Transformer economic capacity selection

This tool calculates the maximum symmetrical short-circuit current at the output of a transformer substation, based on IEC 60865 and IEEE C37.100 standards. Results are essential for selecting circuit breakers, fuses, busbars, and cables, as well as verifying equipment’s short-circuit withstand capability. Input Parameters Power Net Fault (MVA): Short-circuit power of upstream network, indicating source strength. Higher values lead to higher fault currents. Primary Voltage (kV): Rated voltage on the high-voltage side of the transformer (e.g., 10 kV, 20 kV, 35 kV). Secondary Voltage (V): Rated voltage on the low-voltage side (typically 400 V or 220 V). Transformer Power (kVA): Apparent power rating of the transformer. Voltage Fault (%): Short-circuit impedance percentage (U k %), provided by manufacturer. Key factor in determining fault current. Joule Effect Losses (%): Load loss as a percentage of rated power (P c %), used to estimate equivalent resistance. Medium Voltage Line Length: Length of MV feeder from transformer to load (in m, ft, or yd), affecting line impedance. Line Type: Choose conductor configuration: Overhead line Unipolar cable Multipolar cable Medium Voltage Wire Size: Conductor cross-section, selectable in mm² or AWG, with Copper or Aluminum material options. Medium Voltage Conductors in Parallel: Number of identical conductors connected in parallel; reduces total impedance. Conductor Material: Copper or Aluminum, affecting resistivity. Low Voltage Line Length: Length of LV circuit (m/ft/yd), usually short but significant. Low Voltage Wire Size: Cross-sectional area of LV conductor (mm² or AWG). Low Voltage Conductors in Parallel: Number of parallel conductors on the LV side. Output Results Three-phase short-circuit current (Isc, kA) Single-phase short-circuit current (Isc1, kA) Peak short-circuit current (Ip, kA) Equivalent impedance (Zeq, Ω) Short-circuit power (Ssc, MVA) Reference Standards: IEC 60865, IEEE C37.100 Designed for electrical engineers, power system designers, and safety assessors conducting short-circuit analysis and equipment selection in low-voltage distribution systems.

Calculate transformer turns ratio instantly with this professional online tool. Input any three of the following—primary voltage, secondary voltage, primary turns, or secondary turns—and get the missing parameter in real time. Built for electrical engineers and power system designers, it’s fast, accurate, and works on any device—no sign-up required. Primary Voltage ( V p ) : AC input voltage applied to the high-voltage winding (in volts). Secondary Voltage ( V s ) : AC output voltage from the low-voltage winding (in volts). Primary Turns ( N p ) : Number of conductor loops in the primary coil. Secondary Turns ( N s ) : Number of conductor loops in the secondary coil. All calculations assume an ideal transformer model—core losses, leakage flux, and resistance are neglected for theoretical accuracy in design-phase estimation. The calculator uses the fundamental transformer equation: V p /V s = N p /N s This ratio is critical in power distribution, isolation transformer design, and voltage adaptation for industrial equipment. For example: designing a step-down transformer from 480 V to 120 V with 800 primary turns yields exactly 200 secondary turns—enabling rapid prototyping and specification validation in real-world projects.

This tool calculates the required reactive power compensation for a distribution transformer to improve the system power factor and enhance efficiency. Power factor correction reduces line current, minimizes copper and iron losses, increases equipment utilization, and avoids utility penalties. Input Parameters Transformer Rated Power: The rated apparent power of the transformer (in kVA), typically found on the nameplate No-Load Current (%): The no-load current as a percentage of the rated current, provided by the transformer manufacturer. This value represents magnetizing current and core losses, which are key inputs for reactive power calculation Calculation Principle When operating under no-load conditions, a transformer consumes reactive power to establish the magnetic field in the core. This reactive power lowers the overall power factor of the system. By installing capacitors in parallel at the low-voltage side, part of this inductive reactive power can be compensated, thereby improving the power factor to a target value (e.g., 0.95 or higher). Output Results Required capacitor capacity (kvar) Comparison of power factor before and after correction Estimated energy savings and payback period Reference Standards: IEC 60076, IEEE 141 Ideal for electrical engineers, energy managers, and facility operators to evaluate capacitor bank sizing and optimize power system performance.

The cross-sectional area of the iron core is the result of a combination of power, material characteristics, and multi-physical field effects (thermal, mechanical, coupled fields), according to IEC 60076.