POWER INVERTER WITH TWISTED AND SEGMENTED WIRE CONDUCTORS FOR CURRENT CONDUCTION AND SENSING

A power inverter includes first and second inputs and a plurality of power switches in communication with the first and second inputs. First, second and third outputs communicate with the plurality of power switches. First, second and third conductors are configured to connect the first, second and third outputs to an electric machine. Each of the first, second and third conductors comprise a plurality of twisted and segmented wires.

INTRODUCTION

The present disclosure relates to inverters and more particularly to power inverters for electric vehicles.

Electric vehicles (EVs) such as battery electric vehicles (BEVs), hybrid vehicles, and/or fuel cell vehicles include one or more electric machines and a battery system including one or more battery cells, modules and/or packs. A power control system is used to control charging and/or discharging of the battery system during charging and/or driving.

The power control system includes a power inverter that is arranged between the battery system and the electric machine. The power inverter includes solid copper busbars that connect the power inverter to the battery system and from the power inverter to the electric machine. The power inverter has a significant volume and weight due to the copper busbars.

At lower frequencies, the cross-section of the copper busbar conducts current in a uniform manner. As frequency increases, the cross-section of the copper busbar does not conduct current uniformly. At higher frequencies, current density increasingly accumulates in corners of the busbar due to Faraday induction effects (skin and proximity effects) leading to higher resistance.

The variation in current density with frequency also adversely affects sensing of phase currents using magnetic field based methods. Sensors are arranged in fixed locations adjacent to the copper busbars to sense magnetic fields produced by phase currents flowing through the copper busbars. Since the location of the current conducted by the copper busbars varies with frequency, it becomes more complex to determine the phase currents from the sensed magnetic fields.

SUMMARY

A power inverter includes first and second inputs and a plurality of power switches in communication with the first and second inputs. First, second and third outputs communicate with the plurality of power switches. First, second and third conductors are configured to connect the first, second and third outputs to an electric machine. Each of the first, second and third conductors comprise a plurality of twisted and segmented wires.

In other features, the plurality of power switches each include first terminals, second terminals and control terminals. The first terminals of first ones of the plurality of power switches are connected to the first input. Second terminals of second ones of the plurality of power switches are connected to the second input. The first, second and third outputs are connected between the second terminals of the first ones of the plurality of power switches and the first terminals of the second ones of the plurality of power switches.

In other features, the first, second and third conductors include first, second and third housings enclosing the plurality of twisted and segmented wires. A magnetic field sensor is arranged adjacent to the second housing of the second conductor. The magnetic field sensor is selected from a group consisting of an anisotropic magneto-resistive (AMR) sensor, a giant magneto-resistive (GMR) sensors, a tunnel magneto-resistive (TMR) sensors, and a Hall effect sensor.

In other features, the first, second and third conductors include first, second and third housings enclosing the plurality of twisted and segmented wires. At least two of the first, second and third housings extend in at least three planes.

In other features, the first housing includes a first portion, a second portion and a third portion. The first portion extends in a first plane. The second portion extends from the first portion in a direction transverse to the first plane. The third portion extends from the second portion in a second plane that is parallel to the first plane.

In other features, the second housing has rectangular shape and extends in the first plane spaced from the first portion of the first housing.

In other features, the third housing includes a first portion, a second portion, and a third portion, the first portion of the third housing extends in the first plane, the second portion of the third housing extends from the first portion in a direction transverse to the first plane, and the third portion extends from the second portion in a second plane that is transverse to the first plane.

In other features, each of the plurality of twisted and segmented wires comprise a first insulating sleeve and a plurality of multi-wire conductors arranged in the first insulating sleeve. The plurality of multi-wire conductors are wound around each other. Each of the multi-wire conductors includes multiple wires that are wound around each other inside a second insulating sleeve.

A power inverter includes first and second inputs and a plurality of power switches in communication with the first and second inputs. First, second and third outputs communicate with the plurality of power switches. First, second and third conductors are configured to connect the first, second and third outputs to an electric machine. Each of the first, second and third conductors comprise a plurality of twisted and segmented wires. Each of the plurality of twisted and segmented wires comprise a first insulating sleeve and a plurality of multi-wire conductors arranged in the first insulating sleeve. The plurality of multi-wire conductors are wound around each other. Each of the multi-wire conductors includes multiple wires that are wound around each other inside a second insulating sleeve. The first, second and third conductors include first, second and third housings enclosing the plurality of twisted and segmented wires. At least two of the first, second and third housings extend in at least three planes.

In other features, the plurality of power switches each include first terminals, second terminals and control terminals, the first terminals of first ones of the plurality of power switches are connected to the first input, second terminals of second ones of the plurality of power switches are connected to the second input, and the first, second and third outputs are connected between the second terminals of the first ones of the plurality of power switches and the first terminals of the second ones of the plurality of power switches.

In other features, the first, second and third conductors include first, second and third housings enclosing the plurality of twisted and segmented wires. A magnetic field sensor is arranged adjacent to the second housing of the second conductor. The magnetic field sensor is selected from a group consisting of an anisotropic magneto-resistive (AMR) sensor, a giant magneto-resistive (GMR) sensors, a tunnel magneto-resistive (TMR) sensors, and a Hall effect sensor.

In other features, the first housing includes a first portion, a second portion and a third portion, the first portion extends in a first plane, the second portion extends from the first portion in a direction transverse to the first plane, and the third portion extends from the second portion in a second plane that is parallel to the first plane.

In other features, the second housing has rectangular shape and extends in the first plane spaced from the first portion of the first housing.

In other features, the third housing includes a first portion, a second portion, and a third portion and the first portion of the third housing extends in the first plane. The second portion of the third housing extends from the first portion in a direction transverse to the first plane. The third portion extends from the second portion in a second plane that is transverse to the first plane.

DETAILED DESCRIPTION

A power inverter according to the present disclosure replaces copper busbars with segmented and twisted wire conductors to connect outputs of the power inverter to phases of an electric machine. The magnetic fields measured in response to the phase currents that are conducted by copper busbars vary with frequency due to Faraday induction effects (skin and proximity effects), it is difficult to accurately determine the phase currents from the sensed fields at both low and high frequencies. By replacing the copper busbars with the segmented and twisted wire conductors, the variation in the measured magnetic fields due to Faraday induction effects (skin and proximity effects) is reduced, which makes sensing the phase currents easier and more accurate at both low and high frequencies.

Referring now toFIGS.1and2, a power control system10for a battery system (BATT1) includes a power inverter12. The battery system BATT1 may include one or more battery cells, battery modules, and/or battery packs connected in series, parallel and/or combinations thereof. A contactor CON1 includes a first terminal connected to a first terminal of the battery system BATT1 and a second terminal connected to a capacitor C1 connected in parallel across inputs of the power inverter12. The contactor CON1 selectively connects a first terminal of the battery system BATT1 to the capacitor C1 and the power inverter12. While a single contactor CON1 is shown, two or more contactors can be used when more complex battery systems and/or switching are desired.

The power inverter12includes a plurality of power switches T1, T2, T3, T4, T5 and T6. First terminals of the power switches T1, T3 and T5 are connected to the second terminal of the contactor CON1. Second terminals of the power switches T1, T3 and T5 are connected to first terminals of the power switches T2, T4 and T6 and first, second and third phases of an electric machine14. Second terminals of the power switches T2, T4 and T6 are connected to a second terminal of the battery system BATT1. While a specific configuration of switches are shown for the power inverter12, other configurations can be used.

InFIG.2, control terminals of the power switches T1, T2, T3, T4, T5 and T6 (collectively power switches60) are connected to a controller50. The controller50is connected to the power switches60, sensors64and contactors68. The sensors64can include temperature sensors, current sensors, voltage sensors and/or other types of sensors. In some examples, the controller50also receives one or more voltage command signals based on demand. The controller50is configured to control states of the power switches T1, T2, T3, T4, T5 and T6 to transfer power from the battery system BATT1 to the electric machine14during operation as a motor (for propulsion) or from the electric machine14to the battery system BATT1 during operation as a generator (for regeneration).

Referring now toFIG.3, a perspective view of a copper busbar100is shown. While the cross-section of the copper busbar100conducts current relatively uniformly at lower frequencies, it does not conduct current uniformly at higher frequencies. Current density accumulates in corners of the copper busbar100(as shown at110) due to Faraday induction effects (skin and proximity effects), which leads to higher resistance. Since the phase currents that are conducted by the copper busbars vary with frequency, it becomes more complex to determine the phase currents from the sensed magnetic fields.

Referring now toFIG.4, rather than connecting the power inverter12to the electric machine14using copper busbars, the power inverter12according to the present disclosure is connected to the electric machine14using a plurality of twisted and segmented wire conductors150. The twisted and segmented wire conductors150include an outer insulating sleeve158. A plurality of multi-wire conductors160-1,160-1,160-2, ..., and160-X (collectively multi-wire conductors160) are arranged within the outer insulating sleeve158. In some examples, the multi-wire conductors160are wound around a core172. In other examples, the multi-wire conductors160are wound around each other without the core172.

Each of the multi-wire conductors160includes a plurality of wires164-1,164-2, ..., and164-X that are twisted around each other inside a second insulating sleeve166. In some examples, the wires164-1,164-2, ..., and164-X are also wound around a core (not shown). The twisted and segmented wire conductors150have significantly lower variation in current density due to reduced skin effect and hence lesser change in the magnetic fields with changes in frequency. As a result, determining the phase currents from the sensed magnetic fields is less complex.

Referring now toFIG.5, a power inverter200includes twisted and segmented wire conductors210-A,210-B and210-C to connect first, second and third phases of the power inverter200to first, second and third phases A, B and C, respectively, of the electric machine14. The twisted and segmented wire conductors210-A,210-B and210-C include a housing212and a plurality of twisted and segmented wires214arranged therein. In the example inFIG.5, the twisted and segmented wires214in each of the twisted and segmented wire conductors210-A,210-B and210-C are arranged in two rows and multiple columns. The twisted and segmented wire conductors210-A,210-B and210-C are connected to the power inverter200arranged side-by-side in a plane. More generally, the twisted and segmented wires214can be arranged in two or more rows and two or more columns or in other configurations such as round, square or other housing shapes.

Sensors222-A,222-B and222-C are arranged adjacent to the conductors210-A,210-B and210-C, respectively. In some examples, the sensors222-A,222-B and222-C are arranged on a printed circuit board220or other substrate that is arranged in a plane parallel to a plane including the conductors210-A,210-B and210-C. In some examples, spacing between the sensors222-A,222-B and222-C is maximized to reduce cross coupling between fields from different phases.

Referring now toFIG.6, a power inverter300includes twisted and segmented wire conductors320-A,320-B and320-C connecting first, second and third phases of the power inverter300to first, second and third phases A, B and C, respectively, of the electric machine14. Conductors310and312connecting the power inverter300to the battery system BATT1 can be copper busbars or other type of conductors.

The twisted and segmented wire conductors320-A,320-B and320-C are arranged in housings326-A,326-B and326-C and a plurality of twisted and segmented wires328arranged therein. In some examples, the housings326-A,326-B and326-C are made of plastic or another material that does not affect magnetic fields.

The outer housing326-A includes a first portion340located adjacent to the power inverter300, a second portion342extending from the first portion340and a third portion344extending from the second portion342. The first portion340extends from the power inverter300in a first plane. The second portion342extends from the first portion340in a direction transverse to the first plane. The third portion344extends from the second portion342in a second plane that is parallel to and spaced from the first plane. The outer housing326-B extends in the first plane laterally spaced from the first portion of the outer housing326-A. In some examples, the outer housing326-B has a rectangular cross-sectional shape, although other shapes can be used.

In some examples, the outer housing326-C includes a first portion350, a second portion352and a third portion354. The first portion350extends in the first plane. The second portion352extends from the first portion in a direction transverse to the first plane. The third portion354is rotated and extends from the second portion352in a second plane that is transverse to the first plane.

The arrangement of the twisted and segmented wire conductors320-A,320-B and320-C in different planes is to create x, y, and z fields that correspond to a, b, and c currents, respectively. This approach enables measurement of the a, b, and c currents with higher accuracy.

In the example inFIG.6, the twisted and segmented wires328in each of the twisted and segmented wire conductors320-A,320-B and320-C are arranged in four rows and multiple columns. More generally, the twisted and segmented wires214can be arranged in two or more rows and two or more columns or in other configurations such as round, square or other housing shapes.

Due to the arrangement inFIG.6, a single sensor can be used to sense the magnetic fields for the phases. A sensor360is arranged adjacent to the twisted and segmented wire conductors320-B, respectively. In some examples, the sensor360comprises a point field detector (PFD) such as an anisotropic magneto-resistive (AMR) sensors, a giant magneto-resistive (GMR) sensors, a tunnel magneto-resistive (TMR) sensors, a Hall effect sensor, or other suitable sensors that can detect field in the three dimensions X, Y and Z direction.

Referring now toFIGS.7-9, a matrix can be used to calculate currents from the sensed fields. The matrix includes dominant and frequency invariant terms. InFIG.7, the terms Dxa, Dyband Dzcdominate and all terms of the matrix are relatively frequency invariant due to the orientation of the sensor360and segmented and twisted conductors. InFIG.8, an example of sensed fields VBx, VBy, and VBzare shown. InFIG.9, the decoupled phase currents IA, IBand Ic are shown.

Referring now toFIGS.10and11, a power inverter500is similar to the power inverter300is shown. InFIG.10the orientation of the sensor360is rotated relative to the first plane as shown inFIG.10. InFIG.11, the terms Dxa, Dya, Dyb, Dyc, and Dzcdominate and all terms of the matrix are relatively frequency invariant. This orientation of the sensors provides the field information in a different form allowing addition of redundant sensors.