The rotor in a synchronous machine is coupled magnetically to the grid (basically a spring-mass system where the spring is a rotary field); there is virtually n

The rotor in a synchronous machine is coupled magnetically to the grid (basically a spring-mass system where the spring is a rotary field); there is virtually no reaction time in this mechanism. (It should be noted that other motors, including asynchronous machines, contribute as well) AIUI the HPR has reaction times on the order of a few seconds.