Back to News & Events The Real Cost of Harmonic Distortion
Modern factory floors look nothing like they did twenty years ago. You’ve got precision CNC machines, collaborative robots, high-speed vision systems, and networked PLCs all running simultaneously. These systems need clean power, but here’s the problem: the very drives and power supplies that enable this precision are generating electrical noise that can bring everything down.
If you’re an engineer or procurement manager specifying power systems for industrial automation, understanding Active Power Factor Correction (PFC) matters for a simple reason: it eliminates a major cause of unplanned downtime. It also cuts your energy costs and keeps you ahead of increasingly strict power quality regulations.
At Horizon PSS, we’ve spent decades supplying power to mission-critical applications. We’ve learned that Active PFC isn’t some nice-to-have feature. It’s what separates professional industrial power systems from everything else.
What Actually Creates “Dirty Power”
Standard rectifier-based power supplies pull current from the AC mains in sharp, narrow pulses instead of smooth waves. These pulses happen only at the peaks of the AC voltage cycle when the input capacitors are charging. The result? A heavily distorted current waveform loaded with harmonic frequencies (multiples of the 50Hz or 60Hz line frequency).
One machine doing this might not matter much. But put dozens of servo drives, VFDs, and switch-mode supplies on the same electrical panel, and the cumulative harmonic distortion becomes a real problem.
Total Harmonic Distortion: What the Numbers Mean
THD measures the ratio of harmonic content to the fundamental frequency. A pure sine wave has 0% THD. Power supplies without correction typically hit 70% to 150% THD. That means the harmonic content actually exceeds the fundamental current.
For anyone managing an automation system, high THD creates immediate operational headaches:
System instability shows up as intermittent PLC errors, false sensor triggers, and communication dropouts on industrial Ethernet or fieldbus networks. These “ghost” faults are a nightmare to troubleshoot because they’re inconsistent and disappear during static testing.
Thermal overload happens because harmonic currents increase the RMS current flowing through cables, transformers, and circuit protection. This generates heat beyond what the rated load predicts. Transformers take additional core losses. Neutral conductors in three-phase systems can see currents approaching 173% of phase current because of triplen harmonics (3rd, 9th, 15th) that add instead of canceling.
Protective devices trip unexpectedly. Circuit breakers and RCDs respond to RMS current, not just the fundamental. Harmonic content pushes devices over their trip threshold even when actual power consumption is well below rating. Production stops, and you’re left trying to diagnose it without proper power quality instrumentation.
Equipment ages faster. Capacitors in AC bus bars and motor drives don’t last as long when subjected to harmonic stress. Insulation systems degrade quicker from voltage distortion.
How Active PFC Solves This
Active Power Factor Correction uses a switched-mode boost converter at the power supply input to actively shape the input current waveform. A control IC monitors the AC input voltage continuously and adjusts the switching duty cycle to force the current to follow the voltage in phase and magnitude.
You get near-unity Power Factor (PF > 0.95) and THD below 5%. The power supply looks to the grid like a nearly ideal resistive load, drawing current smoothly throughout the entire AC cycle.
Why Active Beats Passive PFC
Passive PFC exists. It uses large inductors to filter harmonic content. But Active PFC gives you several advantages that matter in modern industrial applications:
Universal input range. Horizon’s Active PFC units run from 90 to 264VAC without manual switching or derating. If you’re building equipment for global markets, this eliminates voltage selector switches (and their failure modes). One SKU ships to North America, Europe, and Asia.
Better efficiency. Well-designed Active PFC stages hit 94% to 96% efficiency at the PFC stage alone. Less wasted energy means less heat. Lower internal temperatures improve MTBF for all components and reduce cooling needs in dense installations.
Smaller footprint. Operating at 50 to 100kHz switching frequencies, Active PFC inductors are dramatically smaller than 50/60Hz passive components. Horizon’s DIN-rail units with Active PFC take up minimal panel space. In modern compact enclosures where you’re fighting for every millimeter of rail space between power supplies, controllers, I/O modules, and safety relays, this matters.
Faster response. Active circuits respond to input voltage transients much faster than passive filters. You get better hold-up time during brief brownouts and sags (typically 20 to 30ms at full load). That’s enough to bridge typical utility disturbances without triggering a system reset.
IEC 61000-3-2 Compliance
The IEC 61000-3-2 standard (EN 61000-3-2 in Europe) sets limits for harmonic current emissions for equipment drawing up to 16A per phase. CE marking in the EU requires compliance. Other markets are increasingly following suit.
The standard defines four equipment classes:
Class A covers balanced three-phase equipment and miscellaneous equipment
Class B is for portable tools
Class C applies to lighting equipment
Class D includes equipment with “special waveform” (most IT and industrial power supplies under 600W)
Why Procurement Teams Should Care
Using non-compliant power supplies creates several risks:
Certification delays. Harmonic emissions get tested during EMC compliance testing. Fail the harmonic test and you’re looking at costly redesign, additional filtering components, and retesting. That can delay product launches by months.
Field failures. Even if you squeak through compliance testing, installed systems with multiple power supplies might exceed facility-level harmonic limits. Then you’re dealing with utility penalties or expensive mitigation hardware.
Obsolescence risk. Regulatory trends globally are moving toward stricter power quality requirements. Choose Active PFC now and your platform stays compliant as standards evolve.
Horizon PSS power supplies with Active PFC meet Class A and Class D requirements with margin to spare. You won’t need external line filters in most applications.
Power Factor vs. Efficiency (They’re Different)
People confuse Power Factor and efficiency all the time. They’re related but not the same thing.
Efficiency measures output power divided by input power. It’s the percentage of energy delivered to the load rather than wasted as heat.
Power Factor measures how effectively the equipment uses the current it draws. Low PF means high reactive or harmonic current that does no useful work but still flows through the distribution system.
Active PFC improves both, but the benefits differ. Higher efficiency cuts your electricity consumption. Higher Power Factor reduces infrastructure costs: smaller transformers, thinner cables, lower demand charges from utilities that penalize poor PF.
Hold-Up Time Matters More Than You Think
Here’s a benefit of Active PFC that doesn’t get enough attention: improved hold-up time. That’s how long a power supply maintains regulation after AC input loss. The boost converter in an Active PFC stage charges the bulk capacitors to 380 to 400VDC, well above the peak of 230VAC mains. This energy reservoir extends hold-up time significantly.
For industrial automation, 20ms of hold-up covers the transition between phases in automatic transfer switch (ATS) systems. It also bridges momentary interruptions from utility switching events. This prevents nuisance reboots of PLCs and HMIs that would otherwise stop production.
Panel Design Gets Easier
When you’re specifying power supplies for control cabinets, Active PFC changes your thermal calculations. The reduced harmonic current and higher efficiency mean:
Less heat. A 500W supply at 94% efficiency dissipates 32W as heat. An 85% efficient unit dumps 50W. In a sealed NEMA enclosure, that 18W difference can determine whether you need forced ventilation or can use natural convection.
Smaller upstream components. With PF approaching unity, input current is minimized. A 500W load at PF 0.95 draws about 2.3A at 230VAC. The same load at PF 0.70 draws 3.1A. You can use smaller circuit breakers, thinner wire, and lower-rated contactors. In large installations, that’s real money.
What Horizon PSS Offers
Industrial DIN-Rail Power Supplies
Our Active PFC DIN-rail units, including the Artesyn ADN-C series, are built for harsh industrial conditions:
Wide operating temperature range: -25°C to +70°C ambient without derating. These work reliably in non-climate-controlled environments.
High efficiency: Up to 94% typical efficiency keeps cabinet heat down.
Conformal coating options: Available for high-humidity and chemically contaminated atmospheres you find in certain industrial processes.
Global certifications: UL508, CE, CB scheme approval. No certification redundancy across markets.
Custom and Semi-Custom Development
For OEMs with specific mechanical integration needs or unique electrical specifications, we provide custom development. Our engineering team has designed Active PFC power systems for:
Ultra-compact chassis-mount configurations for space-constrained robotics controllers
Extended temperature range variants for outdoor automation equipment (-40°C to +85°C)
Modified hold-up time specifications for critical motion control applications requiring graceful shutdown
Customized output voltage and current combinations for proprietary motor drive architectures
Our NRE (Non-Recurring Engineering) process is transparent and schedule-driven. We maintain configuration control throughout the product lifecycle. That means obsolescence management and long-term availability commitments that catalog suppliers can’t match.
Starting With Clean Power
In factory automation, reliability starts at the AC input. Choosing power supplies with Active PFC isn’t about chasing trends. It’s about applying established engineering principles to eliminate a known source of system instability.
For procurement engineers evaluating suppliers, Active PFC is a clear technical differentiator. It shows a manufacturer’s commitment to power quality, regulatory compliance, and long-term system reliability rather than just meeting minimum specs at the lowest price.
At Horizon PSS, Active PFC is standard in our industrial power supply portfolio because we understand what mission-critical automation actually demands. Whether you’re designing a new production line or upgrading legacy equipment, we provide the technical expertise and products to ensure your automation infrastructure runs on clean, stable power.
Ready to eliminate harmonic distortion from your automation system? Contact Horizon PSS to discuss your application requirements. Our engineering team provides technical consultation, custom design services, and long-term supply partnerships for demanding industrial power applications.
