Abstract: Reactors, also called inductors, generate a magnetic field in a certain space when a conductor carries current. Therefore, all current-carrying conductors have inductance in a general sense.
How should reactors be selected for use with frequency converters ? The following analysis covers the selection of rated AC current, voltage drop, inductance, and the relationship between the inductance and cable length corresponding to the rated current.
1. Selection of rated AC current
The rated AC current is the long-term operating current of the reactor designed from the perspective of heat generation, while also taking into account sufficient high-order harmonic components. In other words, the actual current flowing through the output reactor is the output current of the inverter's motor load.
2. Voltage drop
Voltage drop refers to the actual voltage drop across the reactor coil at 50Hz and corresponding to the actual rated current. Typically, a voltage drop of around 4V to 8V is selected.
3. Selection of inductance
The rated inductance of a reactor is also a crucial parameter ! An inappropriate inductance selection directly affects the voltage drop under rated current, potentially causing malfunctions. The inductance depends on the cross-sectional area of the reactor core, the number of turns in the coil, and the adjustment of the air gap. The selection of the output reactor inductance is based on the cable length within the rated frequency range. Then, based on the actual rated current of the motor, the required core cross-sectional area and conductor cross-sectional area are selected to determine the actual voltage drop.
4. Inductance corresponding to rated current and cable length:
Cable length, rated output current, inductance
300 meters 100A 46μH
200A23μH
250A16μH
300A13μH
600 meters 100A 92μH
200A46μH
250A34μH
300A27μH
Ideally, the inductance of a reactor should remain constant at or below the rated AC current, and gradually decrease as the current increases.
When the rated current is greater than twice, the inductance is reduced to 0.6 times the rated inductance.
When the rated current is greater than 2.5 times, the inductance is reduced to 0.5 times the rated inductance.
When the rated current is greater than 4 times, the inductance is reduced to 0.35 times the rated inductance.
