Ordinary gensets utilize diesel or gasoline combustion engines that are controlled to run at a fixed speed so that the directly coupled alternator driven by the engine produces voltage with a fixed frequency of either 50 or 60 Hz.
Switched Reluctance Generators (SRG) running the engine at variable speed and using power electronics to convert a variable rotation frequency of the prime mover to a fixed voltage and frequency allows for a more efficient operation of the genset. With advanced gasoline or diesel engines and variable speed technology it is possible to reduce weight by 30-60% or even more thanks to liquid cooling and increase fuel efficiency by up to 30-40% by adjusting the speed of the engine depending of the load. The speed of the engine is controlled via a user interface which allows the engine to run at it most efficient operating point for a given load and ambient thermal conditions. It is also possible to have the engine run where it is most audibly quiet, or at its least-polluting operating point. DC power capacitors of the SR generator make the genset less sensitive to load transients and increase the output voltage stability.
A block diagram of the electronic power conversion system for a genset featuring a switched reluctance starter-generator is shown above. The variable frequency pulses produced by the switched reluctance generator via diodes of excitation system charge capacitor C which stabilizes the output DC voltage and an inverter is used to produce controllable AC voltage with selectable frequency. Bidirectional back/boost converter charges the battery in operating mode and converts the battery voltage during the starting mode.