Estimating the efficiency of pulsed alternators

The term pulsed alternator is used to describe a type of rotating machine capable of providing short bursts of high current. Output power is intended to come from energy stored in the form of rotational inertia. This is done in a three-step process. The field coil on the rotor is charged using a process called bootstrapping. When the desired charge is reached, the circuit is switched to the load, and any magnetic energy left in the field coil is used to charge the flywheel. The efficiency of pulsed alternators, a very important design metric, is dependent on many geometric and material parameters, on the load, and on the type of input excitation. This paper shows the derivation of the steady-state efficiency of a pulsed alternator connected to a static load based on Park´s model of a machine. The steady-state efficiency is then compared with the instantaneous and net efficiency of a simple discharge.