{"id":1874,"date":"2026-07-06T08:59:59","date_gmt":"2026-07-06T00:59:59","guid":{"rendered":"https:\/\/cnbygele.com\/blog\/active-harmonic-filter-ahf-selection-guide\/"},"modified":"2026-07-06T14:59:16","modified_gmt":"2026-07-06T06:59:16","slug":"active-harmonic-filter-ahf-selection-guide","status":"publish","type":"post","link":"https:\/\/cnbygele.com\/fr\/blog\/active-harmonic-filter-ahf-selection-guide\/","title":{"rendered":"Guide de s\u00e9lection de filtre actif harmonique (AHF) pour ing\u00e9nieurs"},"content":{"rendered":"<div class=\"cnbyg-article\" style=\"max-width:820px;margin:0 auto;\">\n<p style=\"margin:0 0 16px;line-height:1.7;\">An <strong>active harmonic filter (AHF)<\/strong> injects cancelling current to reduce voltage and current distortion from nonlinear loads such as VFDs and rectifiers. This guide focuses on practical evaluation steps for U.S. industrial and commercial buyers\u2014measurement, documentation, and lifecycle support\u2014not generic marketing claims. Where equipment selection is involved, cross-check public specifications on cnbygele.com and confirm project-specific limits with your utility or consulting engineer. Section checklists can be reused as RFQ attachments and commissioning handover outlines.<\/p>\n<nav style=\"background:#f7f9fb;border:1px solid #e3e8ee;border-radius:8px;padding:14px 18px;margin:0 0 24px;\">\n<p style=\"margin:0 0 16px;line-height:1.7;\"><strong>On this page<\/strong><\/p>\n<ul style=\"margin:0 0 18px 1.2em;line-height:1.7;\">\n<li style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"#part-1-harmonic-assessment\">Part 1. Harmonic Assessment<\/a><\/li>\n<li style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"#part-2-apf--ahf-rating\">Part 2. APF \/ AHF Rating<\/a><\/li>\n<li style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"#part-3-integration-with-reactive-compensation\">Part 3. Integration with Reactive Compensation<\/a><\/li>\n<li style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"#part-4-documentation-and-handover-checklist\">Part 4. Documentation and Handover Checklist<\/a><\/li>\n<li style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"#part-5-commissioning-monitoring-and-long-term-op\">Part 5. Commissioning, Monitoring, and Long-Term Operations<\/a><\/li>\n<\/ul>\n<\/nav>\n<figure style=\"margin:26px 0;text-align:center;\"><img loading=\"lazy\" decoding=\"async\" style=\"max-width:640px;width:100%;height:auto;display:block;margin:0 auto;border-radius:8px;\" src=\"https:\/\/cnbygele.com\/wp-content\/uploads\/2026\/07\/active-harmonic-filter-ahf-selection-guide-cover-3.webp\" alt=\"Active harmonic filter AHF selection concept illustration\" width=\"640\" height=\"360\"\/><\/figure>\n<h2 id=\"part-1-harmonic-assessment\" style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Part 1. Harmonic Assessment<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Perform harmonic measurement at the PCC and at major nonlinear load feeders before sizing AHF.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Nonlinear loads draw current in pulses, creating harmonic currents that propagate through the distribution system.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">IEEE 519 is widely referenced in the U.S. for harmonic limits at the point of common coupling\u2014confirm applicability with your utility contract.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"https:\/\/cnbygele.com\/product\/ahf-active-harmonic-filter-harmonic-control-2\/\">active harmonic filters<\/a> inject opposing harmonic current to cancel distortion at the source or feeder level.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Capture nameplate data, single-line drawings, and utility interconnection rules in the RFQ package to reduce back-and-forth during technical review.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">If your site mixes linear motors and nonlinear electronics, treat harmonic and reactive targets as linked requirements rather than separate purchases.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Define acceptance criteria before shipment\u2014power factor, step response, or THD at agreed load points\u2014so commissioning disputes are less likely.<\/p>\n<div class=\"tip-box\" style=\"border-left:4px solid #2e7d32;background:#f3faf4;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Tip:<\/strong> Capture spectrum up to at least the 25th harmonic for industrial drives.<\/div>\n<h2 id=\"part-2-apf--ahf-rating\" style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Part 2. APF \/ AHF Rating<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\"><a href=\"https:\/\/cnbygele.com\/product\/ahf-active-harmonic-filter-harmonic-control-2\/\">Active power filter modules<\/a> are sized by harmonic current demand and desired THD target.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Passive tuned filters provide harmonic mitigation for specific orders but require careful resonance analysis with existing capacitors.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Detuning <a href=\"https:\/\/cnbygele.com\/product\/cksg-series-low-voltage-series-reactors\/\">series reactors<\/a> with capacitor banks shifts resonance away from dominant harmonic orders in some designs.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Neutral conductors in systems with triplen harmonics may carry higher current\u2014verify conductor sizing during design.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Capture nameplate data, single-line drawings, and utility interconnection rules in the RFQ package to reduce back-and-forth during technical review.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">If your site mixes linear motors and nonlinear electronics, treat harmonic and reactive targets as linked requirements rather than separate purchases.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Define acceptance criteria before shipment\u2014power factor, step response, or THD at agreed load points\u2014so commissioning disputes are less likely.<\/p>\n<table style=\"width:100%;border-collapse:collapse;margin:0 0 20px;\">\n<thead>\n<tr>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Factor<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Design input<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Outcome<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Load THD<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Measured amps by order<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Module count<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Redundancy<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">N+1 for critical sites<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Availability<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">CT location<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Feeder or main bus<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Stability of control<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<figure style=\"margin:26px 0;text-align:center;\"><img loading=\"lazy\" decoding=\"async\" style=\"max-width:640px;width:100%;height:auto;display:block;margin:0 auto;border-radius:8px;\" src=\"https:\/\/cnbygele.com\/wp-content\/uploads\/2026\/07\/active-harmonic-filter-ahf-selection-guide-body-3.webp\" alt=\"Active Harmonic Filter (AHF) \u2014 CNBYG product in industrial power facility (illustrative)\" width=\"640\" height=\"360\"\/><\/figure>\n<h2 id=\"part-3-integration-with-reactive-compensation\" style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Part 3. Integration with Reactive Compensation<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Coordinate AHF with capacitor banks to avoid resonance; hybrid panels are increasingly common.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Harmonic studies should list major nonlinear loads, operating duty cycles, and future expansion plans.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Maintenance includes filter fuse checks, thermal inspection, and verification that filter settings still match load changes.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Contact <a href=\"https:\/\/cnbygele.com\/contact-us\/\">CNBYG<\/a> for application review when THD targets are contractual or utility-driven.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Capture nameplate data, single-line drawings, and utility interconnection rules in the RFQ package to reduce back-and-forth during technical review.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">If your site mixes linear motors and nonlinear electronics, treat harmonic and reactive targets as linked requirements rather than separate purchases.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Define acceptance criteria before shipment\u2014power factor, step response, or THD at agreed load points\u2014so commissioning disputes are less likely.<\/p>\n<div class=\"tip-box\" style=\"border-left:4px solid #2e7d32;background:#f3faf4;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Tip:<\/strong> Keep as-built single-line diagrams updated after any feeder changes.<\/div>\n<div class=\"warning-box\" style=\"border-left:4px solid #f9a825;background:#fffbf0;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Important:<\/strong> AHF alone does not fix poor power factor if displacement PF is low\u2014may still need capacitors or SVG.<\/div>\n<h2 id=\"part-4-documentation-and-handover-checklist\" style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Part 4. Documentation and Handover Checklist<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Industrial acceptance should not rely on energization alone\u2014documentation proves ratings, safety, and maintainability for the next maintenance cycle.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Use the tables below as a starting RFQ checklist; your utility or EPC contract may require additional items.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">For product-specific datasheets, cross-check <a href=\"https:\/\/cnbygele.com\/product\/ahf-active-harmonic-filter-harmonic-control-2\/\">related CNBYG product pages<\/a> and request any missing type test excerpts.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Align factory acceptance tests with items your insurer or utility interconnection agreement may require.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">When comparing quotations, normalize currency, Incoterms, and included commissioning services before ranking suppliers.<\/p>\n<table style=\"width:100%;border-collapse:collapse;margin:0 0 20px;\">\n<thead>\n<tr>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Document \/ item<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Purpose<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">When to request<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Factory type test report<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Verify rated voltage, kvar, and temperature rise<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Before purchase order<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Single-line diagram template<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Panel layout and protection coordination<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Design phase<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Communication register map<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">BMS\/SCADA integration<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Before FAT\/SAT<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Spare parts list (5+ year)<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Lifecycle planning<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Contract negotiation<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Commissioning checklist<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Acceptance testing<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Before energization<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table style=\"width:100%;border-collapse:collapse;margin:0 0 20px;\">\n<thead>\n<tr>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Load type<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Typical THD concern<\/th>\n<th style=\"border:1px solid #d9e1e8;padding:9px 12px;background:#f4f7fa;text-align:left;\">Mitigation note<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Variable frequency drives<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">5th\/7th\/11th harmonics<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">APF or tuned passive filters per study<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">UPS \/ rectifier front-ends<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Broadband distortion<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Verify neutral loading in 3-phase systems<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">LED \/ SMPS clusters<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">High-frequency content<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Check aggregate current at PCC<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Legacy motor loads<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Lower harmonic share<\/td>\n<td style=\"border:1px solid #d9e1e8;padding:9px 12px;vertical-align:top;\">Reactive compensation may be primary need<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<div class=\"tip-box\" style=\"border-left:4px solid #2e7d32;background:#f3faf4;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Tip:<\/strong> Store factory test reports with the panel serial number for future warranty claims.<\/div>\n<div class=\"tip-box\" style=\"border-left:4px solid #2e7d32;background:#f3faf4;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Tip:<\/strong> Confirm imperial and metric dimensions if shipping to mixed-design sites.<\/div>\n<h2 id=\"part-5-commissioning-monitoring-and-long-term-op\" style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Part 5. Commissioning, Monitoring, and Long-Term Operations<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Commissioning should verify that reactive and harmonic targets are met at the point of common coupling, not only at the compensation cabinet terminals.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Functional tests typically include step response, power factor at defined load points, and harmonic readings compared to contract or IEEE 519 guidance where applicable.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Monitoring after energization helps catch hunting, unexpected resonance, or capacitor cell failures before they affect production uptime.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Train maintenance staff on lockout\/tagout, discharge timing for capacitors, and which alarms require immediate shutdown versus scheduled service.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Schedule a post-warranty review to reassess load changes\u2014production line upgrades often change compensation needs within three to five years.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Utility account managers can clarify whether PF adjustments affect demand charges only, energy charges, or both\u2014align KPIs before writing acceptance tests.<\/p>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Keep a spare-parts criticality list (fuses, contactors, fan assemblies, control boards) based on lead time and production impact, not catalog defaults alone.<\/p>\n<div class=\"tip-box\" style=\"border-left:4px solid #2e7d32;background:#f3faf4;padding:12px 16px;margin:0 0 18px;line-height:1.7;\"><strong>Tip:<\/strong> Log baseline power quality measurements after commissioning for future troubleshooting comparisons.<\/div>\n<h2 style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">Recommended CNBYG Products<\/h2>\n<p style=\"margin:0 0 16px;line-height:1.7;\">For project support, explore our <a href=\"https:\/\/cnbygele.com\/contact-us\/\">related product line<\/a>, <a href=\"https:\/\/cnbygele.com\/solution\/power-quality-system\/\">power quality system options<\/a>, and <a href=\"https:\/\/cnbygele.com\/about-us\/\">OEM\/ODM capabilities<\/a> on cnbygele.com.<\/p>\n<figure style=\"margin:26px 0;text-align:center;\"><img loading=\"lazy\" decoding=\"async\" style=\"max-width:640px;width:100%;height:auto;display:block;margin:0 auto;border-radius:8px;\" src=\"https:\/\/cnbygele.com\/wp-content\/uploads\/2026\/07\/active-harmonic-filter-ahf-selection-guide-product-2.webp\" alt=\"CNBYG harmonic product recommendation (illustrative scene)\" width=\"640\" height=\"360\"\/><\/figure>\n<h2 style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">FAQ<\/h2>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">How do you size an active harmonic filter (AHF)?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Measure the harmonic profile with a power quality analyzer over 24-72 hours, identify the dominant orders, and calculate harmonic current (for example 500 A total at 20% THD gives 100 A). Add a 20-30% safety margin, so a 100 A harmonic load points to about a 130 A AHF.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">Where should CTs be placed for an AHF?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Load-side (open-loop) CTs target specific noisy equipment, while source-side (closed-loop) CTs protect the whole system. Eaton and CoEpo guidance commonly recommend the load-side connection for both single and parallel systems.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">How many CTs does an AHF need?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">A three-phase system needs a minimum of two external CTs (on L1 and L2 with H1 facing the source); three CTs are required if line-to-neutral loads are present. CTs are typically rated 1.5-2x load current with a 5A secondary and 0.5 accuracy class.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">What THD limit does IEEE 519 target?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">IEEE 519 is the common benchmark, generally targeting total harmonic distortion (THD\/TDD) at or below 5% at the point of common coupling. Confirm the exact limits with your utility agreement.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">Do nonlinear loads need line reactors with an AHF?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Yes. Eaton&#8217;s manual recommends all harmonic loads have at least a 3% line reactor (or DC bus choke) to optimize filter performance and reduce resonance risk.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">How much safety margin should be added to AHF capacity?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Vendor guidance recommends a 20-30% margin above the calculated harmonic current, and rating the AHF at roughly 1.2x the peak harmonic current for the dominant orders, leaving room for load growth.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">Is AHF the same as APF?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">The terms overlap in industry; both use power electronics to inject cancelling current. Confirm harmonic order coverage and whether reactive\/unbalance features are included in the datasheet.<\/p>\n<h3 style=\"margin:28px 0 10px;font-size:1.15em;line-height:1.35;\">Does an AHF fix poor power factor?<\/h3>\n<p style=\"margin:0 0 16px;line-height:1.7;\">Not on its own if displacement power factor is low. An AHF cancels harmonics; you may still need capacitors or an SVG for reactive power, which is why hybrid designs are common.<\/p>\n<h2 style=\"margin:42px 0 14px;font-size:1.35em;line-height:1.3;\">References<\/h2>\n<ul style=\"margin:0 0 18px 1.2em;line-height:1.7;\">\n<li><a href=\"https:\/\/www.intonepower.com\/news\/ahf-sizing-guide-2025-calculate-active-harmonic-filter-size-for-i\/\" rel=\"nofollow noopener\" target=\"_blank\">Intone Power \u2014 AHF Sizing Guide<\/a><\/li>\n<li><a href=\"https:\/\/www.eaton.com\/content\/dam\/eaton\/products\/backup-power-ups-surge-it-power-distribution\/power-conditioners\/harmonic-correction-unit\/eaton-harmonic-correction-unit-instruction-booklet-IB156002EN.pdf\" rel=\"nofollow noopener\" target=\"_blank\">Eaton \u2014 Harmonic Correction Unit Installation Manual (PDF)<\/a><\/li>\n<li><a href=\"https:\/\/standards.ieee.org\/ieee\/519\/5488\/\" rel=\"nofollow noopener\" target=\"_blank\">IEEE Std 519 \u2014 Recommended Practice for Harmonic Control<\/a><\/li>\n<li><a href=\"https:\/\/wavetronics.eu\/7-essential-steps-to-choose-the-right-active-harmonic-filter-for-reliable-operations\/\" rel=\"nofollow noopener\" target=\"_blank\">Wave Tronics \u2014 7 Steps to Choose an AHF<\/a><\/li>\n<li><a href=\"https:\/\/www.coepowers.com\/how-to-calculate-the-size-of-an-active-harmonic-filter-apf\/\" rel=\"nofollow noopener\" target=\"_blank\">CoEpo \u2014 How to size an APF\/AHF<\/a><\/li>\n<\/ul>\n<p style=\"margin:0 0 16px;line-height:1.7;\"><strong>Ready to discuss your project?<\/strong> Contact <a href=\"https:\/\/cnbygele.com\/contact-us\/\">CNBYG engineering support<\/a> with your voltage class, load list, and target power factor or THD goals.<\/p>\n<\/div>\n<p><script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"How do you size an active harmonic filter (AHF)?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Measure the harmonic profile with a power quality analyzer over 24-72 hours, identify the dominant orders, and calculate harmonic current (for example 500 A total at 20% THD gives 100 A). Add a 20-30% safety margin, so a 100 A harmonic load points to about a 130 A AHF.\"}}, {\"@type\": \"Question\", \"name\": \"Where should CTs be placed for an AHF?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Load-side (open-loop) CTs target specific noisy equipment, while source-side (closed-loop) CTs protect the whole system. Eaton and CoEpo guidance commonly recommend the load-side connection for both single and parallel systems.\"}}, {\"@type\": \"Question\", \"name\": \"How many CTs does an AHF need?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"A three-phase system needs a minimum of two external CTs (on L1 and L2 with H1 facing the source); three CTs are required if line-to-neutral loads are present. CTs are typically rated 1.5-2x load current with a 5A secondary and 0.5 accuracy class.\"}}, {\"@type\": \"Question\", \"name\": \"What THD limit does IEEE 519 target?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"IEEE 519 is the common benchmark, generally targeting total harmonic distortion (THD\/TDD) at or below 5% at the point of common coupling. Confirm the exact limits with your utility agreement.\"}}, {\"@type\": \"Question\", \"name\": \"Do nonlinear loads need line reactors with an AHF?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. Eaton's manual recommends all harmonic loads have at least a 3% line reactor (or DC bus choke) to optimize filter performance and reduce resonance risk.\"}}, {\"@type\": \"Question\", \"name\": \"How much safety margin should be added to AHF capacity?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Vendor guidance recommends a 20-30% margin above the calculated harmonic current, and rating the AHF at roughly 1.2x the peak harmonic current for the dominant orders, leaving room for load growth.\"}}, {\"@type\": \"Question\", \"name\": \"Is AHF the same as APF?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"The terms overlap in industry; both use power electronics to inject cancelling current. Confirm harmonic order coverage and whether reactive\/unbalance features are included in the datasheet.\"}}, {\"@type\": \"Question\", \"name\": \"Does an AHF fix poor power factor?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Not on its own if displacement power factor is low. An AHF cancels harmonics; you may still need capacitors or an SVG for reactive power, which is why hybrid designs are common.\"}}]}<\/script><br \/>\n<script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@type\": \"BlogPosting\", \"headline\": \"Active Harmonic Filter (AHF) Selection Guide for Engineers\", \"description\": \"Select an active harmonic filter (AHF): harmonic order coverage, parallel modules, CT placement, redundancy, and APF integration for industrial power sites.\", \"keywords\": \"Active Harmonic Filter (AHF)\", \"inLanguage\": \"en-US\", \"author\": {\"@type\": \"Organization\", \"name\": \"CNBYG\"}, \"publisher\": {\"@type\": \"Organization\", \"name\": \"CNBYG\", \"url\": \"https:\/\/cnbygele.com\/\"}, \"mainEntityOfPage\": {\"@type\": \"WebPage\", \"@id\": \"https:\/\/cnbygele.com\/blog\/active-harmonic-filter-ahf-selection-guide\/\"}, \"url\": \"https:\/\/cnbygele.com\/blog\/active-harmonic-filter-ahf-selection-guide\/\", \"image\": \"https:\/\/cnbygele.com\/wp-content\/uploads\/2026\/07\/active-harmonic-filter-ahf-selection-guide-cover-3.webp\", \"datePublished\": \"2026-07-06\", \"dateModified\": \"2026-07-06\"}<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>S\u00e9lectionner un filtre harmonique actif (AHF) : couverture des harmoniques, modules parall\u00e8les, placement du TC, redondance et int\u00e9gration APF pour les sites industriels.<\/p>","protected":false},"author":3,"featured_media":1973,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_gspb_post_css":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-1874","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"blocksy_meta":[],"acf":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/posts\/1874","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/comments?post=1874"}],"version-history":[{"count":7,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/posts\/1874\/revisions"}],"predecessor-version":[{"id":1992,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/posts\/1874\/revisions\/1992"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/media\/1973"}],"wp:attachment":[{"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/media?parent=1874"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/categories?post=1874"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cnbygele.com\/fr\/wp-json\/wp\/v2\/tags?post=1874"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}