Patent ID: 7425806

Claim:
A method of controlling a variable speed drive having a converter stage, a DC link stage, and an inverter stage, the method comprising: providing an inverter stage having a plurality of inverters electrically connected in parallel to a DC link stage, each inverter of the plurality of inverters being configured to power a corresponding load; generating a switching signal for each inverter of the plurality of inverters with a plurality of modulators, the switching signal being operable to activate and deactivate the inverter to obtain a preselected output power and a preselected output frequency from the inverter, wherein generating a switching signal comprises: providing a common input signal to the plurality of modulators; and providing a phase shifted or time shifted input signal to each modulator of the plurality of modulators, wherein the phase shifted or time shifted input signal for one of the modulators being shifted relative to the corresponding input signal provided to the other modulators; and interleaving the switching signals for each inverter of the plurality of inverters to reduce RMS ripple current at the DC link stage.