GB2530255A

GB2530255A - A lead frame for an electric motor or generator

Info

Publication number: GB2530255A
Application number: GB1416243.2A
Authority: GB
Inventors: Geoffrey Henfryn Owen
Original assignee: Protean Electric Ltd
Current assignee: Oak Investment Properties Xii LP
Priority date: 2014-09-15
Filing date: 2014-09-15
Publication date: 2016-03-23
Anticipated expiration: 2034-09-15
Also published as: GB2530255B; GB201416243D0

Abstract

A lead frame connects an inverter to a DC power supply and to a coil winding of an electric motor or generator. A continuous conductor 800 is encapsulated in a plastic housing and comprises a connection 810 to a power supply and connections to the inverter extending from the housing; and has a section 810 to isolate the inverter from the power supply at a predetermined current load. A second conductor 900 is also encapsulated in the plastic housing and has a connection 920 to a coil winding and a connection to the inverter also extending from the housing. The two conductors 800, 900 may be on opposite sides of the housing, which can also enclose the inverter. Isolating section 810 may be: made from copper; visible through the housing; and melt at the predetermined current load. There may be further conductors 920 connecting the inverter with respective coil windings. Conductor 800 may connect the inverter to a positive power rail and there may be a further conductor connecting the inverter with a negative power rail. There may be plural power modules comprising the lead frame for an electric vehicle wheel motor.

Description

A LEAD FRAME FOR AN ELECTRIC MOTOR OR GENERATOR

The present invention relates to a lead frame, in particular a lead frame for coupling an inverter for an electric motor or generator to a DC power supply.

Electric motor systems typically include an electric motor, with a control unit arranged to control the power of the electric motor. Examples of known types of electric motor include the induction motor, synchronous brushless permanent magnet motor, switched reluctance motor and linear motor. In the commercial arena three phase electric motors are the most common kind of electric motor available.

A three phase electric motor typically includes three coil sets, where each coil set is arranged to generate a magnetic field associated with one of the three phases of an alternating voltage.

To increase the number of magnetic poles formed within an electric motor, each coil set will typically have a number of coil sub-sets that are distributed around the periphery of the electric motor, which are driven to produce a

rotating magnetic field.

By way of illustration, Figure 1 shows a typical three phase electric motor 10 having three coil sets 14, 16, 18. Each coil set consists of four coil sub-sets that are connected in series, where for a given coil set the magnetic field generated by the respective coil sub-sets will have a common phase.

The three coil sets of a three phase electric motor are typically configured in either a delta or wye configuration.

A control unit for a three phase electric motor having a DC power supply will typically include a three phase bridge inverter that generates a three phase voltage supply for driving the electric motor. Each of the respective voltage phases is applied to a respective coil set of the electric motor.

A three phase bridge inverter includes a number of switching ]0 devices, for example power electronic switches such as Insulated Gate Bipolar Transistor (IGET) switches, which are used to generate an alternating voltage from a DC voltage supply.

However, should an inverter fail this can cause large, uncontrollable currents to flow in the motor coils, which can result in the motor generating undesirable torques and/or failure of other motor components.

This problem is exacerbated for an electric motor having a number of sub motors that are arranged to operate independently of each other, where uncontrollable current flows resulting from an inverter failure in one sub motor may cause other sub motors to fail.

One solution to this problem has been the use of electrical fuses, where typically a fuse is placed between a DC busbar, which is used to provide a DC current to a motor inverter, and a lead frame, which is used for coupling the legs of an inverter to the DC busbar. As is well known to a person skilled in the art, a lead frame provides a mechanism for electrically connecting components, where a lead frame corresponds to one or more electrical conductors used for electrically connecting components, with the one or more electrical conductors being over moulded with an electrically insulating plastic material. The over moulded electrically insulating plastic, which forms part of the lead frame, is used both as an insulator and structural suppcrt fcr the electrical conductors.

The fuse is arranged to electrically isolate the DC busbar from the inverter should the current load exceed a predetermined value, thereby preventing large, unwanted ]0 current flows tc the failed inverter.

However, the type of fuses reguired for an electric motor used to provide drive torque for a vehicle are typically large and expensive. :is

This problem is further exacerbated for an integrated electric motor design in which the associated electric motor control unit is integrated with the electric motor, where space is typically at a premium.

It is desirable to improve this situation.

In accordance with an aspect of the present invention there is provided a lead frame according to the accompanying claims.

The present invention provides the advantage of allowing a lead frame, which couples an inverter to a DC voltage supply, to electrically isolate the inverter from the DC voltage supply upon an inverter fault occurring without the need for a separate fuse.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates a prior art three phase electric motor; Figure 2 illustrates an exploded view of a motor embodying the present invention; Figure 3 illustrates an exploded view of the eleotric motor shown in Figure 1 from an alternative angle; Figure 4 illustrates an electric motor according to an embodiment of the present invention; Figure 5 illustrates an exploded view of a control device for an electric motor acoording to an embodiment of the present invention; Figure 6 illustrates a second exploded view of a control device for an eleotric motor according to an embodiment of the present invention; Figure 7 illustrates a lead frame according to an embodiment of the present invention; Figure 8 illustrates a transparent view of a lead frame according to an embodiment of the present invention; Figure 9 illustrates a power source busbar according to an embodiment of the present invention; Figure 10 illustrates a pair of power source busbars according to an embodiment of the present invention; Figure U illustrates an electric motor according to an embodiment of the present invention; Figure 12 illustrates a power substrate assembly; Figure 13 illustrates a control device according to an embodiment of the present invention.

The embodiment of the invention described is for a lead frame for coupling an inverter, for an electric motor or generator, to a DC power supply, where preferably the electric motor is for use in a wheel of a vehicle. However the electric motor may be located anywhere within the vehicle. The motor is of the type having a set of coils being part of the stator for attachment to a vehicle, radially surrounded by a rotor carrying a set of magnets for attachment to a wheel. For the avoidance of doubt, the various aspects of the invention are equally applicable to an electric generator having the same arrangement. As such, the definition of electric motor is intended to include electric generator. In addition, some of the aspects of the invention are applicable to an arrangement having the rotor centrally mounted within radially surrounding coils. As would be appreciated by a person skilled in the art, the present invention is applicable for use with other types of electric motors.

For the purposes of the present embodiment, as illustrated in Figure 2 and Figure 3, the in-wheel electric motor includes a stator 252 comprising a heat sink 253, multiple coils 254, two control devices 400 mounted on the heat sink 253 on a rear portion of the stator for driving the coils, and an annular capacitor (not shown) , otherwise known as a DC link capacitor, mounted in a recess 258 on the stator within the inner radius of the control devices 400. The coils 254 are formed on stator tooth laminations to form coil windings. A stator cover 256 is mounted on the rear portion of the stator 252, enclosing the control devices 400 to form the stator 252, which may then be fixed to a vehicle and does not rotate relative to the vehicle during use.

Each control device 400 includes two inverters 410 and control logic 420, which in the present embodiment includes a processor, for controlling the operation of the inverters 410, which is schematically represented in Figure 4.

The annular capacitor is coupled between the inverters 410 and the electric motor's DC power source for reducing voltage ripple on the electric motor's power supply line, otherwise known as the DC busbar, and for reducing voltage overshoots during operation of the electric motor. For reduced inductance the capacitor is preferably mounted adjacent to the control devices 400.

A rotor 240 comprises a front portion 220 and a cylindrical portion 221 forming a cover, which substantially surrounds the stator 252. The rotor includes a plurality of permanent magnets 242 arranged around the inside of the cylindrical portion 221. For the purposes of the present embodiment 32 magnet pairs are mounted on the inside of the cylindrical portion 221. However, any number of magnet pairs may be used.

The magnets are in close proximity to the coil windings on the stator 252 so that magnetic fields generated by the coils interact with the magnets 242 arranged around the inside of the cylindrical portion 221 of the rotor 240 to cause the rotor 240 to rotate. As the permanent magnets 242 are utilized to generate a drive torque for driving the electric motor, the permanent magnets are typically called drive magnets.

The rotor 240 is attached to the stator 252 by a bearing block 223. The bearing block 223 can be a standard bearing block as would be used in a vehicle to which this motor asserrbly is to be fitted. The bearing block comprises two parts, a first part fixed to the stator and a second part fixed to the rotor. The bearing block is fixed to a central portion 253 of the wall of the stator 252 and also to a central portion 225 of the housing wall 220 of the rotor 240. The rotor 240 is thus rotationally fixed to the vehicle with which it is to be used via the bearing block 223 at the central portion 225 of the rotor 240. This has an advantage in that a wheel rim and tyre can then be fixed to the rotor 240 at the central portion 225 using the normal wheel bolts to fix the wheel rim to the central portion of the rotor and consequently firmly onto the rotatable side of the bearing block 223. The wheel bolts may be fitted through the central portion 225 of the rotor through into the bearing block itself. With both the rotor 240 and the wheel being mounted to the bearing block 223 there is a one to one correspondence between the angle of rotation of the rotor and the wheel.

Figure 3 shows an exploded view of the same motor assembly illustrated in Figure 2 from the opposite side. The rotor 240 comprises the outer rotor wall 220 and circumferential wall 221 within which magnets 242 are circumferentially arranged. As previously described, the stator 252 is connected to the rotor 240 via the bearing block at the central portions of the rotor and stator walls.

A V shaped seal is provided between the circumferential wall 221 of the rotor and the outer edge of the stator.

The rotor also inoludes a set of magnets 227 for position sensing, otherwise known as commutation magnets, which in conjunction with sensors mounted on the stator allows for a rotor flux angle to be estimated. The rotor flux angle defines the positional relationship of the drive magnets to the coil windings. Alternatively, in place of a set of separate magnets the rotor may include a ring of magnetic material that has multiple poles that act as a set of separate magnets.

To allow the commutation magnets to be used to calculate a rotor flux angle, preferably each drive magnet has an associated commutation magnet, where the rotor flux angle is derived from the flux angle associated with the set of commutation magnets by calibrating the measured commutation magnet flux angle. To simplify the correlation between the commutation magnet flux angle and the rotor flux angle, preferably the set of commutation magnets has the same number of magnets or magnet pole pairs as the set of drive magnet pairs, where the commutation magnets and associated drive magnets are approximately radially aligned with each other. Accordingly, for the purposes of the present embodiment the set of commutation magnets has 32 magnet pairs, where each magnet pair is approximately radially aligned with a respective drive magnet pair.

A sensor, which in this embodiment is a Hall sensor, is mounted on the stator. The sensor is positioned so that as the rotor rotates each of the commutation magnets that form the commutation magnet ring respectively rotates past the sensor.

As the rotor rotates relative to the stator the commutation magnets correspondingly rotate past the sensor with the Hall sensor outputting an AC voltage signal, where the sensor outputs a complete voltage cycle of 360 electrical degrees for each magnet pair that passes the sensor.

For improved position detection, preferably the sensor includes an associated second sensor placed 90 electrical degrees displaced from the first sensor.

In the present embodiment the electric motor includes four coil sets 60 with each coil set 60 having three coil sub-sets that are coupled in a wye configuration to form a three phase sub-motor, resulting in the motor having four three phase sub-motors. The operation of the respective sub-motors is controlled via one of two control devices 400, as described below. However, although the present embodiment describes an electric motor having four coil sets 60 (i.e. four sub motors) the motor may equally have one or more coil sets with associated control devices. In a preferred embodiment the motor 40 includes eight coil sets 60 with each coil set 60 having three coil sub-sets that are coupled in a wye configuration to form a three phase sub-motor, resulting in the motor having eight three phase sub-motors.

Similarly, each coil set may have any number of coil sub-sets, thereby allowing each sub-motor to have two or more phases.

Figure 4 illustrates the connections between the respective coil sets 60 and the control devices 400, where a respective coil set 60 is connected to a respective three phase inverter 410 included on a control device 400. As is well known to a person skilled in the art, a three phase inverter contains six switches, where a three phase alternating voltage may be generated by the controlled operation of the six switches. However, the number of switohes will depend upon the number of voltage phases to be applied to the respective sub motors, where the sub motors can be constructed to have any number of phases. Each control device 400 is arranged to communicate with the other control device 400 via a communication bus.

Preferably, the control devices 400 are of a modular construction. Figures 5 and 6 illustrate exploded views of a preferred embodiment, where each control device 400, otherwise known as a power module, includes a power printed circuit board 500 on which is mounted a control printed circuit board 520, four power source busbars 530 for connecting to a DC battery via the DC link capacitor, six phase winding busbars 540 for connecting to respective coil windings, and two power substrate assemblies 510, where each power substrate assembly 510 includes an inverter.

Two of the four power source busbars 530 and three of the six phase winding busbars 540 are encapsulated in a first plastic housing to form a first lead frame 560, with the remaining power source busbars 530 and phase winding busbars 540 being encapsulated in a second plastic housing to form a second lead frame 560, as described below. The first and second lead frames 560 allow the respective inverters to be electrically coupled to the DC busbar and coil windings. Any suitable method for encapsulating the respective power source busbars and phase winding busbars within a respective plastic housing may be used, for example using injection moulding techniques.

-10 -Each of the control device components are mounted within a control device housing 550 with, as illustrated in Figure 6, the power source busbars 530 being formed in a section of the respective lead frames 560 opposite to a section of the lead frame to which the phase winding busbars 540 are formed in.

The pair of power source busbars 530, which form part of the first lead frame, are for providing a current source to a first inverter formed on one of the power substrates assemblies 510. The second pair of power source busbars 530, which form part of the second lead frame, are for providing a current source to a second inverter formed on the second power substrate assembly 510.

The power printed circuit board 500 includes a variety of other components that include drivers for the inverter switches formed on the power substrate assemblies 510, where the drivers are used to convert control signals from the control printed circuit board 520 into a suitable form for operating switches mounted on the power printed circuit board 500, however these components will not be discussed in any further detail.

The respective lead frames 560 are arranged to be mounted on the power printed circuit board 500, with each lead frame 560 being arranged to be mounted over a respective power substrate assembly 510 mounted on the power printed circuit board 500. Each lead frame 560 includes an aperture arranged to extend around inverter switches formed on a respective power substrate assembly 510. Figure 12 illustrates a preferred embodiment of a power substrate assembly 510 -11 -having six inverter switches arranged in pairs to form three inverter legs.

The lead frame 560 also acts as a spacer for separating the control printed circuit board 520 from the power printed circuit board 500 when both the power printed circuit board 500 and the control printed circuit board 520 are mounted in the control module housing 550.

Figure 7 provides a perspective view of a lead frame 560, where two power source busbars 530 and three phase winding busbars 540 are encapsulated within a plastic housing.

Each of the power source busbars 530, which form part of the first and second lead frames respectively, are formed from a single, continuous electrical conductor, where as stated above, two of the power source busbars 530 are encapsulated in the plastic housing of the first lead frame 560 and two of the power source busbars 530 are encapsulated in the plastic housing of the second lead frame 560. The power source busbars 530 may be manufactured by any suitable means, for example stamping, machined or casting.

By way of illustration, a transparent perspective view of a lead frame 560 is shown in Figure 8, where the electrically conducting elements that form the respective power source busbars 530 include a first section 800 arranged to extend from the plastic housing 850 for coupling an inverter to the electrically conducting element, a second section 810 arranged to extend from the plastic housing 850 for coupling the power supply to the electrically conducting element, and a third section 820 encapsulated within the plastic housing 850 positioned between the first section 800 of the -12 -electrically conducting element aud the secoud section 810 of the electrically conducting element.

As shown in Figure 8 for each lead frame 560, the first section 800 of both lead frame power souroe busbars 530 extend from the lead frame's plastic housing 850, with a portion of the first section 800 of the first power source busbar 530 being located in a first plane and the first section 800 of the second power source busbar 530 being located in a second plane. When mounted within the control device housing 550, both these sections of the power source busbars are formed above the plane of the power circuit board 500. Preferably, the portion of the power source busbars in the first plane and second plane respectively are arranged to be substantially co-planar and arranged to be coupled to legs of the inverter, with one of the power source busbars 530 acting as the positive power rail and the other power source busbar 530 acting as the negative power rail, as is well known to a person skilled in the art.

The second sections 810 of each of the power source busbars 530 extend from the lead frame's plastic housing 850 and include a coupling section for coupling the respective power source busbars 530 to the DC power source, which in this embodiment is via the DC link capacitor. The second section 810 of one of the power source busbars 530 is connected to the positive power rail and the second section of the other power source busbar is connected to the negative power rail of the DC power source.

To isolate a fault associated with one or more of the inverters mounted within the control devices 400, which may oause a current overload condition, at least one of the power source busbars 530 for each of the respective lead -13 -frames 560, is arranged to electrically isolate the DC power source from the inverter should the current load to the inverter exoeeds a predetermined current load.

To allow the DC power source to be electrically isolated from a faulty inverter, the third section 820 of one of the power source busbars 530, formed within the plastic housing 850 of a lead frame 560, is arranged to have a portion designed to have a reduced current load capacity relative to the rest of the third section 820 and the first and second section of the power source busbar 530. For the purposes of the present embodiment, the portion of the third section 820 having a reduced current load capacity is arranged to melt at a predetermined current load, thereby causing the first section 800 of the power source busbar 530 to become electrically isolated from the second section 810 of the power source busbar 530 upon the predetermined current load being exceeded.

Preferably, the electrical characteristics of the portion of the third section 820 having reduced current load capacity is designed to ensure that for current loads below the predetermined current load, any heat generated by current flow it the power source busbar 530 would be insufficient to melt the plastic housing within which the power source busbar 530 is encapsulated.

Although the present embodiment describes all of the third section of the power source busbar 530 being encapsulated in a plastic housing 850, in an alternative embodiment the plastic housing 850 may have a gap/section removed to allow the portion of the third section 820 having the reduced current load capacity to be visually inspected, thereby allowing someone to visually determine whether the first -14 -section 800 of the power source busbar 530 has become electrically isolated from the second section 810.

Preferably, physical characteristics/parameters of the portion of the third section 820 of the power scurce busbar 530 that has the reduced current load capacity are chosen so that the connection between the first section 800 and the second section 810 of the power source busbar 530 is arranged to melt at the predetermined current load. Examples of the physical parameters that may be selected include, the type of material the power source busbar 530 is made of, and the area and length of the relevant portion of the power source busbar 530.

By way of illustration, Figure 9 represents an example of a power source busbar 530 prior to encapsulation within a plastic housing. As illustrated in Figure 9, the section 820 (i.e. the third section) of the power source busbar 530 positioned between the portion 810 (i.e. the second section) of the busbar arranged to be coupled to the positive or negative power rail of the DC power source and the planar section 800 (i.e. the first section) for coupling to the inverter, includes a portion that has reduced cross sectional area relative to the rest of the power source busbar, where the metal and dimensional characteristics are selected to melt at a predetermined current load, for example 50 Amps, thereby electrically isolating the first section 800 from the second section 810 of the power source busbar 530.

Amy suitable mechanism may be used for determining the reguired characteristics of the third section 820 to allow it to melt at a predetermined current load, for example trial and error and/or software modelling.

-15 -To further aid illustration of the power source busbar configuration, Figure 10 illustrates the respective positions of the two lead frame power source busbars 530 with the lead frame's plastic housing having been removed.

As shown, in accordance with the description, a portion of the first section 800 of the first power source busbar 530 is located in a first plane with the first section 800 of the second power source busbar 530 being located in a second plane, where the portion of the power source busbars 530 in the first plane and second plane respectively are arranged to be substantially co-planar. The second section 810 of each of the power source busbars 530 include a coupling section for coupling the respective power source busbars 530 to the DC power source, where the second section 810 of one of the power source busbars 530 is connected to the positive power rail and the second section 810 of the other power source busbar 530 is connected to the negative power rail of the DC power source. The third section 820 for one of the power source busbars 530 has a portion that has a reduced cross section that is arranged to melt at a predetermine current load, thereby electrically isolating the first section 800 of the power source busbar 530 from the second section 810.

The six phase winding busbars 540 formed in the respective lead frames 560, and placed on the opposite side of the respective power substrate assemblies 510 to the power source busbars, are arranged to be coupled to a respective inverter leg for coupling to a respective coil winding, as is well known to a person skilled in the art (i.e. a first set of phase winding busbars 540 are coupled to each leg of the three phase inverter formed on one of the power substrate assemblies 510 and a second set of phase winding -16 -busbars 540 are coupled to each leg of the three phase inverter formed on the other power substrate assembly 510) As illustrated in Figure 8, each of the phase winding busbars 540, which form part of the first and second lead frames 560 respectively, are formed from a single, continuous electrical conductor, which are also encapsulated in the lead frames plastic housing 850. Each of the electrically conducting elements, which form the phase winding busbars 540, includes a first section 900 extending from the plastic housing 850 for coupling the inverter to the electrically conducting element, a second section 910 extending from the plastic housing 850 for coupling to a respective coil winding, and a third section 930 encapsulated within the plastic housing 850 positioned between the first section 900 of the electrically conducting element and the second section 910 of the electrically conducting element for electrically coupling the first section 900 and second section 910 of the electrically conducting element.

By way of illustration, Figure 13 shows a preferred embodiment of the inverter switches being electrically connected to the power source busbar 530 to phase winding busbars via an electrical connector 871.

In particular, the second section 910 of each of the phase winding busbars 540 include a coupling section for coupling the phase winding busbar 540 to a phase winding of one of the coil sets, as described below.

Once the lead frames 560 have been mounted on the power printed circuit board 500, the control printed circuit board -17 - 520 is arranged to be mounted in the control module honsing 550 above the power printed circuit board 500.

The control printed circuit board 520 includes a processor for controlling the operation of the inverter switches.

Additionally, each control printed circuit board 520 includes an interface arrangement to allow communication between the respective control devices 400 via a communication bus with one control device 400 being arranged to communicate with & vehicle controller mounted external to the electric motor. The processor 420 on each control device 400 is arranged to handle communication over the interface arrangement.

The processors 420 on the respective control devices 400 are arranged to control the operation of the inverter switches mounted on the respective power substrates 520 within the control housing 550 to allow each of the electric motor coil sets 60 to be supplied with a three phase voltage supply, thereby allowing the respective coil sub-sets 61, 62, 63 to generate a rotating magnetic field. As stated above, although the present embodiment describes each coil set 60 as having three coil sub-sets, the present invention is not limited by this and it would be appreciated that each coil set 60 may have one or more coil sub-sets.

Under the control of the respective processors 420, each three phase bridge inverter 410 is arranged to provide PWM voltage control across the respective coil sub-sets, thereby generating a current flow in the respective coil sub-sets for providing a reguired torque by the respective sub-motors.

-18 -PNM control works by using the notor inductance to average out an applied pulse voltage to drive the required current into the motor coils. Using FWM control an applied voltage is switched across the motor windings. During the period when voltage is switched across the motor coils, the current rises in the motor coils at a rate dictated by their inductance and the applied voltage. The PWM voltage control is switched off before the current has increased beyond a required value, thereby allowing precise control of the current to be achieved.

For a given coil set 60 the three phase bridge inverter 410 switches are arranged to apply a single voltage phase across each of the coil sub-sets. :is

Using PWN switching, the plurality of switches are arranged to apply an alternating voltage across the respective coil sub-sets. The voltage envelope and phase angle of the electrical signals is determined by the modulating voltage pulses.

The inverter switches can include semiconductor devices such as MOSFETs or IGBTs. In the present example, the switches comprise IGHTs. However, any suitable known switching circuit can be employed for controlling the current. One well known example of such a switching circuit is the three phase bridge circuit having six switches configured to drive a three phase electric motor. The six switches are configured as three parallel sets of two switches, where each pair of switches is placed in series and form a leg of the three phase bridge circuit. A single phase inverter will have two pairs of switches arranged in series to form two legs of an inverter.

-19 -The respective coils of the four coil sets are wound on individual stator teeth, which form part of the stator. The end portions 501 of the coil windings protrude through the planar rear portion 502 of the stator heat sink, as illustrated in Figure 6. Figure 6 illustrates a partial perspective view of the stator, where the end portions 501 of the coil windings for two of the four coil sets 60 extend away from the planar portion of the stator heat sink 253.

The control modules 400 are positioned adjacent to the planar portion of the stator heat sink 253, for mounting to the planar portion of the stator heat sink 253. For illustration purposes, a view of a single control module 400 separated from the stator heat sink 253 is shown in Figure 6.

For the purposes of the present embodiment, the planar portion of the heat sink 253 is located on the side of the stator that is intended to be mounted to a vehicle.

Preferably, to facilitate the mounting of the respective control modules 400 to the stator heat sink 253, the end sections 501 of the coil windings for the respective coil sets are arranged to extend away from the heat sink portion of the stator in substantially a perpendicular direction relative to the surface of the heat sink portion of the stator.

Preferably, mounted on the underside of the power printed circuit board 500, adjacent to the copper base plate of the power substrate assemblies 510, are six Hall sensors (not shown) for measuring the current in the respective coil windings associated with two of the four coil sets. The Hall -20 -sensor readings are provided to the control printed circuit board 520.

To allow the respective coil windings for two of the four coil sets 60 to be coupled to a respective phase winding busbar within a control module housing 550, as described above, the control module housing 550 is arranged to have six apertures 610.

The six apertures 610 are formed on an outer edge of the control module housing 550 on the side of the housing 550 that is to be mounted adjacent to the planar portion of the stator heat sink 253.

The size and position of the six apertures 610 formed in the control module housing 550 are arranged to match the positions and diameters of the end portions of the coil windings that extend from the planar portion of the stator heat sink 253, thereby allowing the respective end portions of the coil windings to extend through the apertures 610 when the control housing module 550 is mounted on to the planar portion of the stator heat sink 253.

Once the power printed circuit board 500 has been lowered into position in the control module housing the lead frames 560 are positioned over a respective power substrate assembly with the respective inverter formed on the power substrates being coupled to the respective power source busbars and phase winding busbars, as described above.

As stated above, each of the phase winding busbars 540 formed on the respective lead frames 560 are arranged to include a coupling section for coupling the phase winding busbar to a phase winding of one of the coil sets. The -21 -coupling section for each phase winding busbar is arranged to extend around a respective aperture 610 formed in the base of the control module housing 550.

The control module may be mounted to the stator by any suitable means, for example one or more bolts that extend through the control module into the surface of the stator heat sink.

Once the control module has been mounted to the stator, the respective coupling sections of the phase winding busbars 540 mounted on the power printed circuit board 500 are coupled to a respective end section of a coil winding, where any suitable means may be used to couple the coupling section of the phase winding busbar 540 to a respective end section of a coil winding, for example crimping or welding, and the power source busbars are coupled to the positive and negative power rails respectively.

The inverter formed on one power assembly 510, which is coupled via the respective phase winding busbars to a first coil set 60, is arranged to control current in the first coil set. The other inverter formed on the other power assembly 510 in the control module 400 is arranged to control current in a second coil set 60, where the current measurements made by the respective current sensors are used by the processor on the control printed circuit board 520 to control current in the respective coil sets 60.

Similarly, the second control module 400 is arranged to control current in a third and fourth coil set 60.

-22 -

Claims

CLAIMS1. A lead frame for coupling an inverter to both a DC power supply and to a coil winding for an electric motor or generator, the lead frame comprising a first electrically conducting element that is formed from a single, continuous conductor and encapsulated in a plastic housing, and a second electrically conducting element encapsulated in the plastic housing, wherein the first electrically conducting element includes a first section extending from the plastic housing for coupling the inverter to the first electrically conducting element, a second section extending from the plastic housing for coupling the power supply to the first electrically conducting element, and a third section encapsulated within the plastic housing positioned between the first section of the first electrically conducting element and the second section of the first electrically conducting element, wherein the third section of the first electrically conducting element includes a region arranged to electrically isolate the first section from the second section at a substantially predetermined current load, wherein the second electrically conducting element includes a first section extending from the plastic housing for coupling the inverter to the second electrically conducting element and a second section extending from the plastic housing for coupling the coil winding to the second electrically conducting element.
2. A lead frame according to claim 1, wherein the plastic housing is arranged to extend around the lnverter.
3. A lead frame according to claim 1 or 2, wherein the first electrically conducting element is encapsulated in the -23 -plastic housing on the opposite side of the plastic housing to the second electrically conducting element.
4. A lead frame according to any one of the preceding claim, wherein a portion of the third section of the first electrically conducting element is visible through the plastic housing.
5. A lead frame according to any one of the preceding ]0 claims, wherein the region of the third section of the first electrically conducting element arranged to electrically isolate the first section from the second section at the predetermined current load is visible through the plastic housing. :is
6. A lead frame according to any one of the preceding claims, wherein the first electrically conducting element is made from copper.
7. A lead frame according to any one of the preceding claims, wherein the portion of the third section of the first electrically conducting element arranged to electrically isolate the first section from the second section at a predetermined current load is arranged to melt at the predetermined current load.
8. A lead frame according to any one of the preceding claims, further comprising a third electrically conducting element, wherein the third electrically conducting element includes a first section extending from the plastic housing for coupling the inverter to the first electrically conducting element, a second section extending from the plastic housing for coupling the power supply to the first electrically conducting element, and a third section -24 -encapsulated within the plastic housing positioned between the first section of the first electrically conducting element and the second section of the first electrically conducting element.
9. A lead frame according to claim 8, wherein the first electrically conducting element is arranged to be coupled to a positive power rail and the third electrically conducting element is arranged to be coupled to a negative power rail. :io
10. A lead frame according to any one of the preceding claims, further comprising a fourth electrically conducting element having a first section extending from the plastic housing for coupling the inverter to the fourth electrically conducting element and a second section extending from the plastic housing for coupling the coil winding to the fourth electrically conducting element, and a fifth electrically conducting element having a first section extending from the plastic housing for coupling the inverter to the fifth electrically conducting element and a second section extending from the plastic housing for coupling the coil winding to the fifth electrically conducting element.
11. A lead frame according to claim 10, wherein the second, fourth and fifth electrically conducting elements are arranged to be coupled to a respective coil winding.
12. A lead frame according to any one of the preceding claims, wherein the first and second electrically conducting elements are encapsulated in the plastic housing on an opposite side of the plastic housing to the second, fourth and fifth electrically conducting elements.

-25 -
13. A control module for an electric motor, having a plurality of lead frames according to any one of the preceding claims.
14. Mi electric motor having a plurality of control modules according to claim 13.-26 -