Power Electronics Measurement: SiC, GaN, Double-Pulse, Motor Drives and Power Integrity

This page collects AXMEAS Signal's field notes and explainers on power electronics measurement: characterising SiC and GaN transistors, double-pulse testing, gate drivers, isolated and high-voltage probing, motor-drive and inverter power analysis, power integrity, and battery emulation. Most articles start from a real demo screen at PCIM Europe, Embedded World, electronica or EuMW and work through what the numbers mean and how they could mislead.

Recurring themes: why fast wide-bandgap edges make the probe and its common-mode rejection the limiting factor; why static and dynamic characterisation give different answers for the same MOSFET; why total and fundamental power factor differ on PWM-fed motors; and why a no-load efficiency figure is mostly noise.

Frequently asked questions

Why is measuring GaN switching harder than SiC?

GaN transistors switch in a few nanoseconds with very high dv/dt. The measurement needs bandwidth well above the edge rate, very low probe loading and high common-mode rejection at high frequency, otherwise ringing and common-mode error dominate the waveform. Optically isolated probes are often used on the high-side gate.

What does a double-pulse test measure?

It measures switching energies (Eon, Eoff), reverse recovery and switching times of a transistor at a defined current and voltage, without heating the device: the first pulse builds the inductor current, the second captures turn-on at that current.

Why is total power factor lower than fundamental power factor on a PWM motor drive?

The PWM voltage contains large harmonic components. Total PF includes them; fundamental PF describes only the 50/60 Hz or motor-frequency component. The motor itself is judged on the fundamental; harmonic power is mostly loss.

Why do high-voltage probes need a calibrator check?

Gain, overshoot and skew differ between probes and channels. A known step from a probe calibrator shows gain error and step response before you trust a power or switching-loss calculation.

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