Rotary electric system with neutral-point powering system
In a rotary electric system, a controller works to turn high-side and low-side switching elements of first and second multiphase inverters on and off to thereby cause: the first multiphase inverter to intermittently supply a first phase current to the first star-connected multiphase stator windings per phase to charge first electromagnetic energy in first star-connected multiphase stator windings per phase, the first electromagnetic energy charging a capacitor; the second multiphase inverter to intermittently supply a second phase current to the second star-connected multiphase stator windings per phase to charge second electromagnetic energy in the second star-connected multiphase stator windings per phase, the second electromagnetic energy charging the capacitor. The first phase current for each phase and the second phase current for a corresponding one phase have a predetermined second phase difference from each other, and the first phase difference is matched with the second phase difference.
1. A rotary electric system comprising:
a rotary electric machine provided with a rotor, a common stator core, and a pair of first and second star-connected multiphase stator windings each with a neutral point, the neutral point of the first star-connected multiphase stator windings and the neutral point of the second star-connected multiphase stator windings having a same potential, the first and second star-connected multiphase stator windings being wound in the common stator core with a predetermined first phase difference therebetween, the rotary electric machine configured to rotate the rotor when at least one of the first and second star-connected multiphase stator windings is energized;
a pair of first and second multiphase inverters each having a high-side terminal and a common low-side terminal, the first multiphase inverter including a high-side switching element and a low-side switching element per phase of the first multiphase stator windings, the second multiphase inverter including a high-side switching element and a low-side switching element per phase of the second multiphase stator windings;
a capacitor connected between the high-side terminal and the low-side terminal of each of the first and second multiphase inverters;
a direct current power source connected between at least one of the high-side terminal and the low-side terminal of each of the first and second multiphase inverters and the neutral points of the first and second multiphase stator windings; and
a controller connected with the high-side and low-side switching elements per phase of each of the first and second multiphase stator windings and configured to turn the high-side and low-side switching elements on and off to thereby cause:
the first multiphase inverter to intermittently supply a first phase current to the first star-connected multiphase stator windings per phase to charge first electromagnetic energy in the first star-connected multiphase stator windings per phase, the first electromagnetic energy charging the capacitor;
the second multiphase inverter to intermittently supply a second phase current to the second star-connected multiphase stator windings per phase to charge second electromagnetic energy in the second star-connected multiphase stator windings per phase, the second electromagnetic energy charging the capacitor, the first phase current for each phase and the second phase current for a corresponding one phase having a predetermined second phase difference from each other, the first phase difference being matched with the second phase difference.
2. A rotary electric system according to claim 1 , further comprising:
a common conductive member having one and an other one end, the one end being connected with the direct current power source;
a first branch conductive member connecting between the neutral point of the first star-connected multiphase stator windings and the other one end of the common conductive member; and
a second branch conductive member connecting between the neutral point of the second star-connected multiphase stator windings and the other one end of the common conductive member.
3. A rotary electric system according to claim 1 , wherein the first phase difference is 60 electric degrees of rotation of the rotor.
4. A rotary electric system according to claim 1 , wherein the direct current power source has a high-side electrode and a low-side electrode, the high-side electrode of the direct current power source being connected with the neutral points of the first and second star-connected multiphase stator windings, the low-side electrode of the direct current power source being connected with the low-side terminal of each of the first and second multiphase inverters,
the first multiphase inverter is configured to supply an alternating current to each phase winding of the first star-connected multiphase stator windings based on a command current value for each phase winding thereof, the command current value varying in the form of a negatively offset sinusoidal wave as a position of the rotor is changed, and
the second multiphase inverter is configured to supply an alternating current to each phase winding of the second star-connected multiphase stator windings based on a command current value for each phase winding thereof, the command current value varying in the form of a negatively offset sinusoidal wave as a position of the rotor is changed.
5. A rotary electric system according to claim 1 , wherein the direct current power source has a high-side electrode and a low-side electrode, the high-side electrode of the direct current power source being connected with the high-side terminal of each the first and second multiphase inverters, the low-side electrode of the direct current power source being connected with the neutral points of the first and second star-connected multiphase stator windings,
the first multiphase inverter is configured to supply an alternating current to each phase winding of the first star-connected multiphase stator windings based on a command current value for each phase winding thereof, the command current value varying in the form of a positively offset sinusoidal wave as a position of the rotor is changed, and
the second multiphase inverter is configured to supply an alternating current to each phase winding of the second star-connected multiphase stator windings based on a command current value for each phase winding thereof, the command current value varying in the form of a positively offset sinusoidal wave as a position of the rotor is changed.
6. A rotary electric machine according to claim 1 , wherein the controller is configured to:
generate, based on a first PWM carrier signal, a first pulse signal with an adjustably modulated duty cycle;
supply the generated first pulse signal to each of the high-side and low-side switching elements per phase of the first multiphase inverter to thereby individually turn each of the high-side and low-side switching elements per phase of the first multiphase inverter on and off;
generate, based on a second PWM carrier signal, a second pulse signal with an adjustably modulated duty cycle; and
supply the generated second pulse signal to each of the high-side and low-side switching elements per phase of the second multiphase inverter to thereby individually turn each of the high-side and low-side switching elements per phase of the second multiphase inverter on and off, the first PWM carrier signal being matched in frequency with the second PWM carrier signal and reversed in phase from the second PWM carrier signal.
7. A rotary electric system according to claim 1 , wherein the rotary electric machine is installed in a power steering system as a drive motor for increasing steering force to be applied to a steering.
8. A rotary electric system according to claim 1 , wherein the rotary electric machine is installed in an air-conditioner for a motor vehicle as a drive motor for driving a compressor of the air-conditioner.