Which electrical phenomenon can be introduced into a power system by using VFDs?

Which electrical phenomenon can be introduced into a power system by using VFDs?

• A. Harmonics
• B. Voltage sag
• C. Power factor correction
• D. Inductive kick

Answer: (A)

Variable frequency drives introduce harmonic distortion into a power system because the drive’s input rectifier and high-speed switching inverter draw current in short pulses rather than a smooth sine wave. This nonlinear current draw injects harmonic components into the supply, creating voltages and currents at multiples of the fundamental frequency. These harmonics can cause transformer and motor heating, nuisance tripping, and other equipment performance issues, so they’re the classic phenomenon associated with VFDs. While VFDs can affect power factor and may cause brief voltage dips during startup, the defining effect of using VFDs is the introduction of harmonics. Inductive kick is a transient associated with inductive elements, not a typical result of VFD operation.

Variable frequency drives introduce harmonic distortion into a power system because the drive’s input rectifier and high-speed switching inverter draw current in short pulses rather than a smooth sine wave. This nonlinear current draw injects harmonic components into the supply, creating voltages and currents at multiples of the fundamental frequency. These harmonics can cause transformer and motor heating, nuisance tripping, and other equipment performance issues, so they’re the classic phenomenon associated with VFDs. While VFDs can affect power factor and may cause brief voltage dips during startup, the defining effect of using VFDs is the introduction of harmonics. Inductive kick is a transient associated with inductive elements, not a typical result of VFD operation.