Thank you jamesbolt,
Welcome to the DigiKey forum.
Three phase is such a rich topic. I was once in a commercial building that lost one leg. The service technicians were not happy as several of the HVAC motors did not survive.
In another application, I worked on a 7.5 hp two-speed fan that was constantly throwing belts. As we troubleshot, we found that the motor was spinning CW for low speed and CCW for high speed. That certainly explains the squeal and belt issues. A two-wire swap of the high-speed motor connections and we never had a problem again.
Sincerely,
Aaron