Voltage Flicker & Unbalance Study
Two related supply-quality problems assessed together: flicker, the visible light modulation caused by fluctuating load, and unbalance, the negative-sequence component created by uneven phase loading. Both are measured quantities with defined limits, and both damage equipment in ways that look like other faults.
What this study establishes.
Short-term and long-term flicker severity indices measured per IEC 61000-4-15.
Flicker source identification — welders, crushers, lifts, arc furnaces, large cycling motors.
Voltage and current unbalance factors calculated by the symmetrical component method.
Motor derating assessment per NEMA MG-1 for the measured unbalance.
Phase load redistribution plan where single-phase loading is the cause.
Mitigation options for flicker — supply stiffening, dynamic compensation or load smoothing.
What the work covers.
Two related supply-quality problems assessed together: flicker, the visible light modulation caused by fluctuating load, and unbalance, the negative-sequence component created by uneven phase loading. Both are measured quantities with defined limits, and both damage equipment in ways that look like other faults.
A small voltage unbalance produces a disproportionately large current unbalance in induction motors, because the negative-sequence impedance is low. A couple of percent of voltage unbalance is enough to force a meaningful derating and to shorten motor life materially.
What lands in your inbox.
Short-term and long-term flicker severity indices measured
Short-term and long-term flicker severity indices measured per IEC 61000-4-15.
Flicker source identification
Flicker source identification — welders, crushers, lifts, arc furnaces, large cycling motors.
Voltage and current unbalance factors calculated by
Voltage and current unbalance factors calculated by the symmetrical component method.
Motor derating assessment per NEMA MG-1 for
Motor derating assessment per NEMA MG-1 for the measured unbalance.
Phase load redistribution plan where single-phase loading
Phase load redistribution plan where single-phase loading is the cause.
Mitigation options for flicker
Mitigation options for flicker — supply stiffening, dynamic compensation or load smoothing.
How we run it.
Scope & data capture
We confirm the question the study must answer, agree the measurement or modelling points, and collect what the work depends on: identification of fluctuating loads and their duty cycles; phase-by-phase load measurement at the affected boards; motor inventory on the affected buses with rating and criticality.
Measurement & modelling
Engineers carry out the measurement and modelling on site and in software, under operating conditions representative of the problem rather than a single convenient snapshot.
Analysis against standard
Results are assessed against IEC 61000-4-15, IEC 61000-3-3 and IEC 61000-3-11, IEC 61000-2-4, with the assessment basis and any measurement uncertainty stated rather than implied.
Report & recommendations
You receive a signed engineering report with findings ranked by consequence, the reasoning behind each conclusion, and mitigation options costed so they can be acted on or deferred deliberately.
Assessed against the published limits.
Common questions.
Typically in one of these situations: visible light flicker, or complaints of screen flicker and eye strain; motors overheating on one site but not another with identical duty; heavy single-phase loading — ev chargers, welding, catering, small power. If none of these apply, the study is unlikely to be the right next step and we will say so.
To scope and run the work we need identification of fluctuating loads and their duty cycles; phase-by-phase load measurement at the affected boards; motor inventory on the affected buses with rating and criticality. Where any of it is missing we can establish it on site, which changes the scope rather than blocking the work.
Primarily IEC 61000-4-15, IEC 61000-3-3 and IEC 61000-3-11, IEC 61000-2-4, NEMA MG-1 §14.36. The applicable framework depends on your connection agreement and jurisdiction, so we confirm which applies before measurement rather than after.
Ready to start the engagement?
Tell us about your site and the problem you are seeing. We come back with a fixed scope, a fixed fee, and a named lead engineer.