ELECTRICAL MACHINE WITH AN ACTIVE GROUNDING

• US 20180269753A1
• Filed: 10/04/2016
• Published: 09/20/2018
• Est. Priority Date: 10/08/2015
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: ABB Schweiz AG (ABB Limited)
• Inventors: RODRIGUEZ, Pedro, SAHOO, Subrat, PINTO, Cajetan, VANSKA, Klaus
• Granted Patent: US 11,342,819 B2
• Time in Patent Office: Days
• CPC Class Codes: H02K 11/0094 Structural association with other electrical or electronic devices
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: H02P 29/50 Reduction of harmonics
• CPC Class Codes: H02P 31/00 Arrangements for regulating or controlling electric motors not provided for in groups H02P1/00 - H02P5/00, H02P7/00 or H02P21/00 - H02P29/00

Abstract

A method for preventing a frequency component of a voltage from occurring in an electrical machine including the steps of: obtaining, either by measuring a voltage signal or a current signal from the electrical machine in time domain and transforming the measured signal into frequency domain, by simulating or deducing a first frequency component present in the electrical machine in absence of a grounding, the first frequency component representing a first undesired frequency higher than a limit frequency of 500 Hz; and providing the electrical machine with a first grounding at a grounding location, the first grounding including a resonant circuit resonating at the first undesired frequency. In order to get rid of harmful shaft voltages in the form of sharp voltage peaks at high frequencies, it is first necessary to determine at which undesired frequency or frequencies these voltage peaks occur. Only thereafter can a low impedance grounding be provided that works satisfactorily at the undesired frequency or frequencies.

Claims

1. A method for preventing at least one frequency component of a voltage from occurring in an electrical machine, the method comprising the steps of:

obtaining, either by measuring a voltage signal or a current signal from the electrical machine in time domain and transforming the measured signal into frequency domain, by simulating the electrical machine, or by deducing from operation settings of an inverter, a first frequency component present in the electrical machine in absence of a grounding, the first frequency component representing a first undesired frequency higher than a limit frequency of 500 Hz; and

providing the electrical machine with a first grounding at a grounding location, the first grounding comprising a resonant circuit resonating at the first undesired frequency.

2. The method according to claim 1, wherein the limit frequency is 1 kHz, 2 kHz, 4 kHz or 8 kHz.

3. The method according to claim 1, wherein the grounding location is at a stator core lamination or at a shaft of the electrical machine.

4. The method according to claim 1, wherein the first undesired frequency emerges from a common mode voltage.

5. The method according to claim 1, wherein the first frequency component is that with the highest voltage amplitude at frequencies above the limit frequency.

6. The method according to claim 1, wherein grounding impedance at the first undesired frequency is essentially zero.

7. The method according to claim 1, wherein resonant frequency of the resonant circuit is configured to be adjustable.

8. The method according to claim 1, wherein the resonant circuit comprises a capacitor and an inductor.

9. The method according to claim 1, wherein the method further comprises the steps of:

obtaining a second frequency component present in the electrical machine in absence of a grounding, the second frequency component representing a second undesired frequency higher than the limit frequency and different from the first undesired frequency; and

providing the electrical machine with a second grounding, the second grounding comprising a resonant circuit resonating at the second undesired frequency.

10. The method according to claim 1, wherein the obtaining of the first frequency component occurs during operation of the electrical machine.

11. The method according to claim 1, wherein the electrical machine comprises an inverter.

12. The method according to claim 11, wherein a switching frequency of the inverter is configured to change during operation of the electrical machine.

17. The method according to claim 2, wherein the grounding location is at a stator core lamination or at a shaft of the electrical machine

18. The method according to claim 2, wherein the first undesired frequency emerges from a common mode voltage

19. The method according to claim 2, wherein the first frequency component is that with the highest voltage amplitude at frequencies above the limit frequency

13. An electrical machine comprising:

a frequency component identifier configured to obtain, either by measuring a voltage signal or a current signal from the electrical machine in time domain and transforming the measured signal into frequency domain, by simulating the electrical machine, or by deducing from operation settings of an inverter, a first frequency component of a voltage present in the electrical machine in absence of a grounding, the first frequency component representing a first undesired frequency higher than a limit frequency of 500 Hz,

a first grounding at a grounding location, the first grounding preventing the first undesired frequency from occurring in the electrical machine, and the first grounding comprising a resonant circuit resonating at the first undesired frequency.

14. The electrical machine according to claim 13, wherein the limit frequency is 1 kHz, 2 kHz, 4 kHz or 8 kHz.

15. The electrical machine according to claim 13, wherein the frequency component identifier is configured to obtain the first frequency component during operation of the electrical machine.

16. The electrical machine according to claim 14, wherein the frequency component identifier is configured to obtain the first frequency component during operation of the electrical machine.