Quasi vector motor controller

Patent metadata

Field	Value
Publication number	US-9685898-B2
Application number	US-201414321356-A
Country	US
Kind code	B2
Filing date	Jul 1, 2014
Priority date	May 19, 2014
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

An apparatus includes a switch module that selectively turns on a switch to connect an input power conductor connected to a voltage source to a motor in a sequence. The switch for each phase is turned on for a portion of a cycle of a fundamental frequency of the voltage source. A source phase module determines a phase of the AC voltage source, a back-EMF phase module determines a phase of a back-EMF of the motor, and a torque module determines when a phase difference between the phase of the AC voltage source and the phase of the back-EMF is within a phase range indicative of a positive motor torque. A pulse module enables the switches in response to the phase difference having a phase within the phase range and disables the switches in response to the phase difference having a phase not in the phase range.

First claim

What is claimed is:

1. An apparatus comprising:
a switch module that, for each phase, selectively turns on a switch to connect an input power conductor connected to an alternating current (“AC”) voltage source to a motor in a sequence, wherein the switch for each phase is turned on for a portion of a cycle of a fundamental frequency of the AC voltage source, the portion comprising less than a full cycle of the fundamental frequency;
a source phase module that determines a phase of the AC voltage source;
a back-EMF phase module that determines a phase of a back-electromotive force (“back-EMF”) of the motor;
a torque module that determines when a phase difference between the phase of the AC voltage source and the phase of the back-EMF is within a phase range indicative of a positive motor torque; and
a pulse module that enables turning on of the switch for each phase of the motor in response to the phase difference comprising a phase within the phase range and disables turning on of the switch for each phase of the motor in response to the phase difference comprising a phase not in the phase range,
wherein at least a portion of the switch module, the source phase module, the back-EMF phase module, the torque module, and the pulse module comprise one or more of hardware and executable code, the executable code stored on one or more non-transitory computer readable storage media.

2. The apparatus of claim 1 , wherein the phase range comprises phases where motor torque is expected to be positive.

3. The apparatus of claim 2 , wherein the phase range comprises phases between about zero degrees and about 30 degrees.

4. The apparatus of claim 1 , wherein the source phase module determines a phase of the AC voltage source using the following equation:

θ
supply

=

tan

-
1

⁡

(

V
β

V
α

)

wherein
θ supply is the phase of the voltage source; and
V α , V β are stator voltage in a stationary reference frame,
wherein the voltage for each phase of the voltage source is transformed to the stationary reference frame using an alpha-beta transformation.

5. The apparatus of claim 1 , wherein the back-EMF phase module determines a phase of back-EMF of the motor using voltage and current measurements in a stator of the motor.

6. The apparatus of claim 1 , wherein the back-EMF phase module determines a phase of back-EMF of the motor using the following equation:

θ
emf

=

tan

-
1

(

∫

(

V
β

-

I
β

⁢

R
s

)

⁢

ⅆ
t

∫

(

V
α

-

I
α

⁢

R
s

)

⁢

ⅆ
t

)

+

90
⁢
°

wherein
θ emf is the phase of the back-EMF of the motor; and
R s is resistance of stator winding;
V α , V β are stator voltage in a stationary reference frame; and
I α , I β are stator current in the stationary reference frame,
where the voltage and current for each phase of the motor is transformed to the stationary reference frame using an alpha-beta transformation.

7. The apparatus of claim 1 , wherein the switch module comprises one or more thyristors for each phase of the motor and wherein each thyristor is controlled by adjusting a phase angle for turning on each thyristor.

8. The apparatus of claim 1 , further comprising a startup module that varies an on time of each switch to control motor startup, the on time for each switch comprising a time when the switch is in a conductive state.

9. The apparatus of claim 8 , wherein the startup module comprises a DFC module that sequentially applies a series of discrete frequencies to the motor as part of a discrete frequency control (“DFC”) method for motor starting, wherein each discrete frequency comprises a frequency lower than the fundamental frequency of the AC voltage source providing power to the motor.

10. The apparatus of claim 9 , wherein the DFC module applies a discrete frequency by varying a phase angle for turning on a thyristor to generate positive current pulses of varying amplitudes for a positive half cycle of the discrete frequency and then varying a phase angle for turning on a thyristor to generate negative current pulses of varying amplitudes for a negative half cycle of the discrete frequency, wherein each current pulse is generated at a rate consistent with the fundamental frequency of the AC voltage source.

11. The apparatus of claim 8 , wherein the startup module further comprises a step start module that applies one or more starting steps, wherein each starting step comprises maintaining on time of the switches at a fixed value for a predetermined period of time.

12. The apparatus of claim 8 , wherein the startup module comprises a ramp module that ramps on time o

Assignees

• Rockwell Automation Tech Inc

Inventors

• Wei Kun
• Lu Haihui
• Jaap Andrew
• Messersmith David
• Langer Randall
• Lee Ping

Classifications

• H02P1/04

  Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter · CPC title

• H02P27/047 Primary

  V/F converter, wherein the voltage is controlled proportionally with the frequency · CPC title

• H02P1/26

  for starting an individual polyphase induction motor · CPC title

• H02P1/16

  for starting dynamo-electric motors or dynamo-electric converters · CPC title

• H02P21/28 Primary

  Stator flux based control · CPC title