INVERTER CONTROLLER AND VEHICLE ON-BOARD FLUID MACHINE

An inverter controller is used to control an inverter circuit, which drives a vehicle on-board electric motor using a vehicle on-board electricity storage device. A rotation controlling unit of the inverter controller executes a process that derives two-phase voltage command values based on an external command value delivered from an external device and an actual rotation speed, and a process that derives three-phase voltage command values based on the two-phase voltage command values. In a case in which a voltage utilization factor is less than or equal to a utilization factor threshold, the rotation controlling unit derives, by switching at a switching period, sets of three-phase voltage command values of which the line voltages of the vehicle on-board electric motor are the same and the variation ranges are different.