The induction regulator voltage-regulation field test measures the secondary output voltage of an operating induction regulator at three distinct tap or control positions: maximum raise, neutral (bypass or unity position), and maximum lower. The induction regulator is a transformer-like device with a moving contact arm that taps the secondary winding to vary the output voltage while the unit is energized and carrying load, so the test is conducted in the field with the regulator live and under actual or simulated load conditions. The three measured outputs are then checked for linearity - that is, whether the regulation progresses uniformly across the full control range without discontinuities, jumps, or dead bands that would indicate a sticking contact or a mechanical or electrical defect.
An induction regulator is expected to hold customer voltage within a contractual band as load and source voltage fluctuate throughout the day. If the regulator's output steps, stalls, or drifts nonlinearly across its control range, it cannot maintain steady voltage, and customers downstream will see sag or swell. A field test under load confirms that the regulator's movable tap contact is making solid electrical connection at every position, that the control mechanism is responding smoothly to its input signal, and that the windings are intact and delivering the rated voltage rise or drop at each tap. A result that deviates from linearity calls out a sticking contact, internal arcing, a broken or corroded lead, or a mechanical jam that could worsen if left in place.
Acceptance: the three-point voltage check is performed on a new or reconditioned induction regulator after it is first energized and allowed to stabilize, before the unit is released into full automatic load-following service, typically as part of the factory or field commissioning sequence. Maintenance: the same test is repeated on a periodic interval (commonly annual or at each major maintenance visit) or if symptoms such as customer voltage complaints, erratic control response, or a visible wiper-contact defect prompt an investigation. The regulator is tested at its actual rated voltage and, if possible, under its normal operating load.
With the induction regulator energized and stabilized under load (or under a simulated load large enough that a voltage change on the line will be observable in the secondary output), the operator sets the control or tap position to maximum raise and measures the secondary output voltage with a calibrated voltmeter, recording the reading. The control is then moved to neutral (unity or bypass position) and the voltage is measured again. Finally, the control is moved to maximum lower and the voltage is measured a third time. The three readings are plotted or tabulated, and the technician verifies that the voltage change between each adjacent position is approximately equal - that is, the regulation curve is linear across the full range rather than showing jumps, flats, or reversals that would signal a defect.
For each of the three control positions tested (maximum raise, neutral, and maximum lower): the secondary output voltage in volts, the date, time, and ambient temperature, the load current or simulated load condition at the moment each reading was taken, the regulator's rated voltage and regulation range in volts or percent, the manufacturer and model number, and the calibration due date of the voltmeter used. Any observations about the smoothness of control response, the condition of the wiper contact or tap mechanism, or any audible or visible arcing or sticking are noted alongside the readings.
NETA ATS-2025 section 7.12.1.2 and its maintenance twin in NETA MTS-2023 7.12.1.2.B.5 establish that the regulator's output voltage should be linear and continuous across the full control range from maximum raise through neutral to maximum lower. A result that meets this criterion - meaning the voltage change per unit of control movement is substantially the same throughout, with no dead bands, reversals, or sudden steps - is accepted as confirming the regulator's operation. A result showing nonlinearity, or an output voltage that does not match the nameplate regulation range, requires investigation and potentially service of the tap mechanism or internal contacts before the regulator is returned to unattended automatic service. See the purchased standard for the complete test procedure and any load-condition or ambient-temperature adjustments that may apply.
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