Introduction: Trick tools in power electronics
Silicon-controlled rectifiers (SCRs), likewise called thyristors, are semiconductor power gadgets with a four-layer triple junction structure (PNPN). Since its intro in the 1950s, SCRs have actually been extensively made use of in industrial automation, power systems, home appliance control and other fields due to their high endure voltage, big current carrying capability, rapid feedback and easy control. With the growth of technology, SCRs have actually advanced into several kinds, consisting of unidirectional SCRs, bidirectional SCRs (TRIACs), turn-off thyristors (GTOs) and light-controlled thyristors (LTTs). The differences between these kinds are not just mirrored in the framework and working concept, however additionally determine their applicability in different application circumstances. This post will start from a technological point of view, incorporated with certain criteria, to deeply assess the primary differences and typical uses of these 4 SCRs.
Unidirectional SCR: Basic and stable application core
Unidirectional SCR is the most basic and usual kind of thyristor. Its structure is a four-layer three-junction PNPN plan, consisting of 3 electrodes: anode (A), cathode (K) and entrance (G). It just permits current to flow in one direction (from anode to cathode) and activates after the gate is set off. As soon as turned on, even if eviction signal is gotten rid of, as long as the anode current is higher than the holding current (normally much less than 100mA), the SCR stays on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and existing tolerance, with an ahead repeated optimal voltage (V DRM) of as much as 6500V and a rated on-state typical present (ITAV) of approximately 5000A. Consequently, it is commonly made use of in DC motor control, industrial heater, uninterruptible power supply (UPS) rectification parts, power conditioning gadgets and other occasions that need continual conduction and high power handling. Its benefits are straightforward framework, affordable and high reliability, and it is a core part of several standard power control systems.
Bidirectional SCR (TRIAC): Ideal for AC control
Unlike unidirectional SCR, bidirectional SCR, also known as TRIAC, can accomplish bidirectional conduction in both favorable and negative fifty percent cycles. This framework consists of 2 anti-parallel SCRs, which permit TRIAC to be caused and activated any time in the air conditioning cycle without transforming the circuit connection method. The balanced transmission voltage range of TRIAC is usually ± 400 ~ 800V, the optimum tons current is about 100A, and the trigger current is much less than 50mA.
Due to the bidirectional conduction attributes of TRIAC, it is specifically suitable for air conditioning dimming and rate control in household home appliances and consumer electronic devices. For example, devices such as lamp dimmers, follower controllers, and a/c follower speed regulators all depend on TRIAC to accomplish smooth power law. On top of that, TRIAC additionally has a lower driving power need and is suitable for incorporated style, so it has been widely used in wise home systems and tiny devices. Although the power thickness and changing speed of TRIAC are not just as good as those of brand-new power tools, its low cost and convenient usage make it an essential gamer in the field of little and medium power a/c control.
Gateway Turn-Off Thyristor (GTO): A high-performance rep of active control
Gate Turn-Off Thyristor (GTO) is a high-performance power device developed on the basis of typical SCR. Unlike average SCR, which can only be switched off passively, GTO can be turned off actively by applying a negative pulse present to the gate, thus attaining even more versatile control. This attribute makes GTO carry out well in systems that need regular start-stop or fast reaction.
(Thyristor Rectifier)
The technical parameters of GTO reveal that it has very high power dealing with capability: the turn-off gain has to do with 4 ~ 5, the optimum operating voltage can get to 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 extensively used in high-power situations such as electrical locomotive traction 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 switching losses, its performance under high power and high dynamic reaction requirements is still irreplaceable.
Light-controlled thyristor (LTT): A trusted choice in the high-voltage seclusion environment
Light-controlled thyristor (LTT) utilizes optical signals rather than electrical signals to cause conduction, which is its greatest feature that identifies it from various other kinds of SCRs. The optical trigger wavelength of LTT is normally in between 850nm and 950nm, the response time is determined in split seconds, and the insulation degree can be as high as 100kV or over. This optoelectronic seclusion mechanism considerably boosts the system’s anti-electromagnetic disturbance capability and security.
LTT is generally utilized in ultra-high voltage straight existing transmission (UHVDC), power system relay protection devices, electro-magnetic compatibility security in medical equipment, and military radar communication systems etc, which have incredibly high requirements for safety and security and security. As an example, several converter terminals in China’s “West-to-East Power Transmission” project have embraced LTT-based converter valve modules to make certain stable operation under incredibly high voltage conditions. Some progressed LTTs can additionally be integrated with gateway control to accomplish bidirectional conduction or turn-off features, additionally expanding their application array and making them a suitable choice for addressing high-voltage and high-current control issues.
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