Passive Harmonic Filters – Reliable, Cost-Effective THD Reduction

As more facilities adopt variable frequency drives (VFDs) to save energy and control processes, they also face the challenge of harmonic distortion (THD). Harmonics overheat transformers and cables, cause nuisance trips, and can lead to non-compliance with IEEE-519 or utility power quality limits.

For many applications, the most straightforward and cost-effective solution is a Passive Harmonic Filter (PHF).

Crossman Automation supplies and integrates Danfoss Passive Harmonic Filters—robust, tuned solutions that reliably reduce harmonics, improve power quality, and extend equipment life.

Why Passive Harmonic Filters?

Passive filters are built from reactors and capacitors, tuned to block or absorb specific harmonic frequencies generated by VFDs. Unlike active filters, they don’t require complex electronics—making them simple, rugged, and reliable.

Key benefits of Passive Harmonic Filters:

  • THDi Reduction: Cut harmonic current distortion to approximately 5–10%.

  • Compliance: Help facilities meet IEEE-519 and utility limits.

  • Reliability: Proven RLC designs with few components—low maintenance, long life.

  • Cost-Effective: Lower upfront investment than active filters or AFE drives.

  • Compact Design: Smaller footprint than active panels, easy to retrofit.

When to Choose Passive Filters

Passive harmonic filters are an excellent fit when:

  • Drives run at stable or predictable loads.

  • The facility requires simple, proven technology without advanced electronics.

  • Budget and footprint are primary considerations.

  • Harmonics must be mitigated to acceptable levels, but loads are not highly variable.

They’re ideal for pumping stations, HVAC systems, and single-drive applications where harmonics are a concern but loads don’t fluctuate dramatically.

Danfoss Passive Harmonic Filter Solutions

Danfoss VLT® Advanced Harmonic Filter (AHF 005 / AHF 010):

  • Cuts total harmonic current distortion (THDi) to approximately 5% (AHF 005) or 10% (AHF 010) at nominal load.

  • Designed to work seamlessly with Danfoss VLT® drives (AutomationDrive, AQUA Drive, HVAC Drive).

  • Compact and efficient, with >98% efficiency to minimize energy losses.

  • Rugged industrial construction, easy to mount and maintain.

These filters provide a practical balance of performance, simplicity, and affordability—making them one of the most widely used THD solutions in industry.

Passive vs. Active Filters

Feature

Passive Filter

Active Filter

Harmonic Reduction

~5–10% (fixed tuning)

<5% across variable loads

Load Flexibility

Best for stable, predictable loads

Adapts dynamically to changing loads

Complexity

Simple RLC design, low maintenance

Complex electronics, higher cost

Footprint

Compact, easy to retrofit

Larger, separate cabinet

Best Applications

Pumps, HVAC, single drives

Multi-drive plants, variable conditions

Crossman supplies both passive and active options—so we can recommend the best fit for your facility based on load profile, budget, and compliance requirements.

Industries That Benefit

  • Water & Wastewater: Pumping systems with predictable flow demands.

  • Commercial Buildings: HVAC drives and chillers in hospitals, offices, and campuses.

  • Manufacturing: Process equipment with consistent operating speeds.

  • Agriculture: Irrigation systems and compressor drives.

Whenever a facility uses VFDs under steady loads, passive harmonic filters are often the simplest path to compliance and reliability.

Why Choose Crossman Automation?

  • Partnership with Danfoss: Access to the proven VLT® AHF filter family.

  • Local Support: Edmonton-based inventory and service for fast turnaround across Western Canada.

  • Expert Guidance: We size and specify filters correctly based on your load and compliance requirements.

  • Comprehensive Solutions: If your system requires more flexibility, we can combine passive filters with active filters or recommend low-harmonic drives.

Let’s Filter Out Harmonics

Harmonic distortion doesn’t have to compromise your equipment or compliance. With Passive Harmonic Filters, you get a simple, cost-effective solution that just works.

Contact Crossman Automation today to request a quote or harmonic study, and find out if passive filters are the right choice for your facility.