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Global Manufacturer of Metal-Enclosed Capacitor & Harmonic Filter Banks

Elgin acquired Gilbert Electrical Systems in 1991, which provided a deeply experienced engineering staff with a track record of building the highest quality metal enclosed capacitor and filter banks. Fast forward to 2021, Elgin has delivered hundreds of metal enclosed capacitor and harmonic filter banks to utilities and industry around the world. Our capabilities range from small pad mounted cap banks to large multi-stage banks over 100 MVAR. Elgin manufacturers out of its 100,000 sqft manufacturing facility located in West Virginia and has a dedicated field service staff to assist with installations and service.

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Enclosed Capacitor Banks - Up to 35kV

Capacitor banks are designed and built to improve performance and efficiency of electrical systems.  Elgin Power Solutions’ medium voltage, metal-enclosed capacitor banks not only provide added protection for your equipment, but are cost-effective, flexible, predictable, and easy to maintain.  Our capacitor banks are custom built to customer requirements and are shipped factory tested, assembled, and ready for interconnection.  Enclosures contain all switching, protection, safety features, and control.  When compared to an “open-rack” capacitor bank, metal-enclosed banks save money as they are easier and faster to install, commission, maintain, and they take up less space.

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Enclosed Capacitor Banks - Features & Benefits 


  • Fixed, single-step and multi-step capacitor banks.
  • Can Be placed in an indoor or outdoor environment.
  • Low voltage protection and control equipment is installed in a separate, easily accessible compartment.
  • Medium voltage incoming section and stages is in separate compartments for ease of access and maintenance.
  • Banks are programmed to provide site-specific power factor and voltage mitigation.
  • Banks come factory pre-assembled, tested and ready for fast installation and interconnection.
  • Enclosure made with whichever type/grade of steel or aluminum is specified.
  • Standard Powder Coat Finish on all enclosures.


  • Free up the power capacity of the facility.
  • Simpler engineering and installation than open-rack design.
  • Improve voltage profile and power factor.
  • Reduce apparent current and system losses.
  • Provide reactive energy required by inductive loads.  
  • Avoid penalties due to poor power factor.

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Enclosed Harmonic Filter Banks

Elgin Power Solutions’ metal-enclosed harmonic filter banks are designed for medium voltage power factor correction, voltage support, mitigation from harmonic distortion, and prevention from risks of resonance.  Elgin’s harmonic filter banks are configurable as fixed or automatic, with one or more stages at nominal voltages from 2.4 kV to 35 kV.  Available filter types include C-type, High-Pass, detuned, single-tuned, and multi-tuned.  Each unit is packaged in our high-quality enclosures that come with standard powder coat paint making them the most durable in the industry.

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Enclosed Filter Banks - Basic Design & Operation Principle

The basic combination of capacitors and inductors forms a tank circuit, which provides a low impedance path for the targeted harmonic frequency.  The idea is to properly size the LC circuit with respect to its location in the system to achieve the same resonance frequency of the harmonic to be eliminated.  In other words, unwanted harmonics are diverted into the filter, preventing them to flow into the power source.  As a result, the harmonic current is dissipated as heat by the passive harmonic filter instead of being exported to the utility system and other end-users.  However, this heat dissipation should not be considered a loss due to the harmonic filters as it already existed in the system in unusable frequencies.  

Elgin ensures the ratings of capacitors and reactors to be used as a filter are properly selected based on the following technical parameters:

  • Harmonic order to be removed;
  • Harmonic profile tof the load current;
  • kVA requirements of the load;
  • Harmonic factor of neutral current; and
  • System data and configuration (i.e., power factor, one-line diagram).

Additionally, Elgin will perform a detailed power quality study to assure that connection of the shunt passive harmonic filter will not cause a resonance condition on the power system, as harmonic resonance can result due to the magnification of certain harmonic frequencies.

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