A PN-busbar common system includes motor drive devices for a plurality of motors, each of which is supplied with power from a common PN-busbar, where the motor drive devices individually drive the corresponding motors. Each of the motor drive devices executes a regenerative control on a basis of a regenerative-control start voltage, and controls to stop the regenerative control on a basis of a regenerative-control stop voltage, and also individually calculates a regenerative load ratio to control to enable or disable the regenerative control on a basis of a result of a comparison between a calculated regenerative load ratio and a set regeneration-capable load ratio.