Not a machinist but an electrician that works on agricultural irrigation systems. We work on several different brands of rotary phase converters and have one that a local shop makes that we are having issues with. Seems from reading through past blogs on here that we started to narrow down to a bad rotor. These phase converters are often in remote locations and controlled remotely so when we show up to work on one the generally look like a failed start board. But once in awhile after all components (start caps, multiple boards and contractor) still have failure to start. They just hum in a locked position. Finally we found that turning rotor 5 degrees Would make them start. We then tested the rotor according to our rewind shop and found high and low readings in the rotor. Roto wouldn’t start if we put it on a low reading but would on the high. So we’re guessing rotor is bad. The catch is the person who designed the rotophase has passed away and new shop owners seem to not have a lot of knowledge or unwillingness to share. When I approached them about a new rotor they had never heard of that and there best option was a total replacement. Which is great for me I’d gladly replace with two Arco’s but I don’t think customer is interested in that route yet. As best I can find they are a weg 324t frame size motor. Is there a common size rotor per frame size? Or are rotors different between brands. Can you buy a motor from grainger and cut the output shaft off? We are just at a loss with this outfit. We have 3 to 4 different customers with the same problem. These phase converters we most likely flooded in 2019 Missouri River flood. All were taken to rewind shop for rebearing and cleaning of windings. Included picture from grainger of same size and model of weg motor. Thanks for any info.