Science Fair Project Encyclopedia
This combination is frequently used to suppress the rapid rise in voltage across a thyristor, preventing the erroneous turn-on of the thyristor; it does this by limiting the rate of rise in voltage (dV/dT) across the thyristor to a value which will not trigger it. Snubbers are also often used to prevent arcing across the contacts of relays (and the subsequent welding/sticking of the contacts that can occur).
Another often seen form of a snubber is a simple diode placed in a circuit in parallel with an inductive load (such as a relay coil or electric motor. The diode is installed in the direction that ordinarily wouldn't allow it to conduct. When current to the inductive load is rapidly interrupted, a large voltage spike normally is produced in the reverse direction (as the inductor attempts to kep current flowing in the circuit). Placing the snubber diode in inverse parallel with the inductive load allows the current from the inductor to flow through the diode rather than through the switching element and the energy stored in the inductive load is dissipated in the series resistance of the inductor and the diode.Additional information is available in the Over-Voltage Protection section of the diode article.
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