In an apparatus, a determiner determines whether a two-MG frequency ratio of a first electrical frequency of a first MG to a second electrical frequency of a second MG is within a specific frequency-ratio range. The specific frequency-ratio range includes 1/6n where n is an integer excluding zero. An update-cycle controller controls an update cycle of a command voltage according to the determined result such that the update cycle during a specific drive of the first MG is longer than the update cycle during a usual drive of the first MG while a cycle of a carrier signal is maintained during both the usual and specific drives. The specific drive represents drive of the first MG while the two-MG frequency ratio is within the specific frequency-ratio range. The usual drive represents drive of the first MG while the two-MG frequency ratio is out of the specific frequency-ratio range.