Motor driving apparatus

• US 7,868,569 B2
• Filed: 12/23/2008
• Issued: 01/11/2011
• Est. Priority Date: 02/28/2008
• Status: Active Grant

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Yamada, Yuuichi, Yaeshima, Mamoru, Iwashita, Yasusuke, Sakai, Koujirou, Shirouzu, Masatomo
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US12/342,711
• Publication Number:
  US 20090218976A1
• Time in Patent Office: 749 Days
• Field of Search: 318/801, 318/802, 318/803, 318/806, 318/798, 318/139, 318/440, 318/376, 318/722, 320/135, 320/127, 320/146, 320/132, 320/136, 320/137, 320/166, 320/107
• US Class Current: 318/376
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements

Abstract

A motor driving apparatus comprises a charge/discharge control circuit for controlling charge to or discharge from a capacitor connected in parallel in a link section between a converter and an inverter, and a current control means for controlling discharge current from the charge/discharge control circuit. The current control means controls discharge current from the charge/discharge control circuit based on input current to the inverter or output current from the converter so that output current from the converter is equal to a prescribed value.

Claims

1. A motor driving apparatus which comprises a converter for converting an AC voltage from an AC power source into a DC voltage, an inverter for converting the converted DC voltage back into an AC voltage, a capacitor connected in parallel in a link section between the converter and the inverter, and a charge/discharge control circuit for controlling charge to and discharge from the capacitor, wherein

a smoothing capacitor is connected between the converter and the inverter, and the capacitor connected in parallel in the link section is connected in parallel with the smoothing capacitor via the charge/discharge control circuit, and wherein

said motor driving apparatus further comprises a current control means for controlling discharge current from the charge/discharge control circuit based on at least one of the following values (1) to (5) so that input/output current or input/output power of the converter is equal to a prescribed value:

(1) input current or input power to the inverter;

(2) output power from the inverter;

(3) motor output power;

(4) input current or input power to the converter; and

(5) output current or output power from the converter.

2. The motor driving apparatus according to claim 1, wherein said current control means controls discharge current from the charge/discharge control circuit only when at least one of the value (1) to (5) exceeds the prescribed value of the input/output current or power of the converter.

3. The motor driving apparatus according to claim 1, further comprising a command value calculation means for calculating a difference between at least one of said value (1) to (3) and the prescribed value as a command value, wherein said current control means controls discharge current from the charge/discharge control circuit so that the value of the discharge current is equal to the command value calculated by the command value calculation means.

4. The motor driving apparatus according to claim 3, wherein the current control means has a hysteresis comparator receiving said command value and the amount of current flowing through the charge/discharge control circuit and controls discharge current from the charge/discharge control circuit based on an output signal from the hysteresis comparator.

5. The motor driving apparatus according to claim 3, wherein the current control means controls discharge current from the charge/discharge control circuit using the command value and a PWM command generated through current control based on the amount of current flowing through the charge/discharge control circuit so that the amount of current flowing through the charge/discharge control circuit is equal to said command value.

6. The motor driving apparatus according to claim 3, further comprising a low-pass filter for reducing an effect of high frequency components superimposed on said command value.

7. The motor driving apparatus according to claim 6, wherein the low-pass filter takes the maximum value of said command value within a prescribed time period as a command value.

8. The motor driving apparatus according to claim 1, wherein the current control means feeds discharge current from the charge/discharge control circuit when said value (4) or (5) increases to a prescribed value and stops the discharge current from the charge/discharge control circuit when said value (4) or (5) decreases to a prescribed value as a result of the feed operation.