Detuned Reactor

Detuned reactors are critical components in power factor correction (PFC) systems operating within harmonic-distorted environments. These reactors are connected in series with capacitor banks and are designed to prevent resonance conditions that can otherwise occur between system impedance and capacitor reactance. Resonance not only amplifies existing harmonic currents but also exposes capacitors to electrical and thermal overstress, accelerating failure and degrading power quality. 

Rated Voltage

230 V / 400 V / 690 V / Custom up to 11 kV

Frequency Range

50 Hz ±5% / 60 Hz ±5%

Rated Current

Up to 1000 A continuous (customizable per application)

Inductance Value

Typically 0.15 mH to 5 mH (based on detuning percent)

Harmonic Attenuation

Tuned for 189 Hz (7%) / 134 Hz (14%) / application-specific

Product Description

Capacitor banks without detuned reactors tend to create parallel resonance circuits with the upstream power system at harmonic frequencies, especially the 5th and 7th. When resonance aligns with these harmonic orders, it leads to significant amplification of harmonic current into the capacitors, resulting in insulation failure, overheating, and elevated voltage distortion across busbars. Detuned reactors are specified with a tuning frequency typically set to 189 Hz (7%) or 134 Hz (14%) for 50 Hz systems. 

Insulation Class

Class H (180°C)

Dielectric Strength

3.0 kV AC for 1 minute (phase-to-earth)

Temperature Rise

≤ 90°C at rated load per IEC 60076

Core Material

Low-loss CRGO / Amorphous alloy core

Cooling Type

Natural Air Cooled (AN) / Optional forced air (AF)

Impedance Tolerance

±5% typical

Mounting Type

Base/floor mounted with vibration-dampening supports

Ambient Temperature Range

–10°C to +50°C (without derating)

Altitude Rating

Up to 1000 m above sea level (higher with derating)

Noise Level

≤ 65 dB at 1 meter distance

Protection Degree

IP00 / IP20 / Custom enclosures on request

Standards Compliance

IEC 60289, IS 5553, IEC 60076, IEEE C57.110

Technical Advantages

Capacitor dielectric systems are designed for sinusoidal voltage conditions and nominal current levels. The presence of harmonics in the system elevates the RMS current flowing through the capacitor, often exceeding the permissible thermal limit. When harmonic current is not mitigated, it contributes to dielectric heating and degradation of the polypropylene film insulation, leading to dielectric breakdown and shortened service life. 

Harmonics reflected back from PFC systems without detuned protection result in elevated I²R losses in transformers and cables. Harmonic currents, especially at 5th and 7th orders, increase eddy current losses in transformer cores and cause excessive heating in conductors due to skin effect and proximity effect. These thermal stresses often go unaccounted for in standard thermal design and result in premature derating or insulation aging. Detuned reactors mitigate harmonic re-entry into the upstream network by suppressing the resonance amplification that allows harmonics to circulate in the first place. 

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Industry Applications

Power Factor Correction Panels

Used in LV and MV APFC systems to prevent capacitor damage caused by amplified harmonic currents under resonance conditions. 

Variable Frequency Drive Systems

Limits harmonic interaction between VFDs and capacitor banks, avoiding resonance amplification and ensuring stable reactive power compensation. 

Steel Rolling Mills

Suppresses 5th and 7th harmonic resonance generated by arc furnaces and large drives during high-power, cyclic load operations. 

Commercial HVAC Installations

Prevents capacitor overheating from distorted waveforms caused by multiple chiller drives and fan systems operating on shared electrical networks. 

Automated Manufacturing Plants

Protects capacitors from harmonic overload in production environments with dense robotics, servo motors, and high-frequency switching equipment. 

Data Centers and Server Farms

Stabilizes reactive power compensation under continuous nonlinear loading from UPS systems, blade servers, and power supplies. 

 

System Expansion Without Resonant Frequency Shifts

When new nonlinear loads such as VFDs or rectifier banks are introduced into an existing electrical system, the aggregate harmonic profile changes. These changes can alter the system’s natural resonant frequency, leading to inadvertent alignment with dominant harmonic orders. Such alignment causes harmonic resonance and disrupts PFC operation.  

Detuned reactors are designed using low-loss CRGO or amorphous magnetic cores to reduce iron losses under continuous operation. The winding material is typically copper or aluminum with high thermal endurance insulation (Class H or F), designed for ambient conditions up to 50°C without derating. Typical detuning percentages range from 5.67% to 14%, selected based on harmonic analysis and target tuning frequency.  

Detuned Reactor

Having Doubts? Our FAQ

Check all our Frequently Asked Question

How does Frigate select the tuning frequency for detuned reactors in harmonic-rich systems?

Frigate performs a detailed harmonic spectrum analysis to determine the dominant harmonic orders present in the system. Based on this data, we typically tune reactors to 189 Hz (7%) or 134 Hz (14%) for 50 Hz systems. This avoids parallel resonance near the 5th or 7th harmonic. Our tuning ensures maximum attenuation without compromising the power factor correction performance. 

What construction features does Frigate implement to ensure thermal stability under harmonic loading?

Frigate uses Class H insulation materials for windings to handle elevated temperatures due to harmonic current heating. Our designs include low-loss CRGO or amorphous cores to minimize iron losses. All reactors are thermally rated for continuous operation at 1.1 times the nominal current. This ensures long-term stability even in high THDi (Total Harmonic Distortion current) environments.

How does Frigate ensure detuned reactors remain effective under varying load conditions?

Frigate uses non-saturating core designs to maintain linear inductance across fluctuating current levels. The inductance value is kept stable even when load varies, preventing resonance frequency drift. We also apply vacuum impregnation to reduce acoustic noise and mechanical vibration. This design approach maintains consistent harmonic filtering during system load changes. 

How does Frigate address detuned reactor integration into custom PFC panels?

Frigate provides application-specific reactor sizing based on reactive power demand and expected harmonic distortion levels. Each reactor is designed to match the capacitor rating and system impedance precisely. Mounting dimensions and connection terminals are tailored for panel builder convenience. Our integration support includes 2D/3D drawings and full thermal-impedance data sheets. 

What testing does Frigate conduct to validate detuned reactor performance before dispatch?

Frigate tests each reactor for impedance accuracy, insulation resistance, and high-voltage dielectric strength. We perform no-load loss tests and temperature rise evaluations under harmonic current simulation. Tuning frequency is verified with frequency response analysis. All tests follow IEC 60289 and IS 5553 standards for low-voltage power reactors. 

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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Operations Office

9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

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Detuned Reactor

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