Connecting a prime mover driven alternator to a circuit with an existing alternating current

Apparatus and method are provided, for connecting prime mover driven alternator to circuit that has an existing alternating current. Alternator is connected to circuit when minimum current flows to or from alternator. The actual current is measured by controller following connection and the value of this current is used to determine the optimal connection conditions when alternator is next connected. Alternator is disconnected by controller by running down prime mover, monitoring the current and stalling prime mover when the current flow is at a minimum.