Active Harmonic Filters – Dynamic THD Mitigation for Modern Industry

When your facility depends on dozens of variable frequency drives (VFDs), the risk of harmonic distortion (THD) rises quickly. Traditional passive filters may help under steady loads, but they can’t keep up when conditions change. The result? Voltage distortion, overheated equipment, nuisance trips, and costly non-compliance with IEEE-519 or utility harmonic limits.

That’s why more facilities are turning to Active Harmonic Filters (AHFs). These electronic devices continuously monitor the electrical system, detect harmonic currents, and inject equal but opposite currents to cancel them out in real time.

At Crossman Automation, we supply and integrate Danfoss Active Harmonic Filters and related solutions to deliver clean, reliable power across Western Canada’s toughest industrial sectors.

Why Active Harmonic Filters?

Unlike passive filters that are tuned to specific harmonic frequencies, active filters adapt to load changes instantly. This makes them ideal for facilities with many VFDs, varying production schedules, or fluctuating power conditions.

Key benefits of Active Harmonic Filters:

  • Dynamic THD Reduction: Maintain harmonic distortion under 5% across variable loads.

  • System Flexibility: One filter can protect multiple drives and nonlinear loads.

  • Power Factor Improvement: AHFs correct displacement power factor, reducing penalties.

  • Reliability: Prevents overheating of transformers, cables, and motors.

  • Compliance: Helps meet IEEE-519 and utility requirements, even on weak grids or generator systems.

How They Work

Active Harmonic Filters are installed parallel to the load. They use advanced electronics to:

  1. Measure harmonic currents in real time.

  2. Generate counter-currents that cancel unwanted harmonics.

  3. Stabilize voltage waveform, ensuring clean power reaches sensitive equipment.

Because they are adaptive, AHFs remain effective regardless of changes in drive loading, motor speed, or process conditions.

Applications for Active Harmonic Filters

Active Harmonic Filters are the best choice for:

  • Water & Wastewater Plants: Multiple pump drives with varying flow demand.

  • Mining & Aggregates: Crushers, conveyors, and mills with highly variable loads.

  • Oil & Gas: Generator-based power systems and drilling rigs.

  • Manufacturing: Facilities with robotics, sensitive controls, and fluctuating equipment usage.

  • Commercial Buildings: Hospitals, data centers, and campuses with HVAC, UPS, and IT loads.

Danfoss Active Harmonic Filter Solutions

Danfoss VLT® Active Harmonic Filter (AHF):

  • Reduces current distortion to below 5% at system level.

  • Supports multiple drives and nonlinear loads.

  • Improves displacement power factor to near unity.

  • Compact, cabinet-mountable design with high efficiency.

Paired with Danfoss drives—such as the VLT® AQUA Drive or VLT® HVAC Drive—these filters form an integrated harmonic mitigation package that keeps operations compliant and reliable.

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Active vs. Passive Filters

Feature

Passive Harmonic Filter

Active Harmonic Filter
Harmonic Reduction
10–15% typical
<5% across varying loads
Load Flexibility
Fixed, tuned to specific loads
Dynamic, adapts to changing conditions
Footprint
Bulky cabinets
Compact, scalable
Best Use Case
Stable, single-drive loads
Multi-drive, variable, sensitive sites


Crossman supplies both passive and active options, but when load conditions vary or compliance is critical, active filters are the superior solution.

Why Choose Crossman for Harmonic Solutions?

  • Expertise: Decades of experience in power quality and harmonic mitigation.

  • Partnerships: Direct relationship with Danfoss ensures access to the latest AHF technology.

  • Custom Engineering: We size, install, and integrate AHFs into your existing distribution system.

  • Local Support: Edmonton-based inventory and service for fast delivery across Alberta, B.C., and beyond.

  • Turnkey Solutions: From harmonic studies and compliance verification to installation, commissioning, and training.

Let’s Reduce Your Harmonics

If harmonic distortion is threatening your uptime, equipment, or compliance, Active Harmonic Filters offer a dynamic, future-proof solution. Crossman Automation can help you design and implement an AHF system that delivers clean, reliable power and long-term savings.

Contact us today to request a harmonic study or a quote on Danfoss Active Harmonic Filters—and take the first step toward eliminating THD from your facility.

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