Standard and steady application core
Unidirectional SCR is the most fundamental and typical sort of thyristor. Its structure is a four-layer three-junction PNPN arrangement, including three electrodes: anode (A), cathode (K) and entrance (G). It just permits present to stream in one direction (from anode to cathode) and turns on after the gate is triggered. Once switched on, also if eviction signal is removed, as long as the anode current is above the holding existing (generally less than 100mA), the SCR stays on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and existing resistance, with a forward recurring optimal voltage (V DRM) of as much as 6500V and a ranked on-state ordinary existing (ITAV) of up to 5000A. Consequently, it is extensively made use of in DC electric motor control, industrial furnace, uninterruptible power supply (UPS) rectification parts, power conditioning gadgets and various other events that require continuous conduction and high power processing. Its advantages are basic structure, inexpensive and high dependability, and it is a core component of several standard power control systems.
Bidirectional SCR (TRIAC): Perfect for air conditioner control
Unlike unidirectional SCR, bidirectional SCR, likewise known as TRIAC, can attain bidirectional transmission in both positive and negative fifty percent cycles. This structure includes two anti-parallel SCRs, which allow TRIAC to be caused and switched on at any time in the AC cycle without altering the circuit link approach. The in proportion conduction voltage variety of TRIAC is typically ± 400 ~ 800V, the optimum load current is about 100A, and the trigger current is less than 50mA.
Due to the bidirectional conduction characteristics of TRIAC, it is particularly appropriate for AC dimming and rate control in house devices and consumer electronic devices. For example, tools such as light dimmers, follower controllers, and air conditioner follower rate regulators all count on TRIAC to attain smooth power law. Furthermore, TRIAC likewise has a lower driving power need and is suitable for incorporated layout, so it has been commonly made use of in clever home systems and tiny home appliances. Although the power density and changing speed of TRIAC are not comparable to those of brand-new power devices, its low cost and convenient use make it a vital player in the area of small and medium power air conditioner control.
Gateway Turn-Off Thyristor (GTO): A high-performance agent of active control
Gate Turn-Off Thyristor (GTO) is a high-performance power device created on the basis of typical SCR. Unlike normal SCR, which can only be shut off passively, GTO can be turned off actively by using an adverse pulse current to the gate, therefore attaining more versatile control. This function makes GTO do well in systems that call for regular start-stop or fast action.
(Thyristor Rectifier)
The technical criteria of GTO show that it has very high power dealing with ability: the turn-off gain has to do with 4 ~ 5, the maximum operating voltage can get to 6000V, and the maximum operating current is up to 6000A. The turn-on time has to do with 1μs, and the turn-off time is 2 ~ 5μs. These performance indicators make GTO commonly made use of in high-power situations such as electric locomotive grip systems, big inverters, commercial electric motor frequency conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is relatively complex and has high changing losses, its efficiency under high power and high vibrant action requirements is still irreplaceable.
Light-controlled thyristor (LTT): A trusted option in the high-voltage seclusion atmosphere
Light-controlled thyristor (LTT) utilizes optical signals rather than electric signals to set off transmission, which is its biggest attribute that distinguishes it from various other sorts of SCRs. The optical trigger wavelength of LTT is typically between 850nm and 950nm, the action time is measured in milliseconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion mechanism greatly improves the system’s anti-electromagnetic interference ability and safety.
LTT is generally used in ultra-high voltage straight present transmission (UHVDC), power system relay defense gadgets, electro-magnetic compatibility defense in medical tools, and army radar interaction systems etc, which have incredibly high requirements for security and security. For instance, lots of converter terminals in China’s “West-to-East Power Transmission” project have actually taken on LTT-based converter valve modules to make certain stable operation under very high voltage problems. Some progressed LTTs can additionally be incorporated with gateway control to achieve bidirectional conduction or turn-off functions, even more broadening their application variety and making them a perfect choice for solving high-voltage and high-current control problems.
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