Electric motor control device

Ripple current flowing into a main circuit capacitor (4) is estimated based on power output to an electric motor (9) and a system impedance (2), thereby making it possible to always perform the ripple current estimation and life estimation calculation of the main circuit capacitor (4) in an online manner. Since the data (Zs) of the system impedance (2) significantly affecting the ripple current estimation of the main circuit capacitor (4) is used, it is possible to estimate capacitor ripple current in accordance with the magnitude of the system impedance (2), enabling main circuit capacitor life estimation calculation with high accuracy.