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DETUNING REACTORS

Design features
Our filter reactors are made of high-class transformer
sheets and copper wire or aluminium band.

They are dried and impregnated in a vacuum with environmen-
tally friendly, low-styrole resin which ensures they can with-
stand high voltages, have low noise levels, and offer a long
operating life.

Depending on their rated power, the reactors are provided with
either terminal blocks or terminal lugs/cables. The connection
of the aluminium reactors is made through copper terminals as well, which are reliably connected with the aluminium band by a
special, well-proven welding method.

High-class iron cores with multiple air gaps as well as a staid designing approach guarantee high current linearity and low
heat dissipation losses, at the same time allowing for compact dimensions and competitive cost. Compared with low-end
reactors, our FK-Dr may save up to 100 Watts of heat dissipation losses per piece, a very important factor for the long-term
operational cost (and amortisation) of the equipment.

High insulation class or low temperature rise?
Other than certain manufacturers which take special pride in offering their reactors with insulation class ratings for operation
DETUNING REACTORS the capacitor. In most cases, reactors are placed in close vicinity of the capacitor, and should therefore not serve as a destruc-
at temperatures of up to 165°C or even beyond, we focus on the operating environment of the the application’s key component:
tive heat source. The conservative layout of our reactors is to limit the maximum temperature of the reactor to 115°C under
rated operating conditions. An integrated reversible thermal switch allows external monitoring for disconnection of the reactor
in the event of impermissible buildup of heat (>125°C).

How to avoid ferro-resonance
Commercial pressures and the desire for ever smaller switchgear dimensions lead to an increasingly intense utilisation of sys-
tems and components. Even the detuning reactors have become more compact, which has been accompanied by a reduction of
their internal resistance.
Despite excellent linearity of inductance at high currents - usually the most important criterion when evaluating reactors - pro-
blems may occur in operation under unknown mains conditions. e.g. insufficient damping (low impedance) by upstream switch-
gear components, even at relatively low levels of harmonic distortion. Due to the magnitude of the initial switching current, the
inductance of the reactor may break down to a fraction of its nominal value. In these cases, the core becomes saturated; strong
audible humming and currents exceeding the rated current can occur. This phenomenon is also called Ferro-resonance.
As the use of adequately sized reactors with higher load capability is usually ruled out for cost and space considerations, the
use of capacitor contactors with inrush protection is recommended in all cases where the mains conditions are not known
exactly. These can provide a damping effect which substantially exceeds that achieved by adaptation of the reactor dimensions,
and at a much reduced cost.

It should be noted that, even when using capacitor contactors with inrush protection, sufficient current linearity of the reactor
must be provided in accordance with its operating conditions.

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