Refer to the schematic, the NUP4201MR6 is used for clamping the motor phase or dc bus voltage sampling, its standoff voltage, peak pulse power, peak impulse current and clamping voltage is enough in this signal chain circuit. Please make sure the ground of oscilloscope is connected correctly and the impedance of probe is good, and there is no short between U/V/W and 3.3V/GND.
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