Harmonic Filter Resistors Servicing Toronto and All of Canada

MegaResistors HFR Brochure 2021

A Harmonic Filter resistor (or damping resistor) reduces harmonic distortions in industrial power systems. These resistors are often combined with inductors and capacitors as a harmonic frequency filter.

We manufacture elements and enclosures to best meet your system’s power rating, inductance limits, and voltage requirements. Our filter resistors can have different protection ratings, including IP20, IP23, IP56 NEMA 1, NEMA 3R, NEMA 4 and NEMA 4X in galvanized steel, hot-dip galvanized steel, stainless steel and anodized aluminum enclosures. Additionally, our assembly offers options like post insulators and elevating stands, among many other options.

The Importance of Eliminating Harmonic Distortions

Harmonic distortions, caused by non-linear loads and varying power demands, can lead to various issues, including energy losses, overheating equipment, and premature aging of electrical components. These distortions can also cause malfunctions in sensitive electronic devices, disrupt communication signals, and lead to costly downtime. As a result, eliminating harmonic distortions maintains the efficiency and reliability of modern electrical systems.

By addressing harmonic distortions, businesses can ensure a stable and efficient power supply, reduce operational costs, and extend the lifespan of their electrical infrastructure.


In a normal AC power system, supply voltage varies sinusoidally with a fundamental frequency of 50 or 60 hertz (Hz). When linear loads are connected to the system, sinusoidal currents will be drawn from the system at the same frequency as the voltage.

However, when non-linear loads are connected, a series of sinusoidal currents (harmonics) will be drawn at integer multiples of the fundamental frequency, resulting in distortion of the fundamental signal. Harmonic filters are employed to mitigate, reduce and eliminate problems such as increased energy wastage, insulation failure and permanent damage to equipment.

Harmonic filters generally consist of capacitors and inductors tuned to resonate at a single frequency or through a band of frequencies. Adding a resistor to the filter allows greater tolerance of temperature changes in the components by damping the unwanted frequencies. It smoothens the filter’s response at the tuning frequency and widens the passband to cover a wider range of harmonics.

Certifications and Standards

Electrical Code Harmonic Filter Resistor Switchgear and Control Equipment Mechanical Structure
CSA 22.1
CIGRE 14-30
IEEE 1531
UL 508
C22.2 No. 14-05
C22.2 No. 94.1
NEMA 250
ANSI/IEC 60529
ANSI 2535.4

Ratings and Options

Basic Insulation Level Up to 1050 kV
Resistance We can supply any required resistance value
Power Up to 2MW
Application Indoor/Outdoor
Ambient Temperature -40° to + 60°C
Protection Degree NEMA 1 to NEMA 4X (IP20 – IP56)
Special Requirements Different transient power
Environmental Considerations Wind speed, Altitude, Seismic, Pollution


Applications Indoor/Outdoor
Enclosure Finish ANSI/ASA 61 Grey (Custom Enclosure finish is also available)
Enclosure Materials Galzanized Steel, Stainless Steel (304,316), Aluminum
Protection Degree NEMA 1, NEMA 3R, NEMA 4, NEMA 4X IP 20, IP 23, IP56


Our resistors are generally made for MV to HV voltage levels and can be used in:

  • HVDC conversion stations (LCC & SVC)
  • FACT Stations which may be used for:
  • Transmission voltage regulation
  • Power quality and transfer increase
  • Reactive power control
  • Reactive power control for MV motors (Mining)
  • Voltage stabilization (Wind farm)
  • Arc furnaces, rolling mills (Metal)


Our resistive elements have been designed specifically to meet the requirements of Harmonic Filters. We use specialized corrosion-resistant alloys with a low coefficient of change in resistance with temperature. Our resistive elements are flat to reduce inductance to a minimum and are arranged in banks insulated to 11 kV to reduce the space required for the typical industry requirements.


Enclosure Type HF-1 HF-2 HF-3
A 69” 69” 69”
B 77” 77” 101”
C 50” 85” 85”
Max Power 50kW 100kW 200kW
Note: Dimensions are without external Insulators



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