Patent Description:
Many conventional open loop current transducers comprise a magnetic core with an air gap in which a magnetic field detector is positioned for measuring a magnetic field induced by a primary conductor carrying a current to be measured by the magnetic core. Such open loop type of current transducers are widely used in current sensing applications in view of their durability, large current measuring range and low cost, in particular including the low cost of the electronics required to drive the current transducer circuit.

In many conventional open loop transducers for a large operating range, it is typical to provide a single magnetic core surrounding a central passage through which a primary conductor bar extends, the magnetic core comprising an airgap in which a magnetic field detector, typically a Hall effect detector, is mounted. In many high current applications, the primary conductor bar forms part of the transducer and has connection ends configured to be connected to a conductor carrying the current to be measured. The integration of the primary conductor in the transducer facilitates installation and connection of the transducer to the system in which it is implemented to measure a primary current. Integration of the primary conductor bar in the current transducer also avoids a more complex current transducer arrangement requiring a split magnetic core, for instance mounted in a two-part hinge coupled housing that can be assembled around a primary conductor bar. It however has drawbacks in that it increases the overall size of the arrangement current transducer and external system to which the current transducer is coupled. The additional interconnections between the primary conductor bar section and the external circuit are also sources of potential problems especially in harsh environments with vibration, and mechanical and thermally caused stresses.

In particular, in power inverter applications which form components that require further integration in the external systems such as motor drives, the available space for integrating components such as current transducers may be rather limited while the requirement for low cost, durable, accurate and easy to install current transducer subsists.

Various current measuring devices for mounting against a primary conductor bar for measuring a current flowing in the primary conductor bar are disclosed in <CIT>, <CIT>, <CIT>, <CIT>.

In view of the foregoing, it is an object of this invention to provide a compact, yet robust, durable and reliable open-loop current transducer that is also economical to produce and install.

It is advantageous to provide an open loop current transducer that has a large operating range and that is for use in harsh operating environments in particular subject to mechanical vibrations, shock and large thermal variations such as in automotive or other mobile applications.

A specific object of the invention is to provide a compact yet robust, durable and reliable open loop current transducer for measuring currents in a power inverter, in particular for electric motor drives, for instance electrical motors for automotive applications, that is economical to produce and install.

In certain applications in particular power inverters for electrical motor drives, the current transducer should be able to operate in a current measurement range of up to <NUM> A.

Objects of the invention have been achieved by providing a current transducer module according to claim <NUM>.

Dependent claims set out various advantageous features of embodiments of the invention.

Disclosed herein is a current transducer module comprising.

In an advantageous embodiment, the magnetic field detectors are mounted on a first primary conductor facing side of the circuit board and the magnetic core part is mounted on a second side of the circuit board, opposite the first primary conductor facing side.

In an advantageous embodiment, the housing further comprises locating ribs upstanding from the base wall within the internal cavity, upper edges of the locating ribs positioned against the magnetic core part.

In an advantageous embodiment, the circuit board comprises slots receiving the locating ribs therethrough.

In an advantageous embodiment, the magnetic core part comprises a substantially linear beam portion and at each core end a transverse projecting stub portion.

In an advantageous embodiment, the housing comprises one or more locating elements protruding outwardly from one or more lateral sides of the housing.

In an advantageous embodiment, the locating ribs comprise at least one locating rib on each of at least three side walls of the housing.

In an advantageous embodiment, the housing comprises a base portion including the base wall and the side walls, and a cover portion separately formed from the base portion and configured to be assembled to the base portion to close the internal cavity.

In an advantageous embodiment, the current transducer module further comprises electrical contacts connected to the circuit board and extending from the circuit board through the top wall for connection to external contacts.

Also disclosed herein is a system comprising the current transducer module according to any preceding embodiment and a primary conductor module, wherein the current transducer module is configured to be mounted on the primary conductor module; and the primary conductor module comprises a housing, a primary conductor bar lodged partially within the housing, and a magnetic core part mounted in the housing adjacent a first side of the primary conductor bar such that the magnetic core part of the primary conductor module and the magnetic core part of the current transducer module surround the primary conductor bar and define airgaps in which the magnetic field detectors are positioned.

Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations.

Referring to the figures a current transducer module <NUM> configured to be assembled to a primary conductor module <NUM> of an external system, such as a power inverter for an electrical drive, is illustrated.

The primary conductor module <NUM> comprises a housing <NUM>, a primary conductor bar <NUM> carrying a primary current for instance powered by a power inverter for supplying a phase current to an electrical motor. The primary conductor module may comprise a circuit board (not shown) and contacts <NUM> for power and signal communication with electronic components on the circuit board of the primary conductor module <NUM>. The primary conductor module <NUM> further comprises a magnetic core part <NUM> positioned adjacent a first side 17a of the primary conductor bar <NUM>, opposite a second side 17b of the primary conductor bar <NUM> facing an interface surface configured for receiving the current transducer module <NUM>. The primary conductor bar <NUM> may have a substantially rectangular cross-section with a width W and a height H, with first and second opposed major surfaces defining above mentioned first and second sides 17a, 17b, and third and fourth opposed minor surfaces 17c.

The current transducer module <NUM> comprises a housing defining an internal cavity <NUM>, and a magnetic core part <NUM>, magnetic field detectors 8a, 8b, and a circuit board <NUM> mounted in the internal cavity <NUM>. The housing <NUM> has an outer primary conductor mounting side <NUM>, a top wall side <NUM>, and lateral sides <NUM> joining the top wall side to the primary conductor mounting side <NUM>. The primary conductor mounting side <NUM> is configured to be mounted against a transducer receiving side <NUM> of the primary conductor module <NUM>.

The transducer receiving side <NUM> may advantageously be recessed relative to an outer surface <NUM> of the primary conductor module <NUM> such that the current transducer module <NUM> is partially inserted into the recess when assembled to the primary conductor module <NUM>. The recess is surrounded by a recess side wall <NUM> having a perimeter with the shape of the perimeter of the primary conductor mounting side <NUM> of the current transducer module <NUM>.

The primary conductor mounting side <NUM> of the current transducer module has a flat portion in a mounting plane M parallel or substantially parallel to the plane of the second side of the primary conductor bar <NUM> when the current transducer module <NUM> is assembled to the primary conductor module <NUM>.

The magnetic field detectors 8a, 8b comprise first and second magnetic field detectors mounted on the circuit board <NUM> in a spaced apart relationship with the spacing corresponding substantially to the width W of the primary conductor bar <NUM>. Each magnetic field detector 8a, 8b is thus configured to be positioned approximately adjacent a corresponding minor side 17c of primary conductor bar <NUM>.

The magnetic core part <NUM> comprises a substantially linear beam shape extending between first and second ends, each end overlying a corresponding one of the magnetic field detectors 8a, 8b. The magnetic core may comprise short stubs 6a, 6b extending from each end towards the corresponding magnetic field detector such that the magnetic core part forms a flat "U" shaped part. The magnetic field detectors are mounted on a first side, forming a primary conductor facing side <NUM> of the circuit board <NUM>, and the magnetic core part is mounted on the opposite second side <NUM> of the circuit board <NUM>. The circuit may be provided with further electrical or electronic components (not shown) and comprise contacts <NUM> for signal and power interconnection to the circuit board including the magnetic field detectors 8a, 8b. The magnetic field detectors 8a, 8b may be in the form of ASICs (Application Specific Integrated Circuits) comprising for instance Hall effect magnetic field detector as per se well known in the art of current transducers.

The housing <NUM> may comprise locating ribs <NUM> formed in the internal cavity <NUM> upstanding from a base wall <NUM> of the housing, the locating ribs <NUM> having an upper edge <NUM> adjacent the magnetic core part <NUM> and against which the magnetic core part <NUM> may rest and be positioned. The locating ribs <NUM> may thus serve as positioning elements that accurately position the core ends 6a, 6b of the magnetic core part <NUM> relative to the base wall <NUM> and thus to the primary conductor mounting side surface <NUM> of the housing <NUM>. This ensures a calibrated accurate airgap distance formed between the magnetic core part core ends 6a, 6b and the core ends 7a, 7b of the magnetic core part <NUM> in the primary conductor module <NUM> when the current transducer module is placed against the transducer receiving side <NUM> of the primary conductor module <NUM>.

The circuit board <NUM> is provided with corresponding slots <NUM> for receiving the locating elements <NUM> therethrough.

The position of the circuit board <NUM> relative to the base wall <NUM> of the housing may be provided by one or more protuberances upstanding from the base wall configured to provide a gap between the first side <NUM> of the circuit board and the base wall <NUM> to fit the thickness of the magnetic field detectors 8a, 8b. The magnetic field detectors in the form of ASICs, are thus sandwiched between the circuit board <NUM> and the housing base wall <NUM>.

When the base wall <NUM> of the current transducer module is mounted against the transducer module receiving side the surface <NUM> of the primary conductor module <NUM>, the core ends 6a, 6b of the magnetic core part <NUM> and the magnetic field detectors 8a, 8b are positioned substantially opposite and facing the magnetic core part ends 7a, 7b of the magnetic core part <NUM> mounted in the primary conductor module <NUM>. The magnetic field detectors 8a, 8b are thus positioned in airgaps formed by the two magnetic core parts <NUM>, <NUM> when the current transducer module <NUM> is assembled to the primary conductor module <NUM>, the magnetic core parts <NUM>, <NUM> surrounding the primary conductor bar <NUM>.

The housing <NUM> of the current transducer module advantageously comprises locating elements <NUM> formed on one or more lateral sides <NUM> cooperating with complementary locating elements <NUM> formed on a corresponding one or more lateral sides of the recess side wall <NUM> of the housing <NUM> of the primary conductor module <NUM>. The locating elements <NUM> may for instance be in the form of protuberances (flanges, ribs) extending outwardly from the lateral sides <NUM>, engaging in complementary cavities or slots formed in the recess side wall <NUM> of the primary conductor module housing <NUM>. The locating elements <NUM> serve to ensure correct assembly and accurate registration of the current transducer module <NUM> to the primary conductor module <NUM> when the two parts are assembled together.

The current transducer module may further be provided with mounting posts <NUM> extending from the primary conductor mounting side <NUM> of the base wall <NUM> for insertion in corresponding mounting holes in the receiving side <NUM> of the primary conductor module housing <NUM>. The current transducer module <NUM> may be welded, adhesively bonded, or fixed by screws or other mechanical fixing means to the primary conductor module <NUM> once assembled thereto.

The housing <NUM> of the current transducer module may advantageously be provided in two parts comprising a base portion 4a including the base wall <NUM> and side walls <NUM> upstanding therefrom defining the internal cavity <NUM>, and a cover portion 4b that mounts to the base portion to close the internal cavity <NUM>, the cover portion 4b forming a top wall <NUM>.

In a variant, the housing <NUM> may be provided without a cover part, and the internal cavity <NUM> filled with an insulating potting material, or even without a potting material, simply covered by an external unit that mounts over the top of the transducer module and connects to the contacts <NUM>.

The cover portion 4b may be provided with orifices to receive the contacts <NUM> therethrough for plugging connection or for solder or weld connection to contacts of an external circuit, for instance an external circuit board that may be mounted against the top wall <NUM> of the housing. The contacts <NUM> of the primary conductor module <NUM> may be connected to the same external circuit board as the contacts <NUM> of the current transducer module <NUM>.

Claim 1:
A current transducer module (<NUM>) comprising
- a housing having a base wall (<NUM>) and side walls (<NUM>) forming an internal cavity (<NUM>),
- a magnetic core part (<NUM>),
- magnetic field detectors (8a, 8b), and
- a circuit board (<NUM>),
the magnetic core part, magnetic field detectors, and the circuit board mounted within the internal cavity (<NUM>) of the housing (<NUM>),
the magnetic core part (<NUM>) extending from a first core end (6a) to a second core end (6b), the magnetic field detectors comprising a first magnetic field detector (8a) positioned opposite the first core end (6a) and a second magnetic detector (8b) positioned opposite the second core end (6b), the magnetic field detectors (8a, 8b) connected to the circuit board and arranged substantially co-planar with respect to each other, characterized in that the magnetic field detectors (8a, 8b) are mounted against the base wall (<NUM>) of the housing (<NUM>) and the magnetic core part is mounted above the magnetic field detectors such that the magnetic field detectors are positioned in a gap between the housing base wall and the magnetic core part.