Chokes are also a kind of inductor, but with the unique property of being able to help filter signals. Specifically, they can block high-frequency pulses while letting low-frequency pulses get through. When used, they reduce AC voltages to very small values and let the DC voltage pass through. Blocking or “choking” off the AC “ripples” from the radio frequencies and allowing for a steady DC power supply. The size of a choke is what determines its cutoff frequency or boundary, with larger chokes having lower cutoff frequencies and smaller chokes having higher cutoff frequencies. Chokes can be used for dimming, pulsing, microprocessor control, and other functions in applications that include line filtering, DC output filtering, oil and gas control systems, elevators/conveyors, robotics equipment, pumping equipment, UPS equipment, HVAC equipment, machine tool drives, variable frequency motor drives, and so on.
Power and audio frequency chokes have an iron core for greater inductance and filtering ability.
RF chokes use iron powder or ferrite beads and complex winding patterns that allow them to effectively operate at higher frequencies.