Motor starting reactor

FDUEG manufactures motor starting reactors to be installed on power lines up to 12 kV, rated for large motors up to tens of MVA of power. All designs, by IEC standard, fulfill the request of three starting instances within an hour, of which two are immediately consecutive. Heavier situations can be analyzed upon request.

Making use of a line reactor is an alternative to an autotransformer bearing the same functionality, in case it is needed to reduce the inrush current of a three-phase induction motor. This prevents the intervention of protection devices or a reduction in the network’s voltage.

When the appliance is started, the inductor bears a share of the supply voltage: due to the lower voltage dropped across the motor, it starts with a lower current and in a longer time. This hardly ever tops some tens of seconds, after which the reactor can be shorted through a contactor placed in parallel to it. The energy involved in this process is converted into heat only for a small share, with the rest being turned to reactive power that is not dissipated within the environment.

Motor Starting Reactor - 35 A - AN - 50 kg FDUEG
Motor Starting Reactor On 6.6 kV Line For 2 Consecutive Starts Of 40 Sec. 17.5-10.3-6.6 mH - 100 A - 50 Hz - AN - 130 kg FDUEG

Motor starting reactors for lines with voltage up to 12 kV features

A motor starting reactor works for a limited amount of time with a large ampere rating. Beside the thermal aspect related to quick overheating, the high currents involved require a careful mechanical design so that the inductor results resilient, in time, to the continuous and rapid stresses it is interested by.

FDUEG provides either air core or iron core reactors. The construction includes additional taps for electrical terminals connection, so that a single product allows to reduce voltage to many levels while feeding the cascaded motor. The number of taps and their performance can be tailored upon specific customers’ requests.

Custom design



Iron Core Reactors

The choice for iron core reactors is driven by a limitation in available dimensions, both for mechanical fitting and for magnetic field control.

The performance of an iron core is related to its saturation level. FDUEG designs these products to that the linearity is granted for any design condition, while also limiting the iron core losses not to cause local overheating.

The company makes use of a dry type VPI (Vacuum Pressure Impregnated) technology, for its simplicity and reliability. Supplying iron core oil filled reactors, contained in IP65 boxes, is also possible. All of FDUEG’s reactor can be placed in custom protection cabinets.

Air Core Reactors

Air core reactors can be chosen to control a motor’s start in case the installation area is wide enough to avoid that the generated magnetic fields impact on the surrounding’s apparatus.

Three-phase reactors are available in stacked coils configuration, so that the area occupied is minimized. Alternatively, FDUEG can produce single-phase models that are adequately insulated, with all the advantages a modular solution has.

An air core motor starting reactor is the ideal solution in case a bypass, once the start is complete, is not envisaged: the complete linearity of air, in fact, makes the reactor’s impedance constant independently of the flowing current.


Technical data

Iron core motor starting reactors
Up to 10 MW

Up to 12  kV

Air core motor starting reactors
Up to 10 MW

Up to 12 kV



Power Plants
fdueg applicazioni steelworks
Offshore Plants


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