To automatically attain reduction in power consumption and vibration, in a motor drive for a load in which a load torque periodically changes.
A motor drive system includes a motor 1 for driving a load, having a periodically changing load torque, and a motor controller 3. The motor controller 3 calculates a torque current command value iδ*, from the difference between an estimated motor speed ωe and a motor speed command value ω*; extracts a variational component derived from the load torque from a position-speed estimating section 20, by using a torque current correction value generating section 30 and makes an adder 31 add the value, obtained by multiplying the extracted value by a coefficient K outputted from a torque gain control section 32 to the torque current command value iδ* as a δ-axis current correction value iδc. The motor controller 3 drives the motor 1, on the basis of the added torque current command value (iδ*+iδc).
Daisuke Nagano
Kentaro Fujii