Current transformer and method for converting a conductor current flowing in an electrical conductor to an output signal

Patent metadata

Field	Value
Publication number	US-9958481-B2
Application number	US-201414773380-A
Country	US
Kind code	B2
Filing date	Mar 31, 2014
Priority date	Apr 4, 2013
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

A current transformer arrangement, and method, include a current sensor for producing a sensor output voltage that is proportional to the input current flowing in a conductor; a first processing branch including a voltage calculating device for calculating the effective voltage value of the sensor output voltage; a second processing branch including a polarity detecting device having an input terminal connected with the current sensor output terminal to produce a polarity signal having one polarity when the conductor input current is either an alternating current, a hybrid current, or a direct current flowing in one direction, and the opposite polarity when the conductor input current is a direct current flowing in the opposite direction; and a multiplier device for modifying the effective voltage value to produce a signed effective voltage having a polarity corresponding with the polarity of the polarity signal. A modifying circuit modifies the signed effective voltage.

First claim

What is claimed is:

1. A current transformer arrangement, comprising:
(a) a current sensor having an input terminal connected with a conductor carrying a conductor input current, and an output terminal at which is produced a first output voltage that is proportional to the conductor input current;
(b) a first processing branch including a voltage calculating device connected with said current sensor output terminal for calculating an effective voltage value of said first output voltage, said first processing branch having a first output terminal;
(c) a second processing branch including a polarity detecting device having an input terminal connected with said current sensor output terminal, said second processing branch having a second output terminal at which a polarity signal is produced having:
(1) a first polarity when the conductor input current is either an alternating current, a hybrid current, or a direct current flowing in one direction, and
(2) a second polarity opposite to said first polarity when the conductor input current is a direct current flowing in the opposite direction; and

(d) a multiplier device having a first input connected with said first processing branch first output terminal, and a second input terminal connected with said second processing branch second output terminal, said multiplier device being operable to modify said effective voltage value to produce a signed effective voltage value having a polarity corresponding with the polarity of said polarity signal.

2. The current transformer arrangement defined in claim 1 , wherein said first processing branch includes a first low-pass frequency filter with high cut-off frequency, said first low-pass frequency filter being operable to filter high-frequency interference signals from said current sensor output voltage.

3. The current transformer arrangement as defined in claim 2 , wherein said first low-pass frequency filter has an adjustable cut-off frequency.

4. The current transformer arrangement as defined in claim 2 , wherein said first low-pass frequency filter has an adjustable step response time.

5. The current transformer arrangement as defined in claim 2 , wherein said voltage calculating device has an adjustable time constant.

6. The current transformer arrangement defined in claim 2 , wherein said second processing branch includes a second frequency filter operable to smooth out said current sensor output voltage, thereby to detect the sign of the direct current component of the conductor current input.

7. The current transformer arrangement defined in claim 1 , and further including:
(e) an output modifying circuit for modifying said signed effective value voltage for use by the user.

8. The current transformer arrangement defined in claim 7 , wherein said output modifying circuit includes an adder for superimposing an offset voltage upon said signed effective value voltage.

9. The current transformer arrangement defined in claim 7 , wherein said output modifying circuit includes an adder for adding a scaling factor upon said signed effective voltage.

10. The current transformer arrangement defined in claim 7 , wherein said output modifying circuit includes a signal selecting device for selecting either a current output signal or a voltage output signal.

11. The current transformer arrangement defined in claim 1 , wherein said current sensor is a Hall effect sensor.

12. The current transformer arrangement defined in claim 1 , wherein said current sensor is a shunt resistor.

13. The current transformer arrangement defined in claim 1 , and further including an analog/digital converter connected with the output of said output modifying circuit for supplying a control signal to an automation control system.

14. A method for converting a conductor current flowing in an electrical conductor into an output signal, comprising the steps of:
(a) detecting the conductor current by means of a current transforming sensor to produce a sensor output voltage that is proportional to the conductor current;
(b) calculating by means of a calculating device the effective voltage value of said sensor output voltage;
(c) generating by means of a polarity detecting device a polarity signal as a function of the polarity of said sensor output voltage;
(d) multiplying said effective voltage value by means of a multiplying device with a positive or negative factor corresponding with the polarity of said sensor output voltage, thereby to produce a signed effective value; and
(e) modifying said signed effective value by an output modifying circuit to produce a modified output signal corresponding with the sign of said signed effective value.

15. The method as defined in 14 , and further including the step of scaling said signed effective value by a scaling device by a scaling factor.

16. The method as defined in claim 14 , and further including the step of adding by an adder device an offset voltage to said signed effective value.

17. The method as defined in claim 14 , and further including the step of applying said modified output signal to an automation control system.

18. The method as defined in claim 14 , wherein said polarity signal has:
(1) a first polarity when said conductor current is a pure alternating current, a hybrid alternating current, or a direct current flowing in a first direction, and
(2) a second polarity opposite to said first polarity when said conductor current is a direct current flowing in the opposite direction.

Assignees

• Weidmueller Interface Gmbh & Co Kg

Inventors

• Gerkens Michael
• Heggemann Christian
• Schlingmann Hans

Classifications

• G01R19/02 Primary

  Measuring effective values, i.e. root-mean-square values · CPC title

• H02M2001/0009

  Electricity · mapped topic

• G01R19/2509

  Details concerning sampling, digitizing or waveform capturing · CPC title

• G01R15/18

  using inductive devices, e.g. transformers · CPC title

• G01R15/202 Primary

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