Air-Core vs. Iron-Core Reactors: Structural Features and Power System Applications
Aug 01, 2026| With the rapid advancement and widespread application of power electronics, power supply systems face an increasing influx of nonlinear loads. These range from small-capacity household appliances to high-voltage, large-capacity industrial AC/DC static converters.
Because static converters operate via high-frequency switching modes, they frequently distort current and voltage waveforms within electrical grids, introducing severe harmonic pollution. To mitigate these power quality issues, electrical reactors serve as a critical defense mechanism.
By generating a controlled magnetic field as electric current flows through its conductor, a reactor provides essential inductive reactance to stabilize grids, filter harmonics, and limit short-circuit currents.
Key Structural Features of Dry-Type Iron-Core Reactors
Modern reactors are engineered to withstand intense thermal stress and mechanical forces. The structural performance of a premium
dry-type iron-core starting reactor relies on three main engineering highlights:
- Segmented Core with Precision Air Gaps: The core is manufactured from high-grade, cold-rolled silicon steel sheets. To ensure operational stability, the core legs are divided into uniform segments separated by multiple air gaps. These gaps are insulated with epoxy board and bonded using high-strength, high-temperature adhesives to prevent air gap distortion under load.
- Low-Noise End-Face Bonding: A high-performance silicon steel adhesive is applied to the core end-faces. This tightly bonds the laminations together, significantly reducing operational audible noise while providing superior corrosion resistance.
- High-Strength Wrapped Winding Coil: The primary coil insulation uses fiberglass impregnated with epoxy resin, cured through thermal baking, and finished with vacuum impregnation using high-temperature insulating varnish. This robust structure delivers excellent dielectric strength and mechanical endurance, protecting the reactor against thermal cycling, cracking, and massive inrush currents during motor startups.
Air-Core vs. Iron-Core Reactors: Direct Structural Comparison
Choosing the right reactor depends on your installation environment, space availability, and system requirements.
| Feature / Metric | Iron-Core Reactors (Dry-Type / Oil-Immersed) | Air-Core Reactors |
| Core Advantage | Compact footprint, low power loss, excellent EMC | Linear magnetic characteristics, strong short-circuit current limiting, low operational noise |
| Primary Limitation | Core saturates under high fault currents (losing current-limiting capability); noticeable noise | Higher power loss, bulkier physical footprint, requires careful electromagnetic spacing |
| Enclosure / Installation | Cabinet mounting (Dry-Type) or Outdoor (Oil-Immersed) | Outdoor or indoor open spaces (Not recommended for cabinet mounting) |
| Heat & Noise Control | Oil-immersed units offer superior heat dissipation and lower noise | Generates low acoustic noise but requires open spatial layout for natural air cooling |
Deployment Best Practices:
- Iron-Core Reactors: Dry-type epoxy-cast models offer exceptional dynamic and thermal stability, making them the preferred choice for indoor switchgear cabinet integration. Oil-immersed units feature slightly larger dimensions but provide superior heat dissipation and lower noise, making them ideal for outdoor substations.
- Air-Core Reactors: Designed without a magnetic core, these units deliver complete magnetic linearity and will not saturate under extreme fault conditions. Due to their external magnetic fields, they are typically installed outdoors in separated single-phase layouts (delta or in-line configurations) to prevent phase-to-phase short circuits. When space constraints require a stacked three-phase arrangement, the B-phase winding direction is reversed. This reverses its magnetic polarity, ensuring electromagnetic forces remain repulsive rather than attractive, thereby protecting support insulators from tensile stress during fault currents.
About Jinneng Electric Power Technology Co., Ltd.
Recognized as a National Pilot Enterprise for Technology Innovation and Application, Jinneng Electric Power Technology Co., Ltd. brings over a decade of expertise to global power distribution markets. We provide comprehensive, one-stop procurement solutions for high-performance reactors,capacitors switchgear components, and industrial electrical equipment.
Contact our engineering team today to source the right reactor solution for your power system project.