Inverter With Ac Reactor Or Dc Reactor?

In a frequency converter, is the AC Reactors more important than the DC choke? What effect does the lack of an AC mains choke have on the inverter? What about the DC choke?

Good quality frequency converters contain either an AC choke or a DC choke (choke). Including them in the basic design of the frequency converter allows the design engineer to maximize the benefits of the choke. Their function is to reduce the current distortion caused by the input stage rectifier by slowing the rate of change of the current, thereby charging the internal capacitors at a lower rate over a longer period of time.

The harmonic distortion caused by the frequency converter is related to the size and load of the frequency converter, the size of the choke, and the supply network parameters.

Without an AC choke or a DC choke, the harmonic distortion will be greater.

Another consideration should be a properly sized source transformer that provides adequate impedance. A large power transformer used as an isolation transformer (although more of an investment) should provide 3% to 5% impedance while also providing voltage transient mitigation, reducing pulse peaks by a factor of 10 to 1, and reducing noise by using an AC Delta primary to Wye secondary, center tapped to ground. It provides additional protection for the front end (inverter) end of the VFD, while proper grounding between the signal source and the VFD, the VFD and the motor, and the motor and the voltage source helps mitigate high frequency noise, especially when a flat braid is used as the ground wire. This protects your investment and helps prevent the VFD from generating noise that could harm nearby instrumentation and PLC power supplies, etc. In addition, you can tap the transformer, allowing for higher input voltages, mitigating issues caused by voltage drop high impedance.

The DC link helps mitigate DC bus ripple and increases input impedance, which can slow power-up inrush and sudden demand current requirements, thus extending capacitor life, while the large power transformer protects the front end of the VFD by providing voltage noise protection and increasing input impedance to make the current smoother, and adding the ability to change taps to prevent voltage sag, while the input reactor slows the inrush current, thus extending input component and capacitor life, but does not provide voltage pulse or noise protection to the drive converter components, and increases voltage drop, adding stress to these components. The important thing to remember is that "proper" system design protects your VFD and system component investment.