MOTOR DRIVING DEVICE AND MEASURING METHOD

• US 20190162773A1
• Filed: 11/26/2018
• Published: 05/30/2019
• Est. Priority Date: 11/28/2017
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Chou, Norihiro, Ooi, Youichirou
• Granted Patent: US 10,641,817 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 27/025 Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence

Abstract

A motor driving device includes: a converter unit having a capacitor; a plurality of inverter units having a plurality of semiconductor switching elements and configured to convert a capacitor voltage across the capacitor into an AC voltage to drive a plurality of motors; a second switch configured to connect the negative-side terminal of the capacitor to ground; a first detector configured to detect a ground-referenced voltage; and a second detector configured to detect the capacitor voltage. The motor driving device controls the semiconductor switching elements to establish a measurement state for enabling measurement of an insulation resistance of a measurement target motor, determines that the ground-referenced voltage has converged when an amount of change in the waveform of the ground-referenced voltage detected by the first detector becomes equal to or lower than a threshold, and calculates the insulation resistance based on the ground-referenced voltage and the capacitor voltage.

Claims

1. A motor driving device for driving a plurality of motors, comprising:

a rectifier circuit configured to rectify an AC voltage supplied from an AC power supply via a first switch to thereby obtain a DC voltage;

a capacitor configured to smooth the DC voltage obtained by the rectifier circuit;

a plurality of inverter units each including upper arm semiconductor switching elements configured to connect a positive-side terminal of the capacitor with motor coils of a corresponding one of the motors, and lower arm semiconductor switching elements configured to connect a negative-side terminal of the capacitor with the motor coils, the inverter units being configured to drive the motors by converting a capacitor voltage across the capacitor into an AC voltage by switching operation of the upper arm semiconductor switching elements and the lower arm semiconductor switching elements;

a second switch configured to connect one terminal of the positive-side terminal and the negative-side terminal of the capacitor to ground;

a first detector configured to detect a ground-referenced current flowing between the one terminal of the capacitor and the ground, or a ground-referenced voltage between the one terminal of the capacitor and the ground;

a second detector configured to detect the capacitor voltage across the capacitor;

a switch control unit configured to establish a measurement state for enabling measurement of an insulation resistance of a measurement target motor of the motors by turning off the upper arm semiconductor switching elements and the lower arm semiconductor switching elements of all the inverter units to thereby stop operation of every motor while turning off the first switch and turning on the second switch, then turning on a semiconductor switching element that is connected to another terminal of the capacitor, among the upper arm and lower arm semiconductor switching elements to which the motor coils of the measurement target motor are connected, and turning on a semiconductor switching element that is connected to the one terminal of the capacitor, among the upper arm and lower arm semiconductor switching elements to which the motor coils of each of the motors other than the measurement target motor are connected;

a convergence determination unit configured to, in the measurement state, calculate a change amount in a waveform of the ground-referenced current or the ground-referenced voltage detected by the first detector, and determine that the ground-referenced current or the ground-referenced voltage has converged if the change amount becomes equal to or lower than a threshold; and

an insulation resistance calculator configured to, when the convergence determination unit determines that the ground-referenced current or the ground-referenced voltage has converged, calculate the insulation resistance of the measurement target motor, based on the ground-referenced current or the ground-referenced voltage detected by the first detector and the capacitor voltage detected by the second detector.

2. The motor driving device according to claim 1, wherein the convergence determination unit uses, as the change amount, an absolute value Δ

C of an amount of change in the ground-referenced current or the ground-referenced voltage during a predetermined time Δ

t.

3. The motor driving device according to claim 1, wherein, when Δ

C is an absolute value of an amount of change in the ground-referenced current or the ground-referenced voltage during a predetermined time Δ

t, the convergence determination unit uses Δ

C/Δ

t as the change amount.

4. The motor driving device according to claim 2, wherein the convergence determination unit gradually lengthens the predetermined time Δ

t with lapse of time.

5. The motor driving device according to claim 1, wherein the convergence determination unit uses, as the change amount, an absolute value of a derivative value of the waveform of the ground-referenced current or the ground-referenced voltage.

6. The motor driving device according to claim 1, wherein the convergence determination unit determines that the ground-referenced current or the ground-referenced voltage has converged if the ground-referenced current or the ground-referenced voltage has not changed by a reference change amount even after passage of a predetermined time.

7. A measuring method by which a motor driving device for driving a plurality of motors measures an insulation resistance of the motor, wherein,

the motor driving device includes:

a rectifier circuit configured to rectify an AC voltage supplied from an AC power supply via a first switch to thereby obtain a DC voltage;

a capacitor configured to smooth the DC voltage obtained by the rectifier circuit;

a plurality of inverter units each including upper arm semiconductor switching elements configured to connect a positive-side terminal of the capacitor with motor coils of a corresponding one of the motors, and lower arm semiconductor switching elements configured to connect a negative-side terminal of the capacitor with the motor coils, the inverter units being configured to drive the motors by converting a capacitor voltage across the capacitor into an AC voltage by switching operation of the upper arm semiconductor switching elements and the lower arm semiconductor switching elements;

a second switch configured to connect one terminal of the positive-side terminal and the negative-side terminal of the capacitor to ground;

a first detector configured to detect a ground-referenced current flowing between the one terminal of the capacitor and the ground, or a ground-referenced voltage between the one terminal of the capacitor and the ground; and

a second detector configured to detect the capacitor voltage across the capacitor,

the measuring method comprising;

a switch controlling step of establishing a measurement state for enabling measurement of the insulation resistance of a measurement target motor of the motors by turning off the upper arm semiconductor switching elements and the lower arm semiconductor switching elements of all the inverter units to thereby stop operation of every motor while turning off the first switch and turning on the second switch, then turning on a semiconductor switching element that is connected to another terminal of the capacitor, among the upper arm and lower arm semiconductor switching elements to which the motor coils of the measurement target motor are connected, and turning on a semiconductor switching element that is connected to the one terminal of the capacitor, among the upper arm and lower arm semiconductor switching elements to which the motor coils of each of the motors other than the measurement target motor are connected;

a convergence determining step of, in the measurement state, calculating a change amount in a waveform of the ground-referenced current or the ground-referenced voltage detected by the first detector, and determining that the ground-referenced current or the ground-referenced voltage has converged if the change amount becomes equal to or lower than a threshold; and

an insulation resistance calculating step of, when the convergence determining step determines that the ground-referenced current or the ground-referenced voltage has converged, calculating the insulation resistance of the measurement target motor, based on the ground-referenced current or the ground-referenced voltage detected by the first detector and the capacitor voltage detected by the second detector.

8. The measuring method according to claim 7, wherein the convergence determining step uses, as the change amount, an absolute value Δ

C of an amount of change in the ground-referenced current or the ground-referenced voltage during a predetermined time Δ

t.

9. The measuring method according to claim 7, wherein, when Δ

C is an absolute value of an amount of change in the ground-referenced current or the ground-referenced voltage during a predetermined time Δ

t, the convergence determining step uses Δ

C/Δ

t as the change amount.

10. The measuring method according to claim 8, wherein the convergence determining step gradually lengthens the predetermined time Δ

t with lapse of time.

11. The measuring method according to claim 7, wherein the convergence determining step uses, as the change amount, an absolute value of a derivative value of the waveform of the ground-referenced current or the ground-referenced voltage.

12. The measuring method according to claim 7, wherein the convergence determining step determines that the ground-referenced current or the ground-referenced voltage has converged if the ground-referenced current or the ground-referenced voltage has not changed by a reference change amount even after passage of a predetermined time.