Hi all, first post on here. I'm an ex-heating engineer studying marine engineering at the moment and are currently covering 3 phase synchronous motors in class. I know from my past experiences that in single phase synchronous motor ( most oftern 3 way valves in domestic heating systems) they use a DC signal to stall the ball in a mid position, using microswitches to alternate between AC and DC using two resistors and a diode. My question is, does anyone know of an application of this DC stalling within a larger 3 phase motor? For my own curiosity more than anything else!