Motors and Drives: Variable Frequency Drive (VFD)--Accessories

Part 8 of the Variable Frequency Drives Series explores accessories to protect variable frequency drives.


  • Input Fuses – Protect drive from excessive input current from line surges short circuits, ground faults. Recommended and may be required for UL installations

  • Line Reactors – Protects the drive from transient overvoltages (utilities switching), reduces input harmonics

  • EMI Filters – (ElectroMagnetic Interference Filter) reduces noise on the input side of the drive (required for CE applications). Drives are ONLY marked CE because they are used with these filters . Help prevent noise radiation to sensitive adjacent equipment.

  • RF Filters – aka Zero Phase reactors help reduce the noise radiated from the VFD wiring on the output side.

  • Braking Resistors – Needed to burn off excessive energy induced to the DC bus due to Back EMF during stopping.

  • Encoder Feedback Cards – Needed for better speed regulation and control

  • Communication Options

  • Software Configuration

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