Reluctance synchronous machines (RSMs) and drives include a multitude of machine topologies in terms of rotor, stator windings, and stator current control. Line-start (constant speed) and inverter-fed (variable speed) applications are easily achieved in a power range from a few hundred watts to megawatts. RSMs offer strong competition to existing variable speed brushless drives for applications from computer peripherals through robotics to electric traction for rail transport. This book explores fully the possible topologies, their characteristics, and applications.