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Power module thermal sizing tool

IGBT Loss & Junction Temperature Calculator

Estimate IGBT and freewheeling-diode conduction/switching losses from datasheet parameters, then check steady-state junction temperatures and the cooling resistance required from a cold plate, heat pipe module or skived heat sink.

2-LEVEL PWM · STEADY STATE

1Operating pointCurrent, voltage and PWM

2Datasheet valuesOn-state curves and energies

3Thermal pathJunction, interface and cooler

4Selection resultTemperature and cooling margin

1 · Inverter operating point

Values for one cooled assembly

Power-stage topology

Phase current RMS

A RMS

Sinusoidal peak current is calculated as √2 × RMS.

DC-link voltage

Switching frequency

kHz

Modulation index

Load power factor cos φUse the signed displacement power factor.

2 · Datasheet loss parameters

Prefer curves at the intended junction temperature

IGBT IGBT chip position

VCE0 intercept

On-state slope rCE

mΩ

Turn-on energy Eon

Turn-off energy Eoff

IGBT RθJC

°C/W

FWD Freewheeling diode position

VF0 intercept

On-state slope rF

mΩ

Reverse-recovery energy Erec

FWD RθJC

°C/W

Switching-energy reference and correction

Datasheet test voltage

Datasheet test current

Energy correction factor

For gate resistance, temperature and tolerance.

Current scaling exponentUse 1.0 if only one datasheet test point is known.

3 · Thermal path and cooling candidate

Steady-state screening

Coolant inlet temperature

°C

Candidate cold plate Rθ

°C/W

Module-to-cooler interface Rθ

°C/W

Equivalent common resistance based on total assembly loss.

Maximum design junction temperature

°C

Thermal design load margin

Cold plate check: Use inlet coolant temperature and a cold-plate base-to-coolant thermal resistance at the intended flow. Pressure drop and coolant outlet rise must be checked separately.

Cooling selection result

Three-phase 6-pack · Cold Plate

Candidate passes

Total semiconductor loss—Entire cooled assembly

Required heat rejection—Includes entered thermal design margin

Estimated maximum junction—Hottest chip type

Maximum allowable cooler Rθ—From cooler base to reference fluid/air

—

Loss distribution for the complete assembly— W

IGBT conduction —IGBT switching —FWD conduction —FWD recovery —

Steady-state thermal path—°C margin

Reference

—

Cooler base

—

Module case

—

IGBT junction

—

FWD junction

—

Peak phase current—

Loss per IGBT/FWD position—

Cooler Rθ margin—

Max cooler-base temperature—

IGBT loss per position—

FWD loss per position—

Cold Plate: this result evaluates thermal resistance only. Confirm coolant type, inlet temperature, flow, outlet temperature, internal pressure drop, pump curve and mounting flatness before final sizing.

Screening boundary: use datasheet curves at the intended junction temperature and gate resistance. The model assumes sinusoidal current, two-level PWM, linear voltage scaling and adjustable current scaling of switching energies. It does not replace manufacturer loss simulation, transient Zth analysis, current ripple, dead-time analysis, chip-to-chip coupling or prototype temperature measurement.