This tool calculates the rating of protective devices (circuit breakers) for electrical circuits according to IEC 60364-4-43, providing protection against overloads and short circuits. Suitable for industrial, commercial, and building electrical design. Parameter Description Current Type Select the type of current in the circuit: - Direct Current (DC) : Constant flow from positive to negative pole - Alternating Current (AC) : Reverses direction and amplitude periodically at constant frequency System configurations: - Single-phase: Two conductors (phase + neutral) - Two-phase: Two phase conductors; neutral may be distributed - Three-phase: Three phase conductors; four-wire system includes neutral Voltage Electric potential difference between two points. - For single-phase: Enter Phase-Neutral voltage - For two-phase or three-phase: Enter Phase-Phase voltage Load Power to be considered when determining the characteristics of circuit components. Power Factor Ratio of active power to apparent power. Formula:cos φ = P / S where φ is the phase angle between voltage and current. Value ranges from 0 to 1. Method of Installation Installation method as defined in IEC 60364-5-52 (Table A.52.3). Examples include: - Free air - In conduit - Underground - Multiple circuits in a common duct Note: Not all installation methods are recognized in every country's regulations. Ambient Temperature Temperature of the surrounding medium when the conductor is not loaded. Affects current-carrying capacity; commonly referenced at 30°C or 40°C. Conductor Material of the conductor used: - Copper - Aluminum Different materials have different resistivity and current-carrying capabilities. Insulation Temperature rating of the insulation material: - PVC (Thermoplastic): 70°C at conductor - XLPE or EPR (Thermosetting): 90°C at conductor Higher temperatures reduce insulation performance and require derating. Wire Size Cross-sectional area of the conductor, typically in mm². Determines the maximum allowable current. Phase Conductors in Parallel Conductors with the same cross-sectional area, length, and material can be connected in parallel. The maximum permissible current is the sum of individual-core maximum currents. Circuits in the Same Conduit Number of lines inside the duct powering different loads (e.g., 2 lines for 2 motors). Reduction factors apply based on IEC 60364-5-52 Table B.52.17. Total Harmonic Distortion (THD) Total content of 3n harmonic current. If the value of total 3n harmonic distortion is unknown, use the total harmonic distortion value. High THD increases neutral current and affects breaker sizing. Protection Device Device responsible for protecting the cable from overload and short circuit, such as a circuit breaker or fuse. All Parallel Cables Are in a Single Conduit Check this option if all sets of parallel cables are installed in one duct (derating factor will be applied). Uncheck if each set is installed in a separate duct. Definition: One "set" consists of one conductor per phase + one neutral conductor (if required) + one protective conductor.