Choke

Chokes for power applications are categorized into Alternating Current chokes (AC chokes) and chokes for Direct Current circuits (DC chokes).
AC chokes can be single or three-phase. Usually, these are choke coils with iron cores, with or without air gaps.
In the industry and universities, various terminologies are used to categorize chokes based on their application purposes:
Line Choke, Commutation Choke:
AC chokes for network fundamental frequency, mainly in a three-phase design, used to improve network current load (PFC) and to reduce the steepness of the flanks in the semiconductor valves of subsequent converters.
These chokes are primarily used in drive technology for a voltage drop uk = 4%, but uk = 2% is also common.
Motor Choke:
AC chokes, mainly three-phase, placed between the inverter output and the drive motor to shape the motor currents. These chokes extend the life of the motors and reduce noise. The required inductance values depend, among other things, on the length of the cables between the inverter and the motor.
Smoothing Chokes, DC-Link Chokes:
Direct current (DC) chokes, for example, for the DC link in converters between input rectifiers and output inverters. Also used for the excitation circuits of generators. The current dependency of this “smoothing element” must be considered in power supplies.
Compensation Chokes, Filter Chokes:
Filter chokes with matching capacitors, tuned to filter certain frequencies, or for (passive) compensation of reactive power loads.
Current-compensated Chokes:
These filter chokes have 4 (single-phase) or 6 connections (three-phase). They reduce asymmetric disturbances, influencing the useful signal only slightly.
Neutral Point Chokes:
Chokes for damping the currents and their steepness in the (via the choke) grounded neutral point in the case of earth faults in power supply networks (including railway power supplies).
Air Coils:
represent a special design. The advantage of their largely linear characteristic curve is offset by a large size and low inductance compared to iron core coils.

The essential characteristic of a choke coil is its inductance.
It must also be designed for the expected continuous and peak current. Instead of an inductance specification, a voltage drop at rated current can also be specified (see line chokes, uk…%). The rated frequency and the voltage to be considered for insulation technology are also required.