Combination static/dynamic inverter

Abstract

A power converter provides an AC output selectively using power from either a battery source or an alternator. The power converter includes a static converter (100) that is connected to receive DC from a battery (30), converting the DC to a relatively high frequency AC using a pulse width modulator (200). The high frequency AC is transformed to a higher voltage AC that is rectified and is used to charge a capacitor bank (104). The DC on the capacitor bank is converted to 120 (or 240) volts AC at 50/60 Hz by an inverter comprising an inverter (106) to provide power for an AC load. As the requirement for power by the AC load increases above a predefined level, a dynamic converter (24a) is energized to supply power to charge the capacitor bank in place of the static converter. The dynamic converter draws its power from a three-phase alternator (12) that includes three-phase AC output terminals connected to three-phase primary windings (140) of a transformer having a plurality of secondary windings. Secondary windings (168) produce a substantially higher voltage than the voltage from the alternator, and their output signal is rectified to charge the capacitor bank. The battery is charged with current supplied (after rectification) by secondary windings (148). Rectified DC supplied from the output of secondary windings (146) is supplied to the field winding of the alternator and controlled in response to the voltage developed across the battery terminals by rectified signal output from secondary windings (148). As the AC load draws power from the capacitor bank (through the H-bridge), the voltage of the battery charging current supplied by secondary windings (148) drops, causing a voltage regulator circuit (34) to increase the field winding current, and thereby increasing the power supplied by the alternator to compensate the greater load.