Electrical Power Reactors: Air Core Reactors and Iron Core Reactors

  • 29 May, 2019

In electrical power systems, reactors play many roles based on their types. Generally, they are classified according to their modes of applications. For instance: Shunt Reactor, Current Limiting Reactor, Damping Reactor, Tuning Reactor, Smoothing Reactor, etc. If constructional point of view is taken into consideration, reactors can be classified as:
• Air Core Reactors
• Iron Core Reactors

Air Core Reactors
This reactor is wound inductance equipment which makes use of one or more windings in parallel. Stranded cables of insulated aluminium are wound on the mandrel and the final coil is impregnated with epoxy resin and painted to provide a fine finish. These finished coils are mounted on station post insulators and galvanized steel structures, wherever necessary.

Damping reactors are typically air-core (or say ironless) reactors which are used for damping transient and inrush currents. When they are connected with the capacitor in series, they reduce inrush peak current flowing in the components to a value which won’t stress the insulation and doesn’t damage the internal connections of capacitor elements. They use natural cooling process (by air) and can be used indoors as well as outdoors. They are generally supplied in stacked, side-by-side or triangular configuration based on the physical and site constraints.

If we talk about air core dry type reactors, they are the ones which don’t utilize an oil insulation system or an iron core.

The best part about these types of reactors is that they are environment-friendly and don’t cause any fire hazard. On the downside, they come with high stray magnetic field which may interfere with other power equipment and produce eddy currents in nearby steel structures. But, these issues can be avoided if certain measures are taken during installation.

Iron Core Reactors
Iron core reactors generally consist of copper winding which is wound around an iron core that has an air gap. They are also called gapped iron core reactors. Factors such as the number of winding turns, air gap area and gap length determine the inductance of reactors. As the permeability of iron is high, the magnetic field stays confined to the core and desired inductance of the reactors can be completed with less winding turns.

When compared with air core reactors, iron core reactors have low stray magnetic fields. However, there is a saturation problem which means flux density of iron core reactors is limited and is also dependent on cross-sectional area. The higher the cross sectional area the higher the amount of flux they can carry. So, they should be designed in a way that they will not saturate when harmonic flux and fundamental flux is totally additive.

Both types of reactors have their own benefits and disadvantages. However, if they are designed, specified and installed properly, both of them will provide high performance.

For a variety of applications, many types of reactors are available in both categories – air core and iron core. So, depending upon your applications and requirements, make the selection of electrical power reactors accordingly.