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The TRIAC's gate can be connected through an opto-isolated transistor, and sometimes a resistor to the microcontroller, so that bringing the voltage down to the microcontroller's logic zero pulls enough current through the TRIAC's gate to trigger it. This ensures that the TRIAC is triggered in quadrants II and III and avoids quadrant IV where ...
Zero-crossing control (or burst-fire control) is an approach for electrical control circuits that starts operation with the AC load voltage at close to 0 volts in the AC cycle. [1] This is in relation to solid-state relays, such as TRIACs and silicon controlled rectifiers . [ 1 ]
A Triggering device is an electronic circuit, such as a Schmitt trigger, which is used to control another electronic circuit. Uses In many of industrial operations ...
Three-layer DIAC. The DIAC (diode for alternating current) is a diode that conducts electrical current only after its breakover voltage, V BO, has been reached momentarily. Three, four, and five layer structures may be used. [1] Behavior is similar to the voltage breakdown of a triac without a gate terminal.
The DIAC is the triggering device for the TRIAC. Thyristors are four-layer (PNPN) semiconductor devices that act as switches, rectifiers or voltage regulators in a variety of applications. When triggered, thyristors turn on and become low-resistance current paths. They remain so even after the trigger is removed, and until the current is ...
Phase-fired controllers take their name from the fact that they trigger a pulse of output at a certain phase of the input's modulation cycle. In essence, a PFC is a controller that can synchronise itself with the modulation present at the input.
Forward-voltage triggering occurs when the anode–cathode forward voltage is increased with the gate circuit opened. This is known as avalanche breakdown, during which junction J2 will break down. At sufficient voltages, the thyristor changes to its on state with low voltage drop and large forward current.
In AC circuits, SCR or triac relays inherently switch off at the points of AC zero cross when there is zero load current. The circuit will never be interrupted in the middle of a sine wave peak, preventing the large transient voltages that would otherwise occur due to the sudden collapse of the magnetic field around the inductance.