Engineering calculators

DC and AC resistance of a rectangular busbar including skin effect, with the exact strip solution and the perimeter-shell approximation side by side.

Conductor temperature of a busbar in still air, solving loss, convection and radiation together instead of assuming a current density.

Continuous current rating of a power cable by the IEC 60287 thermal method, computed from geometry and soil conditions rather than read off a table.

Constriction resistance of a bolted busbar or terminal joint from Holm theory, with the surface film term that usually decides whether a joint ages well.

Voltage drop along a cable or busbar run for DC, single-phase and three-phase supplies, separating the resistive and reactive contributions.

A 630 A, 400 V three-phase busbar riser designed end to end - temperature rise, AC resistance, voltage drop, joint resistance, cooling cross-check and insulation distances - with every step pre-loaded into a calculator.

RMS capacitor current, output voltage ripple split into capacitive and ESR parts, ESR loss and self-heating for a continuous-inductor converter output.

Peak, valley, ripple and true RMS inductor current for buck, boost and buck-boost converters in CCM, with the critical inductance for the DCM boundary.

True RMS, average and heating factor of a trapezoidal switched-current pulse, with rectangle and triangle as special cases - the conduction-loss workhorse.

Resonant frequency, characteristic impedance, Q, damping, bandwidth and ringing decay for series and parallel RLC - tanks, filters and snubbers.

Conductor-backed coplanar waveguide impedance and effective Dk from conformal mapping, for RF traces with side ground pours over a plane.

Edge-coupled differential microstrip impedance, with single-ended and common-mode impedance and the coupling factor made explicit.

Characteristic impedance, effective Dk and propagation delay of a microstrip trace from the Hammerstad-Jensen model, with copper thickness correction.

Minimum trace-to-trace spacing by IPC-2221B Table 6-1: internal layers, external uncoated below and above 3050 m, and conformally coated boards.

Current capacity, required width, resistance and voltage drop for a PCB trace from the IPC-2221 charts, for internal and external layers.

Symmetric stripline impedance from the exact conformal-mapping solution, with propagation delay and per-length L and C.

Minimum clearance and creepage to IEC 60664-1 from working voltage, pollution degree, material group and overvoltage category. Altitude corrected.

Convection coefficient for air blown along a flat surface, from Reynolds and Nusselt, with the laminar to turbulent transition handled explicitly.

Fin efficiency and thermal resistance of a straight rectangular fin array, showing where extra fin height stops buying anything.

Convection coefficient for a plate in still air from Rayleigh and Nusselt, for vertical and horizontal surfaces, instead of guessing a value.

Junction-to-ambient thermal resistance through a conduction path to a surface losing heat by convection and radiation in parallel.

Thermal resistance of a plated via array through a PCB, with the improvement over bare laminate and the effective through-plane conductivity.

Peak temperature rise under single and repetitive power pulses from a Foster thermal network, as datasheets publish Zth curves.

Skin depth, surface resistance and 99% penetration depth for any conductor, with the good-conductor validity check stated explicitly.

Single-layer air-core solenoid inductance from the exact current-sheet (Nagaoka) solution, with Wheeler shown alongside as a model-risk check.

DC and AC resistance of round wire including the exact skin-effect solution, temperature correction, current density, loss and voltage drop.

Unit converter restricted to electromagnetics and thermal engineering: flux density, field strength, resistivity, %IACS, thermal conductivity, AWG and more.

Coupling coefficient, mutual inductance and link efficiency of two flat spiral coils, including the loss from lateral misalignment.