Single-shunt current sensing for multi-phase motor

Patent metadata

Field	Value
Publication number	US-9966893-B2
Application number	US-201615218383-A
Country	US
Kind code	B2
Filing date	Jul 25, 2016
Priority date	Jun 11, 2014
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A motor controller for providing a three-phase alternating current (AC) signal to a three-phase motor. The motor controller uses current feedback from a single shunt to monitor or control the three phase AC signal. The motor controller may include a three-phase DC to AC power inverter, a single-shunt current sensor, and a processor. During individual duty cycles when two or more phase signals are too close to each other, the processor may shift one of the phase signals in time so that its leading or trailing edges are a predetermined conflict time away from each other. Then, the processor may sample current from the single-shunt current sensor to determine currents of two of the three phase signals and then calculate current of a remaining one of the three phase signals. Sample times may depend on pulse widths and shifting of the phase signals.

First claim

Having thus described various embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following:

1. A motor controller for a motor, the motor controller comprising:
a three-phase DC to AC power inverter configured to provide three pulse width modulated (PWM) phase signals to power the motor, wherein the phase signals have pulses of varying widths centered at identical points in each duty cycle, the pulses having leading edges and trailing edges;
a current sensor coupled in series with the inverter and configured to receive current from the three phase signals simultaneously; and
a processor configured to:
control pulse-width modulation of the three phase signals of the power inverter;
when a pulse width difference between simultaneously occurring pulses of at least two of the phase signals are less than a preselected minimum conflict time, shift at least one of the phase signals in time such that a difference between leading edges or trailing edges of the pulses are equal to the preselected minimum conflict time;
shift two of the phase signals in time cycle when leading or trailing edges of pulses for all three phase signals in any duty are less than the preselected minimum conflict time, wherein one of the phase signals is shifted a first direction in time and another one of the phase signals is shifted a second direction in time, wherein the second direction is opposite the first direction;
detect current from the current sensor at sample times a preselected delay time before the leading edge and before the trailing edge of one of the pulses; and
shift at least one of the sample times according to an amount or amounts by which the at least one of the phase signals are shifted.

2. The motor controller of claim 1 , the processor further configured to:
determine currents of a first one and second one of the three phase signals at the sample times; and
calculate a current of a third one of the three phase signals using the determined currents of the first and second ones of the three phase signals.

3. The motor controller of claim 1 , wherein the processor is further configured to determine or track which of the three PWM phase signals is ranked maximum, minimum, and middle in respect to pulse duration or pulse width for any single duty cycle.

4. The motor controller of claim 3 , wherein at least the middle one of the three phase signals is shifted.

5. The motor controller of claim 3 , wherein the sample times are the preselected delay time before the leading and trailing edges of the middle one of the three phase signals before or after the middle one of the three phase signals is shifted.

6. The motor controller of claim 1 , further comprising an AC to DC rectifier configured to convert alternating current from an AC power source into a substantially direct current and providing the direct current to the DC to AC power inverter.

7. A motor controller for a three-phase motor, the motor controller comprising:
a three-phase DC to AC power inverter configured to provide three separate pulse width modulated (PWM) phase signals to power the three-phase motor, wherein the phase signals have pulses of varying widths centered at identical points in each duty cycle, the pulses having leading edges and trailing edges;
a current sensor coupled in series with the inverter and configured to receive current from the three phase signals simultaneously; and
a processor configured to:
control pulse-width modulation of the three phase signals of the power inverter;
when a pulse width difference between simultaneously occurring pulses of at least two of the phase signals are less than a preselected minimum conflict time, shift at least one of the phase signals in time such that a difference between leading edges or trailing edges of the pulses are equal to the preselected minimum conflict time, wherein the preselected minimum conflict time is an amount of time less than half a shortest pulse width of the three phase signals;
shift two of the phase signals in time cycle when leading or trailing edges of pulses for all three phase signals in any duty are less than the preselected minimum conflict time, wherein one of the phase signals is shifted a first direction in time and another one of the phase signals is shifted a second direction in time, wherein the second direction is opposite the first direction;
detect current from the current sensor at sample times a preselected delay time before the leading edge and before the trailing edge of one of the pulses; and
shift at least one of the sample times according to an amount or amounts by which the at least one of the phase signals are shifted.

8. The motor controller of claim 7 , the processor further configured to:
determine currents of a first one and second one of the three phase signals at the sample times; and
calculate a current of a third one of the three phase signals using the determined currents of the first and second ones of the three phase signals.

9. The motor controller of claim 7 , wherein the processor is further configured to determine or track which of the three PWM phase signals is ranked maximum, minimum, and middle in respect to pulse duration or pulse width for any single duty cycle.

10. The motor controller of claim 9 , wherein at least the middle one of the three phase signals is shifted.

11. The motor controller of claim 9 , wherein the sample times are the preselected delay time before the leading and trailing edges of the middle one of the three phase signals before or after the middle one of the three phase signals is shifted.

12. The motor controller of claim 7 , further comprising an AC to DC rectifier configured to convert alternating current from an AC power source into a substantially direct current and providing the direct current to the DC to AC power inverter.

Assignees

• Nidec Motor Corp

Inventors

• Schock Christopher D
• Shahi Prakash B

Classifications

• H02P6/12

  Monitoring commutation; Providing indication of commutation failure · CPC title

• H02P27/08 Primary

  with pulse width modulation · CPC title