Flywheel-speed sensing for an emergency-power engine

A system and controller for providing emergency power to an electrical load when a usual source of power for the load has failed, includes an electrical dynamo, an engine of controllable speed connectable by clutch to drive by a fixed speed ratio the dynamo, a continuously spinning flywheel to provide power while the engine is coming up to speed and during transient loads thereafter, and a control system. The flywheel is also connected with the dynamo, through a variable-speed transmission. When the engine is driving the dynamo, the speed of the engine is controlled by a loop, which involves sensing the torque of the flywheel, comparing the flywheel's speed with a first reference, and adjusting the throttle according to the difference. Simultaneously, the speed ratio of the variable transmission is controlled by a second loop, which involves sensing the output frequency of the dynamo, comparing it with a second reference to get a difference signal, and adjusting the transmission's ratio in accordance with the difference signal. For short interruptions of the usual power source, the flywheel provides emergency power and the engine is not started.