Introduction: Secret devices in power electronic devices
Silicon-controlled rectifiers (SCRs), additionally referred to as thyristors, are semiconductor power gadgets with a four-layer three-way joint framework (PNPN). Given that its intro in the 1950s, SCRs have been extensively made use of in commercial automation, power systems, home device control and other areas as a result of their high stand up to voltage, big present carrying ability, rapid response and simple control. With the advancement of modern technology, SCRs have developed into numerous kinds, including unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The differences between these types are not only shown in the structure and working principle, but also establish their applicability in various application scenarios. This short article will begin with a technical perspective, integrated with specific criteria, to deeply examine the primary distinctions and regular uses of these four SCRs.
Unidirectional SCR: Fundamental and steady application core
Unidirectional SCR is the most fundamental and usual sort of thyristor. Its structure is a four-layer three-junction PNPN arrangement, consisting of three electrodes: anode (A), cathode (K) and gateway (G). It just enables current to stream in one direction (from anode to cathode) and activates after eviction is triggered. When switched on, also if the gate signal is eliminated, as long as the anode current is higher than the holding present (typically less than 100mA), the SCR stays on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and present resistance, with a forward repetitive top voltage (V DRM) of approximately 6500V and a rated on-state average present (ITAV) of approximately 5000A. For that reason, it is widely used in DC electric motor control, industrial heating unit, uninterruptible power supply (UPS) correction parts, power conditioning devices and other occasions that require continuous transmission and high power processing. Its advantages are easy framework, affordable and high dependability, and it is a core element of numerous typical power control systems.
Bidirectional SCR (TRIAC): Ideal for air conditioner control
Unlike unidirectional SCR, bidirectional SCR, additionally referred to as TRIAC, can achieve bidirectional transmission in both favorable and unfavorable half cycles. This framework includes 2 anti-parallel SCRs, which enable TRIAC to be activated and activated at any moment in the AC cycle without changing the circuit connection method. The symmetrical conduction voltage series of TRIAC is generally ± 400 ~ 800V, the optimum tons current has to do with 100A, and the trigger current is less than 50mA.
Due to the bidirectional conduction characteristics of TRIAC, it is specifically suitable for air conditioning dimming and speed control in home devices and consumer electronics. For example, devices such as lamp dimmers, fan controllers, and a/c unit follower rate regulatory authorities all depend on TRIAC to attain smooth power regulation. Additionally, TRIAC also has a lower driving power need and appropriates for incorporated design, so it has actually been widely used in smart home systems and small home appliances. Although the power thickness and switching rate of TRIAC are not like those of new power devices, its low cost and convenient usage make it a vital gamer in the area of tiny and moderate power AC control.
Gate Turn-Off Thyristor (GTO): A high-performance representative of active control
Gateway Turn-Off Thyristor (GTO) is a high-performance power gadget developed on the basis of standard SCR. Unlike ordinary SCR, which can only be shut off passively, GTO can be shut off actively by using a negative pulse current to the gate, therefore achieving more adaptable control. This function makes GTO do well in systems that require constant start-stop or fast response.
(Thyristor Rectifier)
The technical criteria of GTO reveal that it has incredibly high power handling capability: the turn-off gain is about 4 ~ 5, the maximum operating voltage can get to 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 performance signs make GTO commonly used in high-power circumstances such as electric engine traction systems, big inverters, commercial electric motor regularity conversion control, and high-voltage DC transmission systems. Although the drive circuit of GTO is relatively complex and has high switching losses, its performance under high power and high dynamic action needs is still irreplaceable.
Light-controlled thyristor (LTT): A reliable choice in the high-voltage seclusion atmosphere
Light-controlled thyristor (LTT) makes use of optical signals as opposed to electrical signals to trigger transmission, which is its biggest feature that distinguishes it from other types of SCRs. The optical trigger wavelength of LTT is usually between 850nm and 950nm, the action time is determined in milliseconds, and the insulation level can be as high as 100kV or over. This optoelectronic isolation system substantially improves the system’s anti-electromagnetic interference capability and safety.
LTT is mostly made use of in ultra-high voltage straight current transmission (UHVDC), power system relay security devices, electromagnetic compatibility defense in medical equipment, and army radar communication systems and so on, which have extremely high needs for safety and security and stability. For example, lots of converter terminals in China’s “West-to-East Power Transmission” project have adopted LTT-based converter valve components to guarantee secure procedure under extremely high voltage problems. Some progressed LTTs can likewise be integrated with gateway control to achieve bidirectional transmission or turn-off features, additionally increasing their application range and making them an optimal selection for fixing high-voltage and high-current control issues.
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