Harmonic-order analysis is useful before an APF RFQ when the spectrum is linked to a named electrical boundary and operating state. An unlabeled analyzer screenshot cannot show which loads were included, how the current reference was configured, or whether the capture represents the condition that the project intends to address.
For broader context, begin with the power quality system guides. This article explains how to assemble spectrum evidence for review; it does not prescribe a device size, order target, compliance result, or operating outcome.
Direct answer
Before requesting an APF review, keep individual-order data with the electrical boundary, units, capture period, operating state, CT reference, and meter settings. This lets another engineer determine what the spectrum represents before discussing a mitigation scope.
Part 1. Define the RFQ question before collecting a spectrum
Start with the electrical question the RFQ must answer. The project may concern a nonlinear-load feeder, a shared production bus, or a supply-side boundary. Those are different scopes, and the spectrum should be captured at the location that matches the decision.
Name the load groups expected to be included. Record the intended objective in plain language: characterize an existing condition, compare production states, or prepare a mitigation review. This avoids treating a spectrum from one cabinet as a description of an entire plant.
Important: Do not use a single spectrum to establish a complete APF scope without a documented boundary, load state, and acceptance method (IEEE 519 overview).
| RFQ question | Measurement boundary to name | Evidence needed |
|---|---|---|
| Understand one nonlinear load group | Defined input or local feeder | Load identity, meter position, CT and voltage reference |
| Compare a process feeder | Process distribution feeder | Operating-state log and coincident load inventory |
| Discuss a wider mitigation scope | Defined common or supply-side boundary | One-line diagram, time window, and responsibility for review |
Part 2. Preserve individual orders with their units
A useful export identifies each reported order and its units. Save the analyzer configuration, time aggregation, frequency reference, and current-reference information alongside the spectrum. A chart without these details is difficult to reproduce or compare.
Do not reduce the record to a statement such as “high harmonics.” Keep the original export, a readable table of the individual components, and notes explaining whether the values came from a representative interval, a peak interval, or an event capture.
| Spectrum field | Record with the export | Review value |
|---|---|---|
| Individual harmonic orders | Analyzer output and stated units | Shows the distribution rather than one unnamed percentage. |
| Time basis | Start, duration, and aggregation setting | Distinguishes a capture window from a trend. |
| Current reference | Meter setting and report label | Keeps comparisons on a known basis. |
| Event notes | Starts, transfers, switching, or bypass changes | Prevents an event from being mistaken for representative operation. |
The guide to APF sizing from measured harmonic current is a separate next step. It should follow a defined evidence boundary, not replace harmonic-order documentation.
Part 3. Compare operating states instead of screenshots
One production state may not describe another. Compare spectra from named operating conditions, such as normal production, a high-load run, partial line operation, start-up, or a known switching sequence. Use the same measurement point and configuration when comparison is the purpose.
Put an operating log beside the electrical export. Note active drive groups, rectifier or UPS load, process speed, capacitor state, bypass state, and source arrangement. A reviewer can then separate a stable operating profile from a momentary change.
| State to compare | Log beside the spectrum | Avoid assuming |
|---|---|---|
| Normal production | Line configuration and load groups | That it represents every shift or product. |
| High-load interval | Time window and coincident loads | That a short peak is the only design basis. |
| Start or transfer | Event and sequence note | That an event is steady-state behavior. |
| Capacitor or filter change | Switching state and affected feeder | That one device explains the entire spectrum. |
Part 4. Check the electrical boundary and measurement setup
The spectrum must identify where current and voltage were referenced. Mark the meter, CTs, voltage taps, incoming source, outgoing feeders, and any parallel or bypass path on the one-line diagram. Retain CT ratio and orientation, and keep the instrument settings with the exported data.
This documentation matters even when the spectrum appears clear. A changed CT reference or an included feeder can change what the record represents. The NEMA MG 1 overview gives general motor-system context, but it does not define a site-specific harmonic boundary or mitigation decision.
For a companion record checklist, see power quality metering before an RFQ. It helps organize inquiry inputs without substituting for engineering review.
Part 5. Turn a spectrum into a defined review scope
Spectrum evidence should inform a review, not become an automatic product instruction. An AHF/APF discussion needs the agreed harmonic-current objective, connection point, CT arrangement, representative records, existing equipment, protection coordination, room constraints, cable route, cooling, communications, and acceptance method.
The AHF Active Harmonic Filter page is a CNBYG product-line starting point when this scope is defined. It does not guarantee treatment of a particular order or a project result.
This boundary excludes several shortcuts. Do not select equipment from transformer nameplate data alone, a single local screenshot, an undefined order target, or a reactive-power-only objective. Where capacitor stages are present, harmonic impedance evidence may be another planning input rather than an afterthought.
Part 6. Build the APF RFQ evidence package
Package the spectrum so a reviewer can trace each record back to the plant condition. A compact, labeled set of evidence is more useful than a large collection of isolated images.
| Buyer should provide | Why it matters |
|---|---|
| One-line diagram and nominal system details | Defines the electrical boundary and supply context. |
| Meter, CT, and voltage-reference positions | Shows how the spectrum was acquired. |
| Individual-order exports with units and settings | Preserves the harmonic-order evidence. |
| Time windows and operating-state log | Connects the spectrum to plant operation. |
| Nonlinear-load inventory and existing filters/capacitors | Identifies the equipment included in the review. |
| Protection, space, cooling, cable, communication, and acceptance requirements | Defines integration and review limits. |
CNBYG can discuss product-line fit for a defined harmonic-current objective. Use the RFQ evidence package to start the conversation; this article cannot replace a network study or promise an APF outcome.
Frequently asked questions
What is harmonic order analysis?
It is the review of individual frequency components in a measured waveform or current record. The result is useful only when its location, units, capture settings, and operating state are retained.
Is one analyzer screenshot enough for an APF RFQ?
Usually not. A reviewable RFQ needs the electrical boundary, original exports, units, timing, meter and CT setup, operating-state log, load inventory, and integration constraints.
Which operating states should be compared?
Compare named states that matter to the decision, such as normal production, high-load operation, partial operation, start-up, transfer, or known switching changes.
Should a spectrum identify the measurement point?
Yes. The report should show the meter, CT, and voltage-reference location on a one-line diagram so the included loads and supply boundary are clear.
Can one dominant order select an APF?
No. A product review still needs the agreed harmonic-current objective, connection point, representative load record, CT arrangement, integration scope, and acceptance method.
What belongs in an APF RFQ package?
Send the one-line diagram, nominal system data, measurement setup, individual-order exports, time windows, operating log, load inventory, existing equipment, protection details, installation constraints, and acceptance requirements.
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