In a system according to an embodiment, a rotating electrical machine is a permanent magnet type configured by forming magnetic poles of a rotor using permanent magnets. An inverter generates an AC voltage by switching and outputs the voltage to the rotating electrical machine as driving power. A control device detects a field component current in the rotating electrical machine, estimates a rotorspeed of the rotating electrical machine from the detected current, determines a field component voltage in the rotating electrical machine on the basis of a difference between the estimated rotor speed and a target speed, and controls switching of the inverter on the basis of the field component voltage to cause the rotor speed to follow the target speed. The permanent magnets are R-Co based magnets (R is at least one element selected from rare earth elements) containing 25 to 40 atomic% iron. Further, on the basis of a negative field component current characteristic corresponding to the rotor speed and based on the material of the permanent magnet, the control device increases or decreases the field component voltage, thereby performing field weakening control.