VFD & Motor Protection
Harmonic frequencies result from nonlinear electronic switching devices, such as variable frequency drives (VFDs), and flow into electrical systems causing increased wear and tear on motors, increased electrical usage and power quality problems.
Harmonic filters are designed to eliminate harmonic distortion caused by excess currents in and out of a VFD. They are made up of an array of inductors, capacitors and resistors that are capable of deflecting harmonic currents, sending them to ground. Passive harmonic filters are a series inductor-capacitor resonant circuit that is tuned to a specific frequency and connected with a VFD in parallel. The filter offers low impedance at the resonant frequency and sends the tuned harmonic to ground. Active harmonic filters are not designed for a specific situation as the passive filters, but can adjust dynamically to the demand for harmonic correction.
Line reactors protect VFDs from input power line disturbances by smoothing and slowing down incoming voltage distortion. They also reduce harmonics generated by the VFD that travel back into the power line. A line reactor is coil of wire that forms a magnetic field that current flows through. The magnetic field limits the rate of the rise of the current, reducing harmonics.
Load reactors are placed on the load side of a VFD to help protect motors from damage when noise spikes are produced along long cable lengths, which tend to amplify the noise. They also dampen the rate of the change of voltage that is applied to the motor windings, which improves motor performance.
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