Motor control apparatus and method for controlling motor

• US 9,641,120 B2
• Filed: 10/22/2014
• Issued: 05/02/2017
• Est. Priority Date: 10/31/2013
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: Iura, Hideaki, Matsuda, Shuji
• Primary Examiner(s): Santana, Eduardo Colon
• Assistant Examiner(s): JOSEPH, DEVON A
• Application Number:
  US14/520,393
• Publication Number:
  US 20150115864A1
• Time in Patent Office: 923 Days
• Field of Search: 318808
• CPC Class Codes: H02P 1/029 Restarting, e.g. after power failure
• CPC Class Codes: H02P 1/28 by progressive increase of voltage applied to primary circuit of motor
• CPC Class Codes: H02P 1/30 by progressive increase of frequency of supply to primary circuit of motor
• CPC Class Codes: H02P 23/28 Controlling the motor by varying the switching frequency of switches connected to a DC supply and the motor phases
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

A motor control apparatus includes a voltage regulator to execute a voltage increase mode to increase a voltage applied to an induction motor from a lower limit of a first range over time. A frequency regulator executes a frequency decrease mode to decrease a frequency of the voltage from an upper limit of a second range over time. When a current through the motor exceeds a first threshold in the voltage increase mode, a mode changer changes the mode to the frequency decrease mode. When the current through the motor becomes smaller than a second threshold in the frequency decrease mode, the mode changer changes the mode to the voltage increase mode to control the motor to change from a free running state to a state in which the voltage and the frequency satisfy a relationship. A determinator determines whether the voltage and the frequency satisfy the relationship.

Claims

1. A motor control apparatus comprising:

a voltage regulator configured to execute a voltage increase mode to increase a voltage applied to an induction motor from a lower limit of a first predetermined range over time;

a frequency regulator configured to execute a frequency decrease mode to decrease a frequency of the applied voltage from an upper limit of a second predetermined range over time;

a mode changer configured to change the voltage increase mode to the frequency decrease mode in response to a determination that a current flowing through the induction motor exceeds a first current threshold in the voltage increase mode, and configured to change the frequency decrease mode to the voltage increase mode in response to a determination that the current flowing through the induction motor becomes smaller than a second current threshold that is smaller than the first current threshold in the frequency decrease mode, so as to control the induction motor to change from a free running state to a state in which the applied voltage and the frequency satisfy a predetermined relationship; and

a determinator configured to determine whether the applied voltage and the frequency satisfy the predetermined relationship.

2. The motor control apparatus according to claim 1, wherein when the applied voltage and the frequency satisfy the predetermined relationship in the voltage increase mode, the determinator is configured to change a control mode of the induction motor to V/f control.

3. The motor control apparatus according to claim 1, wherein when the applied voltage and the frequency satisfy the predetermined relationship in the frequency decrease mode, and when the current flowing through the induction motor becomes smaller than a third threshold that is smaller than the first current threshold in a predetermined period of time, the determinator is configured to change a control mode of the induction motor to V/f control.

4. The motor control apparatus according to claim 3,

wherein when the current flowing through the induction motor does not become smaller than the third threshold in the predetermined period of time, the voltage regulator and the frequency regulator are configured to execute a double decrease mode to respectively decrease the applied voltage and the frequency over time,

wherein when the current flowing through the induction motor becomes smaller than a fourth threshold that is smaller than the first current threshold in the double decrease mode, the determinator is configured to change the control mode of the induction motor to the V/f control.

5. The motor control apparatus according to claim 4, wherein when the current flowing through the induction motor does not become smaller than the fourth threshold that is smaller than the first current threshold in the double decrease mode, and when the frequency reaches a lower limit of the second predetermined range in the double decrease mode, the determinator is configured to change the control mode of the induction motor to the V/f control.

8. The motor control apparatus according to claim 1, wherein the determinator determines whether the applied voltage and the frequency satisfy the predetermined relationship by comparing relative magnitudes of the applied voltage and the frequency.

9. The motor control apparatus according to claim 1, wherein the voltage regulator increases the voltage applied to the induction motor while the frequency of the applied voltage is held constant.

10. The motor control apparatus according to claim 1, wherein the frequency regulator decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.

17. The motor control apparatus according to claim 9, wherein the frequency regulator decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.

20. The motor control apparatus according to claim 1, wherein the mode changer is configured to compare the current flowing through the induction motor with each of the first current threshold and the second current threshold to perform the determination that the current flowing through the induction motor exceeds the first current threshold and the determination that the current flowing through the induction motor becomes smaller than the second current threshold.

6. A method for controlling a motor, the method comprising:

executing a voltage increase mode by a voltage regulator to increase a voltage applied to an induction motor from a lower limit of a predetermined range over time;

executing a frequency decrease mode by a frequency regulator to decrease a frequency of the applied voltage from an upper limit of a predetermined range over time;

changing the voltage increase mode to the frequency decrease mode in response to a determination that a current flowing through the induction motor exceeds a first current threshold in the voltage increase mode;

changing the frequency decrease mode to the voltage increase mode in response to a determination that the current flowing through the induction motor becomes smaller than a second current threshold that is smaller than the first current threshold in the frequency decrease mode to change from a free running state to a state in which the applied voltage and the frequency satisfy a predetermined relationship; and

determining whether the applied voltage and the frequency satisfy the predetermined relationship.

11. The method for controlling a motor according to claim 6, wherein the determining whether the applied voltage and the frequency satisfy the predetermined relationship is performed by comparing relative magnitudes of the applied voltage and the frequency.

12. The method for controlling a motor according to claim 6, wherein the executing the voltage increase mode increases the voltage applied to the induction motor while the frequency of the applied voltage is held constant.

13. The method for controlling a motor according to claim 6, wherein the executing the frequency decrease mode decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.

18. The method for controlling a motor according to claim 12, wherein the executing the frequency decrease mode decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.

7. A motor control apparatus comprising:

a voltage regulator configured to execute a voltage increase mode to increase a voltage applied to an induction motor from a lower limit of a first predetermined range over time;

a frequency regulator configured to execute a frequency decrease mode to decrease a frequency of the applied voltage from an upper limit of a second predetermined range over time;

mode changing means for changing the voltage increase mode to the frequency decrease mode in response to a determination that a current flowing through the induction motor exceeds a first current threshold in the voltage increase mode, and for changing the frequency decrease mode to the voltage increase mode in response to a determination that the current flowing through the induction motor becomes smaller than a second current threshold that is smaller than the first current threshold in the frequency decrease mode, so as to control the induction motor to change from a free running state to a state in which the applied voltage and the frequency satisfy a predetermined relationship; and

a determinator configured to determine whether the applied voltage and the frequency satisfy the predetermined relationship.

14. The motor control apparatus according to claim 7, wherein the determinator determines whether the applied voltage and the frequency satisfy the predetermined relationship by comparing relative magnitudes of the applied voltage and the frequency.

15. The motor control apparatus according to claim 7, wherein the voltage regulator increases the voltage applied to the induction motor while the frequency of the applied voltage is held constant.

16. The motor control apparatus according to claim 7, wherein the frequency regulator decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.

19. The motor control apparatus according to claim 15, wherein the frequency regulator decreases the frequency of the applied voltage while the voltage applied to the induction motor is held constant.