WO1993012528A1

WO1993012528A1 - Thin film sensors

Info

Publication number: WO1993012528A1
Application number: PCT/GB1992/002320
Authority: WO
Inventors: Amitava Basak; David Michael Rowe
Original assignee: University College Cardiff Consultants Limited
Priority date: 1991-12-12
Filing date: 1992-12-14
Publication date: 1993-06-24
Also published as: GB9126385D0

Abstract

In a laminated core for a transformer or other electrical apparatus, at least one lamination e.g. (10) has a sensor applied to it, the sensor being disposed at least partially between that lamination and an adjacent lamination. The sensor comprises a thin film structure deposited on a surface of the lamination: because it is of a thin film structure, the sensor does not create any significant gap between the adjacent laminations. The sensor may comprise a thermocouple (12) or a search coil for sensing the magnetic flux perpendicular to the plane of the lamination (sensor 14) or parallel to that plane (sensors 16, 18).

Description

THIN FILM SENSORS

This invention relates to sensors used in laminated transformer cores or in the laminated cores of other electrical apparatus e.g. electrical motors or electrical generators.

It is known to position .hermistor temperature sensors and miniature wire search coils between selected laminations of experimental transformer cores, in order that the temperature and magnetic field distributions throughout the core can be measured. These measurements have enabled the core designs to be improved. However, these sensors create air gaps between the adjacent laminations, thus affecting the parameters which are being measured.

We have now devised improved sensor arrangements for the laminated cores of transformers and other electrical apparatus, which substantially overcome these difficulties. In accordance with this invention, there is provided a laminated core for a transformer or other electrical apparatus, at least one lamination of the core having a sensor applied to it, the sensor being disposed at least partially between that lamination and an adjacent lamination, and the sensor comprising a thin film structure deposited on a surface of aid lamination.

Typically the or each thin film sensor has a thickness of several microns only, and so does not create an air gap of any significant thickness between the adjacent laminations. The laminated core may be provided with one or more thin film temperature sensors. Each temperature sensor may comprise a thermocouple sensor. In this case two conductive tracks of different metals (e.g. Ni-Cr and Ni-Al) are deposited on the surface of the respective lamination, and meet or form a junction at a point at wMch the temperature is to be measured or monitored: these racks extend to an edge of the core, where they connect with external circuitry.

Instead or in addition, the core may be provided with one or more magnetic field sensors, each sensor comprising a thin film search coil. This may comprise a coiled conductive track (e.g. of aluminium) deposited on the surface of the respective lamination at a point at which the magnetic field is to be measured or monitored: this coiled track is joined by lead-in tracks to an edge of the core, where they connect with external circuitry. Such a coiled track deposited on the surface of the lamination, i.e. lying in a plane parallel to the plane of the lamination, enables the component of field passing perpendicular to the latter plane to be measured. However, the thin film sensor deposited on the surface of the lamination may be built up to define a conductive coil lying in a plane perpendicular to the plane of the lamination, so that it can then be used to measure the component of field passing parallel to the plane of the lamination: preferably two such coils are formed, perpendicular to the plane of the lamination and in respective planes perpendicular to each other. Alternatively, a coil lying in a plane perpendicular to the plane of the lamination may be formed by providing two holes through the lamination, depositing an insulating layer over the inner surfaces of the holes and then depositing conductive material in the holes, to join the opposite ends of two conductive tracks deposited on the opposite surfaces of the lamination: typically such a search coil may measure 10 x 0.27mm. A search coil on the surface of the lamination may be of a square shape typically measuring 10 x 10mm, or of a circular shape typically of 10mm diameter. By providing a combination of different sensors, the direction and magnitude of magnetic field at different points in the core can be measured.

It is common for the metal plates forming core laminations to have an insulating film coated over their major surfaces. In such cases, the conductive tracks of the thin film sensors can be deposited directly over this insulating film. The conductive tracks may be formed by vacuum deposition, to a thickness typically in the range 120 to 500A. An embodiment of this invention will now be described, by way of example only and with reference to the accompanying drawing, the single Figure of which is a partly cut-away schematic perspective view of part of a laminated core for a transformer.

Referring to the drawing, there is shown a transformer core which comprises a stack of laminations, typically of grain oriented silicon iron. The stack of laminations is shown cut- away to illustrate sensors applied to one of the laminations 10. Firstly, and by way of example, a thermocouple sensor 12 is formed on one surface of the lamination 10: this thermocouple sensor comprises two thin film conductive tracks of different metals or alloys deposited on the lamination surface, and forming a junction at a point the temperature of which is to be monitored. Secondly, a search coil 14 is formed on the surface of the lamination 10, comprising a coiled conductive thin film track (e.g. of aluminium) deposited on the surface (e.g. by a vacuum deposition technique) . Thirdly, search coils 16,18 are formed in respective mutually- perpendicular planes each perpendicular to the plane of the lamination 10: each sensor comprises thin film tracks on opposite sides of the lamination, and extending through a pair of holes in the lamination. These search coils monitor the flex passing through the lamination 10.

Each of the sensors which has been described is joined by a pair of lead-in tracks to an edge of the lamination, where contacts are formed for connection to external circuitry. Each of sensors 14,16,18 as shown comprises a single-turn coil, but may instead comprise a plurality of turns. For example, each of search coils 16 and 18 may comprise two parallel series of holes in the laminations, with conductive tracks extending between and through the successive holes of the alternate series to form a multi-turn coil. Also, sensor 14 may be built up from alternating insulating and conductive layers to form multiple turns, for use as an H-coil (measuring the field strength in the air adjacent the surface of the lamination) .

Claims

1) A laminated core for a transformer or other electrical apparatus, at least one lamination of the core having a sensor applied to it, the sensor being disposed at least partially between that lamination and an adjacent lamination, and the sensor comprising a thin film structure deposited on a surface of said lamination.

2) A laminated core as claimed in claim 1, in which said sensor comprises a thin film temperature sensor deposited on said surface of said lamination.

3) A laminated core as claimed in claim 1, in which said sensor comprises a thin film coil deposited on said surface of said lamination.

4) A laminated core as claimed in claim 1, in which said sensor comprises a thin film coil arranged in a plane perpendicular to the plane of said lamination.

5) A laminated core as claimed in claim 4, in which said search coil comprises conductive tracks deposited on the opposite sides of said lamination and is completed by conductive tracks extending through two spaced-apart holes in the lamination.

6) A laminated core as claimed in any one of claims 3 to 5, in which said coil comprises a plurality of turns.

7) An electrical apparatus comprising a laminated core as claimed in any preceding claim.