Active Power Calculator for DC and AC Circuits

This tool calculates the protected area between two lightning rods based on the IEC 62305 standard and the Rolling Sphere Method, suitable for building, tower, and industrial facility lightning protection design. Parameter Description Current Type Select the type of current in the system: - Direct Current (DC) : Common in solar PV systems or DC-powered equipment - Alternating Single-Phase (AC Single-Phase) : Typical in residential power distribution Note: This parameter is used to distinguish input modes but does not affect the protection zone calculation directly. Inputs Choose input method: - Voltage/Power : Enter voltage and load power - Power/Resistance : Enter power and line resistance Tip: This feature may be used for future extensions (e.g., ground resistance or induced voltage calculation), but it does not influence the geometric protection range. Height of Lightning Rod A The height of the primary lightning rod, in meters (m) or centimeters (cm). Usually the taller rod, defining the upper boundary of the protection zone. Height of Lightning Rod B The height of the second lightning rod, same unit as above. If the rods are of different heights, an unequal-height configuration is formed. Space Between Two Lightning Rods Horizontal distance between the two rods, in meters (m), denoted as (d). General rule: \( d \leq 1.5 \times (h_1 + h_2) \), otherwise effective protection cannot be achieved. Height of the Protected Object The height of the structure or equipment to be protected, in meters (m). This value must not exceed the maximum allowable height within the protection zone. Usage Recommendations Prefer equal-height rods for simpler design Keep spacing less than 1.5 times the sum of rod heights Ensure the protected object's height is below the protection zone For critical facilities, consider adding a third rod or using a meshed air-termination system

Calculation of voltage

Calculate resistance (Ω) from V, I, P, or Z in DC and AC circuits using Ohm’s Law. Includes power factor handling for real-world accuracy. “Tendency of a body to oppose the passage of an electric current.” This is the fundamental definition of resistance: the property of a material that resists the flow of electric current. Accurately calculating resistance is essential for circuit design, troubleshooting, and energy efficiency analysis—whether in direct current (DC) or alternating current (AC) systems. Who Is This Tool For? Electrical engineers : for load modeling, protection coordination, and pre-simulation parameter estimation. Electricians and field technicians : to quickly verify equipment resistance and diagnose short circuits, ground faults, or insulation degradation. Students and electronics hobbyists : to understand practical applications of Ohm’s Law across different circuit conditions. Energy auditors and efficiency consultants : to evaluate operational efficiency using resistance and power factor relationships. Automation and control engineers : for precise impedance matching in sensor loops or PLC input modules. Typical Use Cases Scenario Application Motor winding inspection Measure voltage and current to back-calculate equivalent resistance and detect inter-turn short circuits. Heating element verification Given rated voltage and power (e.g., 220V / 1500W), compute theoretical resistance to assess aging or failure. Lighting system design Calculate equivalent resistance of LED drivers or incandescent loads to ensure voltage drop stays within limits. UPS and inverter testing In single-phase AC output, combine apparent power and power factor to isolate the resistive component of the load. Educational labs Help students visualize why V/I ≠ R in AC circuits due to reactance and phase shift. Calculation Principle The calculator is based on Ohm's Law and its derived forms. Resistance (R) can be computed using any of the following equivalent formulas: R = V / I R = P / (I^2) R = (V^2) / P R = Z / Power Factor Where: R : Resistance (Ω) V : Voltage (V) I : Current (A) P : Power (W) Z : Impedance (Ω) Power Factor : Ratio of active power to apparent power, ranging from 0 to 1 Note: In AC circuits, these formulas are only fully equivalent when the power factor equals 1 (purely resistive load). Parameter Details Current Type Direct Current (DC) : Current flows steadily in one direction from positive to negative pole. Frequency is zero. In this case, impedance Z equals resistance R, and power factor is always 1. Alternating Current (AC) : Current direction and amplitude vary periodically at a constant frequency. Single-phase system : Two conductors — one phase and one neutral (zero potential). Two-phase system : Two phase conductors; neutral may be present in three-wire configurations. Three-phase system : Three phase conductors; neutral is included in four-wire systems. This calculator currently supports DC and single-phase AC inputs. For three-phase systems, convert line-to-line voltage to phase voltage first: V_phase = V_line / sqrt(3), then treat as single-phase. Voltage Voltage is the difference in electric potential between two points. Input method depends on system type: Single-phase : Enter Phase-Neutral voltage. Two-phase / Three-phase : Enter Phase-Phase voltage. Example: A standard 220V household outlet is single-phase → input 220V. An industrial 380V supply is three-phase → for per-phase calculation, use 380 / sqrt(3) ≈ 220V. Current Current is the flow of electric charge through a conductor, measured in amperes (A). It is one of the most direct inputs for resistance calculation via R = V / I. Power Electric power is the rate at which energy is supplied or consumed by a component, measured in watts (W). In AC systems, distinguish between: Active Power (W) : Real power that performs useful work. Reactive Power (VAR) : Power used to establish magnetic/electric fields; does no real work. Apparent Power (VA) : Vector sum of active and reactive power: S = sqrt(P^2 + Q^2). Important: The "P" in the formulas above refers to active power (W) . If you input apparent power (VA), you must also provide the power factor; otherwise, results will be inaccurate. Power Factor Power Factor = cos(phi), where phi is the phase angle between voltage and current. Pure resistive load (e.g., heater, incandescent lamp): Power Factor = 1 Inductive or capacitive loads (e.g., motors, transformers): Power Factor < 1 (typically 0.7–0.95) In AC circuits, resistance is derived from impedance and power factor: R = Z * Power Factor = Z / (1 / Power Factor) Impedance Impedance (Z) is the total opposition to alternating current flow, combining resistance (R) and reactance (X), measured in ohms (Ω). The relationship is: Z = sqrt(R^2 + X^2) Therefore, resistance can only be extracted from impedance if the power factor (or phase angle) is known. People Also Ask (FAQ) Why can’t I use R = V / I directly in AC circuits? Because V / I gives you impedance (Z) , not pure resistance (R). To get R, multiply by the power factor: R = (V / I) * cos(phi). Do I need to enter power factor for DC circuits? No. In DC, there is no phase shift, so power factor is always 1, and Z = R. Can I calculate resistance if I only know reactive power (VAR)? No. Resistance relates only to active power. You need either active power (W), or apparent power (VA) plus power factor. Can this tool be used for three-phase motors? Yes, but treat it per phase. Measure phase voltage and phase current, or convert line values using V_phase = V_line / sqrt(3), then apply single-phase formulas. Usage Tips Prefer voltage + current input : Most accurate and least prone to error. Ensure unit consistency : V in volts, I in amps, P in watts. Always enter power factor for AC : If omitted, the calculator assumes cos(phi) = 1, which overestimates resistance. Validate results : Example – a 1000W heater at 220V should have R ≈ (220^2)/1000 = 48.4 Ω. Large deviations suggest input errors. This tool adheres to international electrical standards (IEC 60050) and is suitable for education, engineering design, and field maintenance—helping users quickly and accurately determine the effective resistance in real-world circuits.

Calculate power factor (PF) in AC circuits using voltage, current, active power, reactive power, resistance, or impedance. Supports single-phase, two-phase, and three-phase systems. Based on IEC standards for electrical efficiency analysis. Input Parameter Symbol Unit Required Combinations Voltage V V (volts) With current → S = V×I Current I A (amperes) With voltage → S = V×I Active Power P W (watts) With S or Q → PF = P/S or P/√(P²+Q²) Reactive Power Q VAR With P → PF = P / √(P² + Q²) Resistance R Ω (ohms) With Z → PF = R / Z Impedance Z Ω (ohms) With R → PF = R / Z Definition and Importance Power factor (PF) is the ratio of active power (P) to apparent power (S) : PF = P / S = cosφ PF = 1.0 : Purely resistive load (e.g., heater), no reactive power PF < 1.0 : Inductive or capacitive load (e.g., motors, transformers) Low PF consequences : Increased line current Higher copper losses Reduced transformer capacity Utility penalties (common if PF < 0.85–0.90) Calculation Methods The calculator uses one of the following equivalent formulas based on available inputs: From P and S : PF = P / (V × I) From P and Q : PF = P / √(P² + Q²) From R and Z : PF = R / Z From phase angle φ : PF = cosφ (if angle is known) Note: DC circuits are not supported — power factor is always 1.0 in DC systems. System Support Single-phase AC Enter Phase-Neutral voltage and per-phase current. Two-phase AC Enter Phase-Phase voltage; assumes balanced load. Three-phase AC Enter Line-to-Line voltage (V LL ) and line current (I L ). The calculator assumes a balanced system and computes total apparent power as S = √3 × V LL × I L . Typical Applications Industrial motor systems : Verify PF before installing capacitor banks Energy audits : Identify low-efficiency loads for correction Electrical design : Size conductors and protection devices with accurate current estimates Utility compliance : Ensure PF ≥ 0.95 to avoid demand charges Educational labs : Demonstrate relationship between P, Q, S, and PF Usage Guidelines Use RMS values for voltage and current in AC systems For non-linear loads (e.g., VFDs, LED drivers), measured PF may include harmonic distortion effects If only apparent power (VA) is known, active power (W) must also be provided Resistance and impedance inputs assume linear, sinusoidal conditions Frequently Asked Questions (FAQ) What is the power factor and why is it important? The power factor (PF) is the ratio of active power to apparent power in AC circuits, indicating how effectively electrical energy is being used. A high PF means less wasted energy and more efficient use of electrical infrastructure. How do I calculate power factor if I only know voltage and current? To calculate power factor using just voltage and current, you need to measure or estimate the phase angle between them. The formula is: PF = cosφ, where φ is the phase angle. Alternatively, if you can also measure active power (P), then PF = P / (V × I). Can this calculator be used for DC systems? No, power factor is a concept applicable only to AC systems. In DC systems, the power factor is always 1 because there is no phase shift between voltage and current. What does a low power factor indicate about my system? A low power factor indicates that your system has significant reactive power, which means some of the electrical energy is being stored and then released by inductive or capacitive loads without doing useful work. This results in higher currents, increased losses, and possibly utility penalties. How can I improve the power factor in my facility? Improving power factor often involves adding capacitor banks to compensate for reactive power, especially in industrial settings with many motors. Reducing the number of lightly loaded inductive devices and ensuring proper maintenance of existing equipment can also help. Is this tool suitable for three-phase systems? Yes, this calculator supports single-phase, two-phase, and three-phase systems. For three-phase calculations, enter line-to-line voltage and per-phase current values. Ensure balanced load conditions for accurate results. Why might utilities charge extra fees for low power factors? Utilities may impose penalties on customers with low power factors because they require larger capacity infrastructure to deliver the same amount of active power. Low PF increases transmission losses and reduces grid efficiency. This calculator adheres to IEC 60050 terminology and is intended for use by electrical engineers, facility managers, technicians, and students in power systems analysis.