Hello ,
Thanks for contacting NXP Tech Support. I am here to support you.
[Q1] Is it possible to use PowerQuad DSP Coprocessor for motor current signature analysis - FFT based ?
[A1] Yes, it is possible.
[Q2] Any example of phase current FFT effectivnes with PowerQuad on 3 phase currents?
[A2] The frdmmcxn947_powerquad_benchmark_fft demo could be a useful reference for your questions. By converting and inputting your three-phase current data into an appropriate format, it may meet your needs.
To get the demo, download the FRDM-MCXN947 SDK. Refer to Importing an SDK Package into MCUXpresso IDE and install it in MCUXpresso. Open it as below picture shows.

Hope the above information is helpful to you.
BR,
Celeste