How to select a choke (inductor) (part 3)
Continued from the article: How to select a choke (inductor) (part 2). We already introduced DC current and DC resistance. We know that the chokes (inductors) are typically rated in terms of maximum DC current, DC resistance, inductance, and a voltage rating. So we will explain inductance, and voltage rating below.
Inductance
As for the inductance value, this depends on how much filtering you want. The inductance and the filter capacitance forms a lowpass filter. The larger the inductor, the lower the cutoff frequency of the filter, and the better the rejection of the 120Hz (if full wave rectified) or 60Hz (if half wave rectified) AC component of the rectified DC.
Generally the larger the better. In fact larger inductances at low DC resistances mean larger chokes, which cost more money. Typically, 5-20 Henries is a good choice with the standard 32-50uF electrolytic capacitors.
The inductance and capacitance values also determine the transient response of the supply. This means the tendency for the supply to overshoot or "ring" with damped oscillations whenever a current transient is applied, such as at startup or on a heavy current surge, such as a hard "E" chord at full power.
Voltage rating
The voltage rating must be higher than the supply voltage, otherwise the insulation on the wire may break down, shorting the supply to the frame.
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You will be interested in this: Beginners' guide to choke
The series of articles will be interesting to you: Whether to have AC Reactor (AC Choke) or DC Link Choke for VFD (frequency inverter)
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