4. Product-Overview
User manual RHF-Active 16
4.2.1 RHF-Active
Non-linear Loads (e.g. frequency converter) load the mains with distorted (non-sinewave)
currents. Such currents increase losses in wires and transformers and cause distorted voltage,
which stress all connected loads in multiple manners (e.g. resulting in reduced lifetime). RHF-
Active measure the distorted currents and generate for each harmonic up 60th a phase shifted
compensation current. The sum of distorted load current and compensation current results in a
(nearly) sinewave grid current. The required nominal current of the RHF-Active depends on the
nominal current of the load and its distortion. If the distorting load is a frequency converter, the
percentage of compensation current is ca. 25-30%. This results in a grid current with mitigated
distortion of ca. 5%.
4.2.2 RHF-Hybrid
Especially for high loads (>>100kW) quite high level of compensation current is required. To
keep this level low, the RHF-Hybrid–System may be used. This system consists out of RHF-
Active added by one or two RHF-Passive. The RHF-Active controls usage of passive filter
circuits, resulting in several important advantages:
• Only ca. 10% of the nominal current are left for active compensation.
• The resulting distortion of the grid current may go down to less than 1% (THDi <1%).
• The total costs are significantly lower than by using exclusively active filters.
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