# Voltage Regulation Calculator (ΔU%) Compute transformer or feeder voltage regulation from equivalent-circuit parameters: ΔU% ≈ (I·R·cosφ ± I·X·sinφ)/U·100. Returns both the approximate (linear) and exact (phasor) values; supports lagging, unity and leading power factor. > Canonical page: https://elysiatools.com/en/tools/voltage-regulation-calculator - **Category:** Math & Numbers - **Keywords:** voltage regulation, ΔU%, transformer, equivalent circuit, phasor diagram, IR drop, IX drop, power factor, leading, lagging, electrical engineering ## Overview The Voltage Regulation Calculator (ΔU%) computes the voltage regulation of a transformer or feeder line using equivalent-circuit parameters. By inputting the rated voltage, equivalent resistance, equivalent reactance, load current, and power factor, you can instantly determine both the approximate linear voltage drop and the exact phasor-based voltage regulation for lagging, unity, and leading loads. ## Inputs - **Rated Voltage U (V)** (number): Rated terminal voltage at the considered side (primary or secondary). - **Equivalent Resistance R (Ω)** (number): Equivalent series resistance (transformer winding or line). - **Equivalent Reactance X (Ω)** (number): Equivalent series reactance (leakage reactance or line reactance). - **Load Current I (A)** (number): e.g. 20 - **Power Factor cosφ** (number): 0 < cosφ ≤ 1. Ignored (forced to 1) when Load Type is Unity. - **Load Type** (select) - **Decimal Places** (number) ## When to use - When designing or analyzing electrical power distribution systems to ensure voltage drops remain within acceptable regulatory limits. - When evaluating transformer performance under varying load conditions and power factors. - When calculating feeder line voltage regulation to determine if conductor sizing or compensation is required. ## How it works - Enter the rated terminal voltage (U), equivalent series resistance (R), and equivalent series reactance (X) of the transformer or feeder. - Input the load current (I), power factor (cosφ), and select the load type (lagging, unity, or leading). - The calculator computes the IR and IX voltage drops, then applies both the linear approximation formula and the exact phasor diagram equations to output the voltage regulation percentage. ## Use cases - Determining transformer voltage regulation during commissioning to verify compliance with manufacturer datasheets. - Analyzing the impact of inductive motor loads on industrial feeder voltage stability. - Calculating voltage rise in distribution lines connected to solar inverters operating at leading power factors. ## Frequently asked questions ### What is the difference between the approximate and exact voltage regulation values? The approximate value uses a simplified linear formula, while the exact value uses phasor trigonometry to account for the phase angle shift under load. ### How does a leading power factor affect voltage regulation? A leading (capacitive) power factor subtracts the reactance term, which can result in a negative voltage regulation, indicating a voltage rise at the load. ### What does a negative voltage regulation percentage mean? A negative percentage indicates that the terminal voltage under load is higher than the no-load voltage, typically caused by capacitive loads. ### Can I use this calculator for three-phase systems? Yes, by using the equivalent line-to-neutral (single-phase equivalent) parameters and phase voltage. ### What is unity load type? 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