A system and method for controlling a DC midpoint terminal voltage of a three level inverter is provided. The method includes receiving an input power signal at a three level motor control system that includes a three level inverter, the three level inverter powering an electric motor, determining, in the three level motor control system, a speed value of the electric motor, and adjusting a zero-sequence inverter output voltage to adjust a midpoint voltage at the DC midpoint based on the determined speed value.

A system and method for controlling a DC midpoint terminal voltage of a three level inverter is provided. The method includes receiving an input power signal at a three level motor control system that includes a three level inverter, the three level inverter powering an electric motor, determining, in the three level motor control system, a speed value of the electric motor, and adjusting a zero-sequence inverter output voltage to adjust a midpoint voltage at the DC midpoint based on the determined speed value.

In an inverter module (10) including a plurality of switching elements (11), a positive-polarity bus bar (14), a negative-polarity bus bar (15), and a plurality of output bus bars (16, 17, and 18), the plurality of output bus bars (16, 17, and 18) are disposed in a first direction (D1) in which upper-stage-side switching elements (11U) and lower-stage-side switching elements (11L) are placed side by side, and the positive-polarity bus bar (14) and the negative-polarity bus bar (15) are disposed in a second direction (D2) intersecting the first direction (D1).

In an inverter module (10) including a plurality of switching elements (11), a positive-polarity bus bar (14), a negative-polarity bus bar (15), and a plurality of output bus bars (16, 17, and 18), the plurality of output bus bars (16, 17, and 18) are disposed in a first direction (D1) in which upper-stage-side switching elements (11U) and lower-stage-side switching elements (11L) are placed side by side, and the positive-polarity bus bar (14) and the negative-polarity bus bar (15) are disposed in a second direction (D2) intersecting the first direction (D1).

Provided is a snubber circuit comprising N parallel charging paths each having a positive-side capacitor, a first diode, and a negative-side capacitor sequentially connected in series between a positive-side terminal and a negative-side terminal, and configured to conduct current from the positive-side terminal toward the negative-side terminal; (N+1) parallel discharging paths each having a second diode connected between the negative-side terminal or the negative-side capacitor of k.sup.th charging path of N charging paths and the positive-side capacitor of (k+1).sup.th charging path of N charging paths or the positive-side terminal, and configured to counduct current from the negative-side terminal toward the positive-side terminal via at least one of the negative-side capacitor and the positive-side capacitor; and at least one auxiliary capacitor each being connected in parallel to at least one of the N first diodes included on N charging paths and (N+1) second diodes included on (N+1) discharging paths.

Provided is a snubber circuit comprising N parallel charging paths each having a positive-side capacitor, a first diode, and a negative-side capacitor sequentially connected in series between a positive-side terminal and a negative-side terminal, and configured to conduct current from the positive-side terminal toward the negative-side terminal; (N+1) parallel discharging paths each having a second diode connected between the negative-side terminal or the negative-side capacitor of k.sup.th charging path of N charging paths and the positive-side capacitor of (k+1).sup.th charging path of N charging paths or the positive-side terminal, and configured to counduct current from the negative-side terminal toward the positive-side terminal via at least one of the negative-side capacitor and the positive-side capacitor; and at least one auxiliary capacitor each being connected in parallel to at least one of the N first diodes included on N charging paths and (N+1) second diodes included on (N+1) discharging paths.

A rotary anode driving device includes a DC power supply, an inverter circuit which is connected to the DC power supply and includes a plurality of switching elements and, the inverter circuit generates an AC voltage from a DC voltage of the DC power supply, and outputs the AC voltage to a stator coil which generates a rotating magnetic field of an X-ray tube; a pulse width modulation (PWM) waveform generator configured to generate an AC voltage of two phases or three phases as the AC voltage from the DC voltage by performing PWM control of the switching elements of the inverter circuit; and a capacitor connected in series to an input side of a stator coil of at least one phase of the stator coil, the capacitor having an electrostatic capacitance constituting a series resonant circuit with the stator coil to which the capacitor is connected.

A rotary anode driving device includes a DC power supply, an inverter circuit which is connected to the DC power supply and includes a plurality of switching elements and, the inverter circuit generates an AC voltage from a DC voltage of the DC power supply, and outputs the AC voltage to a stator coil which generates a rotating magnetic field of an X-ray tube; a pulse width modulation (PWM) waveform generator configured to generate an AC voltage of two phases or three phases as the AC voltage from the DC voltage by performing PWM control of the switching elements of the inverter circuit; and a capacitor connected in series to an input side of a stator coil of at least one phase of the stator coil, the capacitor having an electrostatic capacitance constituting a series resonant circuit with the stator coil to which the capacitor is connected.

A robot includes a motor driven by a three-phase alternating current, an AC conversion section configured to convert a direct current into a three-phase alternating current and output the three-phase alternating current to the motor, a first detecting section configured to detect a current value of the direct current before being input to the AC conversion section, a second detecting section configured to detect a current value of the direct current before being input to the AC conversion section or the three-phase alternating current output by the AC conversion section, a power-supply adjusting section configured to adjust power supply to the motor, and a control section configured to control operation of the power-supply adjusting section based on at least one of a detection result of the first detecting section and a detection result of the second detecting section.

A robot includes a motor driven by a three-phase alternating current, an AC conversion section configured to convert a direct current into a three-phase alternating current and output the three-phase alternating current to the motor, a first detecting section configured to detect a current value of the direct current before being input to the AC conversion section, a second detecting section configured to detect a current value of the direct current before being input to the AC conversion section or the three-phase alternating current output by the AC conversion section, a power-supply adjusting section configured to adjust power supply to the motor, and a control section configured to control operation of the power-supply adjusting section based on at least one of a detection result of the first detecting section and a detection result of the second detecting section.