Motor control device

A motor controller for controlling an operation of a plurality of motors, the motor controller comprising:

• a plurality of inverters, each of the plurality of inverters including a switching element to supply power to a corresponding motor of the plurality of motors through pulse width modulation control based on a carrier signal;
• a direct current power supply configured to supply power to the plurality of inverters;
• and
• a capacitor connected parallel to the direct current power supply,
• wherein each of the plurality of inverters is assigned with a reference frequency based on a switching frequency of the inverter, and the reference frequency is associated with the carrier signal for the pulse width modulation control,
• each of the plurality of inverters is categorized into one of a plurality of groups based on the reference frequency assigned to the inverter, and
• all inverters in each of the plurality of groups have corresponding carrier signals being triangular wave signals determined based on the reference frequency assigned to the group, and at least one of the carrier signals corresponding to all the inverters in each of the plurality of groups has a frequency different from a frequency of another carrier signal of the carrier signals, wherein
• carrier signals in each of the plurality of groups have a frequency variation smaller than a difference in the reference frequency between the group and a group with a reference frequency closest to a reference frequency of the group, and
• a group with a lower reference frequency of two groups has a highest frequency of carrier signals lower than a lowest frequency of carrier signals for a group with a higher reference frequency of the two groups.