The motor is a 3 HP, 240 VAC, 1 phase, TEFC motor made by WEG. It powered a two-stage centrifugal water pump. The pump/motor started making a loud racket … like gears grinding. Noise seemed to emanate from the motor rather than the pump. Externally nothing looked amiss.
Unfortunately, the design is that an extension of the motor output shaft is the pump shaft. The only way to get a thorough look inside the motor was to remove the pump from the shaft, which meant the pump had to be completely disassembled. This was done, and with a bit of study, the probable culprit emerged.
The centrifugal starting switch assembly spins freely on the motor shaft when it should be fixed to the shaft. Figure 1 shows the shaft and parts on it. The shaft in the pics turns the cooling fan; it is not the output shaft, which is at the other end of the rotor. Looking at the shaft starting on the left is a flattened area for fan attachment (fan has been removed). Next is the bearing assembly. Next is the centrifugal switch assembly, which I believe is in the position in which it is supposed to be fixed to the shaft. Next is an external retaining ring. Finally, there is the rotor. No loose parts or pieces of parts were found inside the housing.
I believe the metal ring of the centrifugal switch was force-fitted on the shaft, and the role of the retaining ring was to limit how far the centrifugal switch could be pushed on to the shaft during assembly. With time, thousands of starts and about 3000 hours total running time, the metal ring of the centrifugal switch started slipping. Now the whole assembly spins freely on the shaft, has a slight wobble, and can move back and forth on the shaft. See Figure 2. The motor still starts because the default still-condition is for the starting coil and capacitor to be engaged.
The loud racket is because there is some friction between the metal ring of the centrifugal switch. So, it spins as the shaft turns, but as it does, its flyweights hit the tabs on the retaining ring. See Figure 3. The tabs show evidence of such collisions. Because the centrifugal switch assembly can move back and forth along the shaft, it bounces between the bearing assembly and the retaining ring (ouch!).
If I could remove the bearing assembly, I could slide the centrifugal switch off the shaft. Then drill a couple of small holes in its back plate and wire it to the tab eyes of the retaining ring. The bearing assembly also appears to have been force fitted to the shaft. Even if I could remove it without damage, getting it secured in position again would be problematic. I don’t know of an adhesive that I would trust to secure the metal ring of the centrifugal switch assembly to the shaft. Any ideas?
Mike in California