B44066D

Detuned reactors — antiresonance harmonic filter, B44066D series, 10 … 100 kvar · EPCOS AG / TDK Electronics

A power capacitor and the feeding transformer form a resonant circuit whether anyone intended it or not, and experience puts its self-resonant frequency between 250 and 500 Hz — right on top of the 5th and 7th harmonics that drives, UPS systems and electronic ballasts put onto the network. When that resonance is excited the current in both branches climbs, the capacitors and the transformer are overloaded, harmonics are amplified rather than absorbed, and metering, control systems and computers start misbehaving. The B44066D series prevents it. A three-phase reactor connected in series with each capacitor step moves the resonant frequency of that branch below the lowest harmonic present, so the branch is inductive to every harmonic above it and purely capacitive at 50 or 60 Hz, where the reactive power is actually wanted. Beyond that, the reactor and capacitor together form a series resonant circuit that offers a low-impedance path at its tuning frequency, so part of the harmonic current is drawn off the network rather than left to circulate. The series covers 10 to 100 kvar at 400 and 440 V in three detuning factors — 5.67 %, 7 % and 14 % — with high linearity, low losses and a temperature micro switch wound into the inner coil. Epkom's photographed unit is the B44066D7050M400: 7 % detuning, 50 kvar, 400 V, 50 Hz.