US-12618891-B2 - Sensor device for monitoring the dielectric strength of a dielectric fluid, in particular a fluid for the thermal conditioning of a battery

US12618891B2US 12618891 B2US12618891 B2US 12618891B2US-12618891-B2

Abstract

A sensor device for monitoring dielectric strength of a dielectric fluid has a sensor body which supports a sensitive part (SGi), designed for contact with the dielectric fluid. The sensitive part (SGi) comprises at least one pair of electrodes (E 1 , E 2 ) having respective surface portions arranged at a predefined micrometric or sub-micrometric distance, to define therebetween at least one detection gap between which part of the dielectric fluid is suitable to seep in. The sensor device has a circuit arrangement comprising: —means for generating an electric field between the two electrodes of the at least one pair of electrodes (E 1 , E 2 ) starting from a known supply voltage, and—means (V) for measuring a voltage representative of possible occurrence of an electric discharge between the two electrodes of the at least one pair of electrodes (E 1 , E 2 ) through the dielectric fluid ( 5 ) present in the at least one detection gap (G), following generation of the electric field.

Inventors

Marco Pizzi
Paolo BEGNAMINO
Marco FERRAGATTA
Matteo Rondano
Mauro Zorzetto

Assignees

ELTEK S.P.A.

Dates

Publication Date: 20260505
Application Date: 20220527
Priority Date: 20210601

Claims (18)

1 . A sensor device for monitoring dielectric strength of a dielectric fluid, the sensor device having a sensor body which supports a sensitive part designed for contact with the dielectric fluid, wherein the sensitive part comprises an electrically insulating support having a support face, at least one pair of thin-film metal electrodes being fixedly disposed side-by-side on said support face in a fixed position relative to each other, the thin-film metal electrodes having respective peripheral profiles, wherein facing portions of the peripheral profiles are set at a predefined micrometric or sub-micrometric distance from one another, to define therebetween at least one detection gap through which part of the dielectric fluid is able to penetrate, and wherein the sensor device has a circuit arrangement which comprises: a driving circuit configured to generate an electric field between the facing portions of the peripheral profiles of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes starting from a known or predefined supply voltage, a measuring circuit configured to measure a representative voltage indicative of a possible electric discharge between the facing portions of the peripheral profiles of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes through the dielectric fluid present in the at least one detection gap, following generation of the electric field, wherein the facing portions of the peripheral profiles of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes are spaced apart by a fixed distance between 100 nanometers and 20 micrometers, and wherein the circuit arrangement is configured to generate electric fields greater than 1 kV/mm between the facing portions of the peripheral profiles of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes starting from a supply voltage lower than 50 V.
2 . The sensor device according to claim 1 , wherein said supply voltage is comprised between 1 and 30 V, or between 3 and 10 V.
3 . The sensor device according to claim 1 , wherein the circuit arrangement is configured for bipolar driving, or for enabling inversion of electric polarity of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes between two successive detection cycles.
4 . The sensor device according to claim 1 , wherein the sensitive part comprises a plurality of pairs of thin-film metal electrodes fixedly disposed side-by-side on said support face in a fixed position relative to each other, wherein the facing portions of the peripheral profiles of the thin-film metal electrodes of each pair define a respective detection gap.
5 . The sensor device according to claim 1 , wherein: at least one thin-film metal electrode of the at least one pair of thin-film metal electrodes has a first portion of the respective peripheral profile with a generally pointed shape, that faces at the predefined distance a corresponding second portion of the peripheral profile of the other thin-film metal electrode of the at least one pair of thin-film metal electrodes, or at least one thin-film metal electrode of the at least one pair of thin-film metal electrodes has the peripheral profile thereof provided with at least one axially extended portion set at the predefined distance between two extended and parallel parts of a shaped portion of the peripheral profile of the other thin-film metal electrode of the at least one pair of thin-film metal electrodes, or the thin-film metal electrodes of the at least one pair of thin-film metal electrodes have the respective peripheral profiles each comprising a respective substantially comb-like portion, set in an interdigitated configuration at the predefined distance, said facing portions comprising the substantially comb-like portion of one of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes, and the comb-like portion of the other one of the thin-film metal electrodes of the at least one pair of thin-film metal electrodes.
6 . The sensor device according to claim 1 , also comprising a temperature detector.
7 . The sensor device according to claim 6 , wherein the circuit arrangement is configured for applying a temperature-based correction to a measured value of the representative voltage as a function of a temperature detected by the temperature detector.
8 . The sensor device according to claim 1 , wherein the sensitive part comprises at least one third thin-film metal electrode operatively associated with the at least one pair of thin-film metal electrodes, and wherein the circuit arrangement is configured for using the thin-film metal electrodes of the at least one pair of thin-film metal electrodes as a source electrode and a drain electrode, respectively, and the third thin-film metal electrode as a gate electrode.
9 . The sensor device according to claim 1 , wherein the sensitive part comprises at least one from among: a silicon oxide substrate on a silicon wafer, on the silicon oxide substrate there being set the at least one pair of thin-film metal electrodes; an electrically insulating substrate bearing a third thin-film metal electrode operatively associated with the at least one pair of thin-film metal electrodes, on which a layer of dielectric material is set, on which there is in turn formed the at least one pair of thin-film metal electrodes.
10 . The sensor device according to claim 1 , wherein the sensor body comprises at least one body part that houses a detection element bearing the sensitive part, the at least one body part having one or more openings or passages to enable the dielectric fluid to reach into contact with the at least one pair of thin-film metal electrodes of the sensitive part.
11 . The sensor device according to claim 10 , wherein annular sealing means are set between a wall of the at least one body part and the detection element, in such a way that the annular sealing means delimit, together with respective portions of said wall and of the detection element, a detection chamber within which the one or more openings or passages open, and which the sensitive part carried by the detection element faces.
12 . An electrical device having a casing which defines a containment volume within which an electrical part is arranged, the volume being adapted to receive a dielectric fluid, the electrical device comprising a sensor device according to claim 1 , for the monitoring of the dielectric strength of the dielectric fluid.
13 . The sensor device according to claim 1 , wherein each thin-film metal electrode has a thickness between 50 nanometers and 2 micrometers or between 100 and 500 nanometers.
14 . The sensor device according to claim 1 , wherein the sensitive part comprises a silicon oxide substrate on a silicon wafer, on the silicon oxide substrate there being set the at least one pair of thin-film metal electrodes, the silicon wafer having a thickness not smaller than the predefined distance.
15 . A sensor device for monitoring dielectric strength of a dielectric fluid, the sensor device having a sensor body which supports a sensitive part designed for contact with the dielectric fluid, wherein the sensitive part comprises at least one pair of electrodes having respective surface portions set at a predefined micrometric or sub-micrometric distance from one another, to define therebetween at least one detection gap through which part of the dielectric fluid is able to penetrate, wherein the sensor device has a circuit arrangement which comprises: means for generating an electric field between the electrodes of the at least one pair of electrodes starting from a known or predefined supply voltage, and means for measuring a representative voltage representing possible occurrence of an electric discharge between the electrodes of the at least one pair of electrodes through the dielectric fluid present in the at least one detection gap, following upon generation of the electric field, and wherein the circuit arrangement comprises at least: a voltage source to supply the known or predefined voltage, at least one capacitor having a known or predefined capacitance, controllable circuit means, for: connecting and disconnecting the at least one capacitor with respect to the voltage source, connecting and disconnecting the at least one capacitor with respect to the electrodes of the at least one pair of electrodes, and measuring circuit means for measuring a value of the representative voltage across the at least one capacitor after the electric field has been generated, or after the capacitor has been disconnected with respect to the voltage source and connected with respect to the electrodes of the at least one pair of electrodes.
16 . The sensor device according to claim 15 , wherein the circuit arrangement is configured for bipolar driving, or for enabling inversion of electric polarity of the electrodes of the at least one pair of electrodes between two successive detection cycles.
17 . A sensor device for monitoring dielectric strength of a dielectric fluid, the sensor device having a sensor body which supports a sensitive part designed for contact with the dielectric fluid, wherein the sensitive part comprises at least one pair of electrodes having respective surface portions set at a predefined micrometric or sub-micrometric distance from one another, to define therebetween at least one detection gap through which part of the dielectric fluid is able to penetrate, wherein the sensor device has a circuit arrangement which comprises: means for generating an electric field between the electrodes of the at least one pair of electrodes starting from a known or predefined supply voltage, and means for measuring a representative voltage representing possible occurrence of an electric discharge between the electrodes of the at least one pair of electrodes through the dielectric fluid present in the at least one detection gap, following upon generation of the electric field, and wherein the circuit arrangement comprises: a voltage source to supply the known or predefined voltage, a resistive voltage divider, comprising a plurality of reference resistors, controllable circuit means for selectively connecting and disconnecting the reference resistors between the voltage source and at least one electrode of the at least one pair of electrodes, measuring circuit means for measuring a value of the representative voltage across the terminals of the resistive voltage divider or between the electrodes of the at least one pair of electrodes after the electric field has been generated, or after each reference resistor has been connected between the voltage source and the at least one electrode of the at least one pair of electrodes.
18 . The sensor device according to claim 17 , wherein the circuit arrangement is configured for bipolar driving, or for enabling inversion of electric polarity of the electrodes of the at least one pair of electrodes between two successive detection cycles.

Description

This application is the U.S. national phase of International Application No. PCT/IB2022/055005 filed May 27, 2022 which designated the U.S. and claims priority to IT 102021000014312 filed Jun. 1, 2021, the entire contents of each of which are hereby incorporated by reference. FIELD OF INVENTION The present invention refers in general to sensor devices intended for monitoring one or more electrical quantities of a fluid, and to electrical devices equipped with a sensor of the type indicated. The invention has been developed with particular attention being paid to the monitoring of the dielectric strength of a dielectric fluid, preferably a fluid present in a casing of an electrical device, such as a fluid for the thermal conditioning of a battery. The described sensor device is however also suitable for use in other areas, or in combination with electrical devices other than a battery. BACKGROUND ART In recent times, the need of temperature conditioning of batteries in a more and more efficient manner, for example batteries that equip vehicles, is emerging. The technical solution adopted in some cases is to directly cool the battery cells by immersing them in a dielectric fluid, in order to maximize the heat exchange efficiency. The disadvantage of this solution is that, if the fluid used in contact with the battery cells does not guarantee a sufficient insulation, currents can be established inside the battery pack with significant loss of efficiency, up to potentially very dangerous outcomes. In order to keep under control the electrical insulation characteristics of the cooling fluid in which the battery cells are directly immersed, solutions based on the measurement of electrical parameters, such as measurements of dielectric constant, impedance, conductivity, have been proposed. However, these measurements have only an indirect correlation with the quantity of actual interest represented by the dielectric strength, i.e. the limit value of the electric field beyond which a conduction of electricity is produced through the fluid in question. In general, a fluid used for the thermal conditioning of a battery should ensure a minimum dielectric strength of not less than values of the order of 3 kV/mm. According to the current state of the art, the direct measurement of these dielectric strength values would require detection elements of macroscopic dimensions and based on the use of voltages being very high and expensive to generate, and which potentially behave as sources of electromagnetic noise and are dangerous for the possible triggering of avalanche phenomena on relatively large regions of space. On the other hand, the measurement of the electrical conductivity of the fluid alone does not always allow to accurately discriminate potentially dangerous situations. For these reasons, the approach generally followed is therefore to proceed with measurements of several different electrical quantities, such as the aforementioned dielectric constant, impedance and conductivity, correlating them with each other, with results that are not always satisfactory. Similar problems are also found in applications other than the exemplified one, wherein a dielectric fluid is used in combination with a generic electrical device, for example for its thermal conditioning. AIM AND SUMMARY OF THE INVENTION The present invention is based on the consideration of the fact that, particularly when the safety of an electrical device, such as a battery, is at stake, it would be desirable to have a sensor device that does not rely only on indirect measurements, or on complex correlations of indirect parameters and based on case systems that are hardly exhaustive. In this context, an aim of the present invention is essentially to obtain a sensor device capable of monitoring the degree of electrical insulation guaranteed by a fluid, in particular a thermal conditioning fluid of an electrical device, such as a battery. Another aim of the invention is to obtain a sensor device operating at a low voltage, but able to monitor also a high electrical resistance and/or a high electrical insulation of a fluid. Another aim of the invention is to obtain a sensor device capable of monitoring the electrical insulation of fluid, being of compact construction. An auxiliary aim of the invention is to obtain a sensor device that can be conveniently used even in cases where it is necessary to measure the degree of electrical insulation of substances with very low conductivity. One or more of the above aims, and other aims that will become clearer later, are achieved according to the present invention by a sensor device as described below. The aims of the invention are also achieved by an electrical device comprising such a sensor device. Preferential embodiments of the invention are indicated in the attached claims. The claims form an integral part of the technical teaching provided herein in relation to the invention. According to the invention, a se