Snubbers are circuits that limit the voltage and the rising ratio of off-state voltage during device turn-off. Because they do not require protection circuitry, 3Q devices are more efficient than standard triacs in applications with non-resistive loads. Three-quadrant (3Q) triacs can be triggered in only quadrants 1, 2, and 3. 4Q triacs must include additional protection components such as resistor-capacitor (RC) snubbers across the main terminals and an inductor that is in series with the device. Standard or four-quadrant (4Q) triacs can be triggered in all four modes. Because load current (armature speed) flows during both halves of the applied AC voltage, motors rotate smoothly at all rotational speeds. Typically, triacs are used to control motor speed. Once triggered, triacs continue to conduct current as long as there is current flow, even if there is no longer voltage at the gate terminal. For example, if the voltage from A1 to A2 is positive, then the gate trigger voltage is also positive. As a rule, the gate trigger voltage is the same polarity as the voltage through the triac. They also have two gates (G1 and G2), each of which triggers a corresponding anode. They have two anodes (A1 and A2) for conducting current in both directions. Triacs are three-terminal silicon devices that are configured in an inverse parallel arrangement to provide load current during both halves of the AC supply voltage.
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