how many agree that stator failure is caused by vibration ?

[Ken Williams]

Referring back several weeks to the discussion of rectifier operation, when the battery is below the charge voltage, roughly 14 volts, the alternator output current flows through the 3 supply diodes, into the battery/loads and back to the stator through the 3 return diodes.  When the battery is above the charge voltage, perhaps from being jumped by a running automobile, the output flows through the SCRs and back to the stator through the 3 return diodes.  During usual operation, stator phase current flows through the supply diode until the SCR is triggered.  Then the remainder of the current for that cycle flows through the SCR. 

My best guess is that the most power is dissipated in the rectifier during normal operation.  This is because the SCRs switch when phase currents are high.