System and method to sense current with passive impedance matching between current sensor and controller

Abstract

A system for sensing current includes a current sensor configured to sense current and having an output configured to output a voltage proportional to the current, a controller having an input with an associated internal resistance, the controller structured to sense voltage at the input, and a passive resistor electrically connected between the output of the current sensor and an input of the controller, the passive resistor configured to match impedances of the output of the current sensor and the input of the controller. The controller is structured to determine the current sensed by the current sensor based on the voltage sensed at the input of the controller, a resistance of the passive resistor, and the internal resistance associated with the input of the controller.

Description

SYSTEM AND METHOD TO SENSE CURRENT WITH PASSIVE IMPEDANCE MATCHING BETWEEN CURRENT SENSOR AND CONTROLLERCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application Serial No. 63 / 537,322, filed on September 8, 2023 and titled “SYSTEM AND METHOD TO SENSE CURRENT WITH PASSIVE IMPEDANCE MATCHING BETWEEN CURRENT SENSOR AND CONTROLLER” the disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION:

[0002] The disclosed concept relates generally to load management panels and, more particularly, to a system to method with impedance matching between a current sensor and a controller.BACKGROUND OF THE INVENTION:

[0003] Electrical loads are often connected to a load panel. The load panel receives power from a source, such as a utility panel, and provides the power to the electrical loads. A load panel may include electrical protection or electrical control devices to provide protection or control to the various circuit and electrical loads connected to the load panel.

[0004] A load management panel may be included in or coupled to a load panel. The load management panel may provide for monitoring of the various electrical loads coupled to the load panel and control of the protection or control devices in the load panel or the electrical loads. The load management panel may include a controller coupled to one or more sensors to monitor the various electrical loads and to control the protection or control devices, or the electrical loads.

[0005] The controller of the load management panel may control based on monitored characteristics. Thus, accurate monitoring of parameters of the various electrical loads is desirable.SUMMARY OF THE INVENTION:

[0006] In accordance with an aspect of the disclosed concept, a system for sensing current comprises: a current sensor configured to sense current and having an output configured to output a voltage proportional to the current; a controller having an input with an associated internal resistance, the controller structured to sense voltage at the input; and a passive resistor electrically connected between the output of the current sensor and an input of the controller, the passive resistor configured to match impedances of the output of the current sensor and the input of the controller, wherein the controller is structured to determine the current sensed by the current sensor based on the voltage sensed at the input of the controller, a resistance of the passive resistor, and the internal resistance associated with the input of the controller.

[0007] In accordance with an aspect of the disclosed concept, a method of sensing current comprises: providing a current sensor configured to sense current and having an output configured to output a voltage proportional to the current, a controller having an input with an associated internal resistance, the controller structured to sense voltage at the input, and a passive resistor electrically connected between the output of the current sensor and an input of the controller, the passive resistor configured to match impedances of the output of the current sensor and the input of the controller; and determining the current sensed by the current sensor based on the voltage sensed at the input of the controller, a resistance of the passive resistor, and the internal resistance associated with the input of the controller.BRIEF DESCRIPTION OF THE DRAWINGS:

[0008] A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

[0009] Figure 1 is a schematic diagram of a load management panel with an associated current sensor in accordance with an example embodiment of the disclosed concept.DETAILED DESCRIPTION OF THE INVENTION:

[0010] It will be appreciated that the specific elements illustrated in the figures herein and described in the following specification are simply exemplary embodiments of the disclosedconcept, which are provided as non-limiting examples solely for the purpose of illustration. Therefore, specific dimensions, orientations, assembly, number of components used, embodiment configurations and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting on the scope of the disclosed concept.

[0011] Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

[0012] As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

[0013] As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts or components, so long as a link occurs.

[0014] As employed herein, when ordinal terms such as “first” and “second” are used to modify a noun, such use is simply intended to distinguish one item from another, and is not intended to require a sequential order unless specifically stated.

[0015] As employed herein, the term “number” shall mean one or an integer greater than one (z.e., a plurality).

[0016] As employed herein, the term “processing unit” or “processor” shall mean a programmable analog and / or digital device that can store, retrieve, and process data; a microprocessor; a microcontroller; a microcomputer; a central processing unit; or any suitable processing device or apparatus.

[0017] The disclosed concept will now be described, for purposes of explanation, in connection with numerous specific details in order to provide a thorough understanding of the subject innovation. It will be evident, however, that the disclosed concept can be practiced without these specific details without departing from the spirit and scope of this innovation.

[0018] Figure 1 is a schematic diagram of a load management panel 10 with an associated current sensor 20 in accordance with an example embodiment of the disclosed concept. The load management panel 10 may be used to monitor and control power to loads and assist in applications such as electric vehicle charging. The load management panel 10 includes a controller 50 and is associated with the current sensor 20. The current sensor 20 may be used to sense a current associated with a circuit or device associated with the load management panel 10, such as, forexample and without limitation, an electrical load powered by a load panel associated with the load management panel 10. For example and without limitation, the current sensor 20 may be disposed around a conductor of an electrical circuit coupled to the monitored electrical load. The controller 50 may be configured to monitor the sensed current, and in some certain cases, initiate an action based on the sensed current. For example and without limitation, the controller 50 may control whether power is provided to the electrical load based on the sensed current. As an example, the controller 50 may stop power from being provided to the electrical load in the case of a fault detected in power provided to the electrical load. As another example, the controller 50 may stop power from being provided to the electrical load in the case of a load shedding event where the power being provided to the electrical load is above a predetermined threshold.

[0019] The output of the current sensor 20 and the input of the controller 50 have mismatched impedances, with the output of the current sensor 20 having a high output impedance and the input of the controller 50 having a low input impedance. If left unaddressed and the output of the current sensor 20 was directly connected to the input of the controller 50, the controller 50 would not be able to accurately monitor the sensed current due to the mismatched impedance. Some prior arrangements would place an operational amplifier with a high input impedance and a low output impedance between the current sensor 20 and the controller 50. However, the use of an operational amplifier increases costs and still would result in a current sensing error of about five percent.

[0020] In accordance with an example embodiment of the disclosed concept, the current sensor 20 has a high output impedance and the controller 50 has a low input impedance. A passive resistor 40 is electrically connected between the output of the current sensor 20 and the input of the controller 50. The inclusion of the passive resistor 40 between the output of the current sensor 20 and the input of the controller 50 results in an impedance matching between the output of the current sensor 20 and the input of the controller 50, and can improve the error in the controller’s 50 reading of the sensed current to less than one percent.

[0021] In some example embodiments of the disclosed concept, the current sensor 20 is self-powered and is configured to output a voltage based on the sensed current (e.g., without limitation, 0-10VDC), and the controller 50 has an internal resistance 60. The current may be sensed by measuring the voltage at the input of the controller 50 and taking into account the output voltage range of the current sensor 20, the resistance of the passive resistor 40, and the internalresistance 60 of the controller. For example, the voltage measured at the input of the controller 50 may be proportional to the voltage output by the current sensor 20. In some example embodiments, the controller 50 may have a programmable gain 70 associated with the input. The programmable gain 70 may also be taken into account when sensing the current in applications where the input of the controller 50 has an associated gain.

[0022] In some example embodiments, a connector 30 is disposed between the current sensor 20 and the controller to facilitate electrical connection between the current sensor 20 and the controller 50. In some example embodiments, the passive resistor 40 is mated to the connector 30.

[0023] In some example embodiments, the current sensor 20 is an EAC210SP manufactured by Eaton Corporation, which is a self-powered current sensor which has an output range of 0-10VDC. In some example embodiments, the controller 50 is an Easy 4 programmable logic controller manufactured by Eaton Corporation. The input of the controller 50 in some example embodiments has a 13k internal resistance 60. The passive resistor 40 is electrically connected between the output of the current sensor 20 and the input of the controller 50. In some example embodiments, the passive resistor 40 has a resistance of lOOk . The passive resistor 40 is also mated to the connector 30 between the current sensor 20 and the controller 50. The passive resistor 40 provides impedance matching between the output of the current sensor 20 and the input of the controller 50. The current sensed by the current sensor 20 is determined by measuring the voltage at the input of the controller 50, taking into account the output voltage range of the current sensor 20, the resistance of the passive resistor 40, and the internal resistance 60 of the input of the controller 50, as well as the gain 70 associated with the input of the controller where applicable.

[0024] Example embodiments of the disclosed concept provide a current sensor error of less than one percent, which is an improvement over prior arrangements that used an operational amplifier, which resulted in current sensing errors of five percent. Example embodiments of the disclosed concept also reduce development costs, unit cost, and time, which improving reliability and manufacturability.

[0025] It will be appreciated that the disclosed concept may include a method of sensing current. The method may include providing the current sensor 20 configured to sense current and having an output configured to output a voltage proportional to the current, the controller 50 having an input with an associated internal resistance 60, the controller 50 structured to sense voltage atthe input, and the passive resistor 40 electrically connected between the output of the current sensor 20 and an input of the controller 50, the passive resistor 40 configured to match impedances of the output of the current sensor 20 and the input of the controller 50. The method may further include determining the current sensed by the current sensor 20 based on the voltage sensed at the input of the controller 50, a resistance of the passive resistor 40, and the internal resistance 60 associated with the input of the controller 50.

[0026] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Claims

What is claimed is:

1. A system for sensing current, the system comprising: a current sensor configured to sense current and having an output configured to output a voltage proportional to the current; a controller having an input with an associated internal resistance, the controller structured to sense voltage at the input; and a passive resistor electrically connected between the output of the current sensor and an input of the controller, the passive resistor configured to match impedances of the output of the current sensor and the input of the controller, wherein the controller is structured to determine the current sensed by the current sensor based on the voltage sensed at the input of the controller, a resistance of the passive resistor, and the internal resistance associated with the input of the controller.

2. The system of claim 1, wherein the input of the controller has an associated programmable gain, and wherein the controller is structured to determine the current sensed by the current sensor based on the programmable gain associated with the input of the controller.

3. The system of claim 1, further comprising: a connector disposed between the output of the current sensor and the input of the controller, wherein the passive resistor is mated to the connector.

4. The system of claim 1 , wherein the resistance of the passive resistor is about lOOk .

5. The system of claim 1, wherein the internal resistance associated with the input of the controller is about 13kQ.

6. The system of claim 1, wherein the current sensor is a self-powered current sensor configured to output voltages in a range of 0-10VDC.

7. The system of claim 1, further comprising: a load management panel, wherein the controller is disposed in the load management panel, wherein the current sensor is configured to sense current associated with an electrical load, and wherein the controller is structured to control power to the electrical load based on the sensed current.

8. The system of claim 7, wherein the electrical load in an electric vehicle.

9. A method of sensing current, the method comprising: providing a current sensor configured to sense current and having an output configured to output a voltage proportional to the current, a controller having an input with an associated internal resistance, the controller structured to sense voltage at the input, and a passive resistor electrically connected between the output of the current sensor and an input of the controller, the passive resistor configured to match impedances of the output of the current sensor and the input of the controller; and determining the current sensed by the current sensor based on the voltage sensed at the input of the controller, a resistance of the passive resistor, and the internal resistance associated with the input of the controller.

10. The method of claim 9, wherein the input of the controller has an associated programmable gain, and wherein determining the current sensed by the current sensor is based on the programmable gain associated with the input of the controller.

11. The method of claim 9, further comprising: providing a connector disposed between the output of the current sensor and the input of the controller, wherein the passive resistor is mated to the connector.

12. The method of claim 9, wherein the resistance of the passive resistor is about lOOk .

13. The method of claim 9, wherein the internal resistance associated with the input of the controller is about 13kQ.

14. The method of claim 9, wherein the current sensor is a self-powered current sensor configured to output voltages in a range of 0-10VDC.

15. The method of claim 9, further comprising: providing a load management panel, wherein the controller is disposed in the load management panel, wherein the current sensor is configured to sense current associated with an electrical load, and wherein the controller is structured to control power to the electrical load based on the sensed current.

16. The method of claim 15, wherein the electrical load in an electric vehicle.

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