Troubleshooting - Wolfspeed SpeedVal MOD-MB-3P-0900V-40A Series User Manual

Troubleshooting

Distorted current waveforms when performing double pulse tests (switching energy)
The power daughter cards are shipped ready for high-power testing. A bank of low-resistance surface mount
resistors provides a means to measure high continuous current with good accuracy. However, the shunt
resistors need to be replaced with a higher resistance value to provide accurate dynamic current waveforms for
switching energy testing. Refer to the power daughter card user guide for detailed instructions. Figure 53 shows
the waveforms with the power daughter card in its stock configuration, which has been optimized for high-
power testing. The fast switching speeds of SiC devices can create noise and ringing in the measurement circuit.
With low-resistance shunts, the signal-to-noise ratio is relatively low, so parasitics in the measurement circuit
significantly change the measured waveform causing excessive peaks and ringing.
Figure 54 shows the waveforms with the power daughter cards modified for double pulse measurements. The
current waveform is much cleaner, and the ringing is less pronounced, allowing for more accurate double pulse
measurements.
Figure 53: Power daughter card waveforms optimized for power testing
Figure 54: Power daughter card waveforms optimized for double pulse testing
No current waveform
Verify that the MMCX to BNC adapter is connected to the I
PRD-08611 REV. 1, June 2024
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MOD-MB-3P-0900V-40A SpeedVal™ Kit Three-Phase Motherboard User Guide
test point on the power daughter card.
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