Introduction: Secret devices in power electronics
Silicon-controlled rectifiers (SCRs), additionally referred to as thyristors, are semiconductor power tools with a four-layer three-way joint structure (PNPN). Given that its introduction in the 1950s, SCRs have been commonly used in industrial automation, power systems, home appliance control and other fields because of their high hold up against voltage, big existing bring ability, rapid action and simple control. With the growth of modern technology, SCRs have actually advanced right into numerous types, including 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, but additionally determine their applicability in various application circumstances. This short article will start from a technological point of view, combined with particular specifications, to deeply analyze the major distinctions and normal uses these four SCRs.
Unidirectional SCR: Fundamental and secure application core
Unidirectional SCR is the most standard and common kind of thyristor. Its framework is a four-layer three-junction PNPN setup, including three electrodes: anode (A), cathode (K) and gateway (G). It only allows current to move in one direction (from anode to cathode) and activates after eviction is caused. Once switched on, also if eviction signal is removed, as long as the anode current is above the holding current (typically less than 100mA), the SCR continues to be on.
(Thyristor Rectifier)
Unidirectional SCR has strong voltage and existing tolerance, with an onward repeated optimal voltage (V DRM) of approximately 6500V and a rated on-state typical existing (ITAV) of as much as 5000A. Therefore, it is widely used in DC electric motor control, commercial heater, uninterruptible power supply (UPS) rectification components, power conditioning gadgets and other events that require continual transmission and high power processing. Its advantages are straightforward structure, low cost and high dependability, and it is a core element of lots of typical power control systems.
Bidirectional SCR (TRIAC): Suitable for air conditioner control
Unlike unidirectional SCR, bidirectional SCR, also called TRIAC, can achieve bidirectional conduction in both positive and adverse half cycles. This structure contains two anti-parallel SCRs, which allow TRIAC to be triggered and turned on at any moment in the AC cycle without altering the circuit connection approach. The in proportion conduction voltage variety of TRIAC is normally ± 400 ~ 800V, the optimum tons current has to do with 100A, and the trigger current is less than 50mA.
As a result of the bidirectional transmission attributes of TRIAC, it is particularly suitable for a/c dimming and speed control in family home appliances and consumer electronic devices. As an example, tools such as lamp dimmers, follower controllers, and ac unit follower rate regulators all rely on TRIAC to achieve smooth power regulation. Furthermore, TRIAC likewise has a reduced driving power requirement and appropriates for incorporated design, so it has been extensively used in clever home systems and tiny home appliances. Although the power thickness and switching speed of TRIAC are not as good as those of new power devices, its affordable and convenient use make it a crucial gamer in the area of tiny and average power air conditioning control.
Gateway Turn-Off Thyristor (GTO): A high-performance rep of active control
Gate Turn-Off Thyristor (GTO) is a high-performance power tool established on the basis of conventional SCR. Unlike regular SCR, which can only be shut off passively, GTO can be shut off proactively by applying a negative pulse present to the gate, thus achieving even more flexible control. This function makes GTO do well in systems that need regular start-stop or fast response.
(Thyristor Rectifier)
The technological criteria of GTO show that it has exceptionally high power dealing with capacity: the turn-off gain has to do with 4 ~ 5, the maximum operating voltage can get to 6000V, and the maximum operating current depends on 6000A. The turn-on time is about 1μs, and the turn-off time is 2 ~ 5μs. These efficiency indications make GTO widely made use of in high-power situations such as electrical locomotive grip systems, huge inverters, commercial electric motor frequency 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 dynamic action requirements is still irreplaceable.
Light-controlled thyristor (LTT): A reliable choice in the high-voltage isolation setting
Light-controlled thyristor (LTT) makes use of optical signals rather than electric signals to cause transmission, which is its largest feature that identifies it from other kinds of SCRs. The optical trigger wavelength of LTT is typically in between 850nm and 950nm, the response time is measured in nanoseconds, and the insulation level can be as high as 100kV or over. This optoelectronic isolation mechanism greatly enhances the system’s anti-electromagnetic disturbance capacity and safety and security.
LTT is mainly utilized in ultra-high voltage direct current transmission (UHVDC), power system relay security gadgets, electro-magnetic compatibility defense in clinical devices, and army radar communication systems and so on, which have incredibly high demands for safety and security and security. As an example, lots of converter stations in China’s “West-to-East Power Transmission” job have actually taken on LTT-based converter shutoff components to make sure steady operation under exceptionally high voltage problems. Some progressed LTTs can also be combined with gateway control to attain bidirectional transmission or turn-off functions, better increasing their application variety and making them an optimal choice for resolving high-voltage and high-current control problems.
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