Electrical system

Patent metadata

Field	Value
Publication number	US-11204396-B2
Application number	US-201916437527-A
Country	US
Kind code	B2
Filing date	Jun 11, 2019
Priority date	Jun 12, 2018
Publication date	Dec 21, 2021
Grant date	Dec 21, 2021

Abstract

A method of monitoring an electrical system may include providing a ground fault detection unit, operating a transformer rectifier unit to provide DC power to a load, sensing, via a current sensor, a ground current at or about an output of the transformer rectifier, and/or monitoring a sensor output from the current sensor via the ground fault detection circuit. The ground fault detection circuit may be configured to detect ground faults at frequencies of at least 30 kHz.

First claim

What is claimed is:

1. A method of monitoring an electrical system, the method comprising:
providing a ground fault detection unit including:
a microcontroller;
a first ground fault detection circuit including a first portion and a second portion, the first portion and the second portion each connected to a first current sensor at respective inlets and to the microcontroller at respective outlets of the first and second portions; and
a second ground fault detection circuit including a first portion and a second portion, the first portion and the second portion each connected to a second current sensor at respective inlets and to the microcontroller at respective outlets of the first and second portions;

operating a transformer rectifier unit to provide DC power to a load;
sensing, via the first current sensor, a ground current at or about an output of the transformer rectifier unit; and
monitoring a sensor output from the first current sensor via the ground fault detection unit;
wherein the ground fault detection unit is configured to detect ground faults at frequencies of at least 30 kHz; and
wherein the first current sensor is configured as a high-frequency current sensor and the second current sensor is a low-frequency current sensor.

2. The method of claim 1 , wherein the ground fault detection unit is configured to detect ground faults at frequencies of at least 100 kHz.

3. The method of claim 1 , including sensing, via the second current sensor, the ground current;
wherein the first portion of the first ground fault detection circuit, the second portion of the first ground fault detection circuit, the first portion of the second ground fault detection circuit, and the second portion of the second ground fault detection circuit include respective filters.

4. The method of claim 3 , wherein the first current sensor is not a Hall Effect sensor; and the second current sensor is a Hall Effect sensor.

5. The method of claim 1 , wherein for the first ground fault detection circuit and/or the second ground fault detection circuit, the respective first portion and the respective second portion are separate and each includes separate electrical components configured to condition, filter, and/or amplify the sensor output from the respective current sensor.

6. The method of claim 5 , wherein the separate electrical components for each of the first portion and the second portion include signal conditioning circuitry, a filter, an inverting amplifier, a demodulator, a threshold comparator, and/or a timer circuit.

7. The method of claim 1 , including detecting a ground fault if the ground current exceeds a first threshold or a second threshold;
wherein the first threshold is a low frequency current threshold and the second threshold is a high frequency current threshold.

8. The method of claim 7 , wherein the second threshold is lower than the first threshold.

9. The method of claim 6 , wherein detecting the ground fault includes detecting the ground fault if the ground current exceeds the first threshold for a first period of time or if the ground current exceeds the second threshold for a second period of time.

10. The method of claim 9 , wherein the second period of time is longer than the first period of time.

11. The method of claim 6 , wherein the ground fault corresponds to ground current with a frequency of at least 25 kHz; and detecting the ground fault includes detecting the ground fault without a Fourier transform.

12. The method of claim 1 , wherein the first portion of the second ground fault detection circuit includes a demodulator configured to reduce a frequency of an output of the second current sensor.

13. The method of claim 1 , wherein the first portion of the first ground fault detection circuit includes a monostable multivibrator.

14. An electrical system, comprising:
a ground fault detection unit, including:
a microcontroller;
a first ground fault detection circuit including a first portion and a second portion, the first portion and the second portion each connected to a first current sensor at respective inlets and to the microcontroller at respective outlets of the first and second portions; and
a second ground fault detection circuit including a first portion and a second portion, the first portion and the second portion each connected to a second current sensor at respective inlets and to the microcontroller at respective outlets of the first and second portions;

wherein the first current sensor and the second current sensor are configured to sense current at or about an output of a DC power supply; and
wherein the first portion of the second ground fault detection circuit includes a demodulator configured to reduce a frequency of an output of the second current sensor.

15. The electrical system of claim 14 , including a second ground fault detection unit including a third ground fault detection circuit and a fourth ground fault detection circuit; the second ground fault detection unit is connected to an AC power supply; and the DC power supply is connected to the AC power supply and configured to convert AC power from the AC power supply to DC power for a variable frequency drive connected to an electric motor.

16. An electrical system, comprising:
a ground fault detection unit, including:
a first ground fault detection circuit including a first portion and a second portion, the first portion and the second portion connected to a first current sensor; and
a second ground fault detection circuit including a first portion and a second portion, the first portion and the second portion connected to a second current sensor;
wherein the first current sensor and the second current sensor are configured to sense current at or about an output of a DC power supply; and
wherein the first portion of the first ground fault detection circuit includes a low pass filter having a cutoff frequency; the second portion of the first ground fault detection circuit includes a first bandpass filter with a first passband; the first portion of the second ground fault detection circuit include a second bandpass filter with a second passband; and the second portion of the second ground fault detection circuit includes a third bandpass filter with a third passband.

17. The electrical system of claim 16 , wherein the third passband includes higher frequencies than the second passband; the second passband includes higher frequencies than the first passband; and the first passband includes frequencies above the cutoff frequency.

18. The electrical system of claim 16 , wherein the DC power supply is a transformer rectifier unit; the first passband corresponds to the DC power supply; the second passband corresponds to switching frequencies; and the third passband corresponds to harmonics of the switching frequencies.

19. The electrical system of claim 17 , wherein a maximum frequency of the third passband is at least about 100 kHz and a maximum frequency of the second passband is at least about 20 kHz.

20. The electrical system of claim 19 , wherein a maximum frequency of the second passband is at least about 4 kHz; and the cutoff frequency is about 10 Hz or less.

Assignees

• Eaton Intelligent Power Ltd

Inventors

• Bhalwankar Chaitanya
• Pahl Birger
• Schmalz Steve
• Chui Galen

Classifications

• G01R15/202

  using Hall-effect devices (Hall elements in arrangements for measuring electrical power G01R21/08) · CPC title

• H02H3/46

  responsive to frequency deviations · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H02H7/1216

  for AC-AC converters · CPC title

• H02H3/16

  responsive to fault current to earth, frame or mass (with balanced or differential arrangement H02H3/26 {; monitoring earth connection H02H5/105}) · CPC title