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STF Series Active Tracking Filters

Low voltage/high frequency noise is caused by everyday events such as turning on machinery, motors, or equipment. Although noise is less dramatic than high voltage transients, the long term effects of these frequent disturbances can be as damaging. Filtering systems such as Sola Active Tracking Filters provide clean AC power by eliminating lower voltage noise.

The Sola STF Series offers the original active tracking technology to guard against commonly occurring, but very damaging, lower energy transients. Offering excellent noise reduction, the filter continuously tracks the input AC power line and responds instantly upon detecting extraneous high frequency noise.

The STF Series eliminates low voltage/high frequency noise via a low-pass or L-C filter. These filters are used for low energy, high frequency noise reduction and consist of a series of inductors, capacitors and resistors. STFs are load dependent which means that the series inductors located on each phase and neutral conductors are sized to handle the maximum current draw on the line. These inductors together with the capacitors and resistors form a circuit capable of absorbing a large bandwidth of noise.

These devices are designed to meet UL 1283, and CSA C22.2 for Electromagnetic Interference Filters. STFs attenuate or reduce the amplitude of noise to a minimum of 40dB that occurs in a frequency range of 50KHz to 50MHz. STFs provide the industry’s best IEEE Category “A” protection, typically reducing normal mode transients to +/- 5 volts.

Built to meet your unique requirements, these filters are available in a multitude of voltage and phase configurations. They are hardwired and designed for years of trouble free operation requiring little or no operator intervention after installation.

Active Tracking® Filters are one part of a total power quality solution. They can be used alone or in conjunction with other Sola/Hevi-Duty products to solve more complex power quality problems.


  • Non degrading, series filter technology for total durability
  • High Frequency Noise filter, RLC Low-Pass filter
  • Attenuates noise to 40dB in frequency range of 50KHz to 50MHz
  • Hardwired connection
  • MTBF greater than 100,000 Hours, Mil 217F
  • UL 1283 Listed or
    Recognized (Single Phase models), CSA
  • Three Phase applications up to 200 Amp
  • Operating Temperature from -40°C to +45°C
  • Harmonic filtering
  • 10 Year Warranty

PDF Files

STF Series Active Tracking Filters Specifications
STF Series Active Tracking Filters Flyer
STF Series Active Tracking Filters Manual


STF Series Active Tracking Filters

Catalog Number Amps AWG Suggested Fuse/Circuit Breaker Ampacity
Suggest Max
Three-Phase Models (120/208 V WYE)*
Units are standard in NEMA 12 hinged enclosures
STF0150-10Y 15.0 14 15 18.75
STF0300-10Y  30.0 10 30 37.5
STF0500-10Y 50.0 4 50 62.5
STF1000-10Y 100.0 2 100 125
STF2000-10Y 200.0 3/0 200 250
Three-Phase Models (240 Delta)*
Units are standard in NEMA 12 hinged enclosures
STF0150-24D 15.0 14 15 18.75
STF0300-24D 30.0 10 30 37.5
STF0500-24D 50.0 4 50 62.5
STF1000-24D 100.0 2 100 125
STF2000-24D 200.0 3/0 200 250
Three-Phase Models (277/480 V WYE)*
Units are standard in NEMA 12 hinged enclosures
STF0150-27Y 15.0 14 15 18.75
STF0300-27Y 30.0 10 30 37.5
STF0500-27Y 50.0 4 50 62.5
STF1000-27Y 100.0 2 100 125
STF2000-27Y 200.0 3/0 200 250
Three-Phase Models (480V Delta)*
Units are standard in NEMA 12 hinged enclosures
STF0150-48D 15.0 14 15 18.75
STF0300-48D 30.0 10 30 37.5
STF0500-48D 50.0 4 50 62.5
STF1000-48D 100.0 2 100 125
STF2000-48D 200.0 3/0 200 250

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