MOTOR WITH TRANSIENT VOLTAGE SUPPRESSION

Abstract

An electric motor includes: a stator; a rotor; and a printed circuit board, pcb, mounted to an end of the motor, the motor end windings being provided as connections on the pcb. The motor further includes transient voltage suppression, TVS, components on the pcb.

Claims

1. An electric motor comprising: a stator; a rotor; and a printed circuit board, pcb, mounted to an end of the motor, the motor end windings being provided as connections on the pcb; the motor further comprising transient voltage suppression (TVS) components on the pcb.

2. An electric motor as claimed in claim 1, wherein the pcb is a heavy copper pcb.

3. An electric motor as claimed in claim 1, wherein the pcb has multiple layers.

4. An electric motor as claimed in claim 1, wherein the motor is a three-phase motor, and wherein the motor further includes: three TVS components, each TVS component connected between a respective phase line and earth.

5. An electric motor as claimed in claim 1, wherein the motor is a three-phase motor, and wherein the motor further includes: three TVS components, each TVS component connected as a shunt across a respective phase line.

6. An electric motor as claimed in claim 1, wherein the motor an aircraft engine.

7. An electric motor as claimed in claim 1, wherein the TVS components are arranged to provide lightning strike protection.

8. A motor and motor drive assembly comprising: a motor drive; and an electric motor as claimed in claim 1, wherein the motor drive is connected to the electric motor via cables.

9. A method of protecting an electric motor from transient voltage suppression, the method comprising: providing transient voltage suppression components on a printed circuit board; providing end winding structures on the printed circuit board; and connecting the printed circuit board at the end of the electric motor.

Description

BRIEF DESCRIPTION

[0012] Examples according to the disclosure will now be described with reference to the drawings. These are by way of example only and variations are possible within the scope of the claims.

[0013] FIG. 1 shows a motor with an end winding PCB according to the disclosure.

[0014] FIG. 2 shows a circuit diagram of one possible embodiment according to the disclosure.

[0015] FIG. 3 shows a circuit diagram of another possible embodiment according to the disclosure.

DETAILED DESCRIPTION

[0016] As is known, electric motors include a rotor and a stator, conductive coils and magnets, to generate electrical energy. Such motors are well known and will not be described in detail. Connections have to be made between the various windings in the motor as well as connections between the motor parts and external systems.

[0017] Many motors use multi-strand wire bundles to form the conductors for the windings so as to minimise eddy currents. It is difficult to connect such windings to each other or to other components without negating the multi-strand effect and/or creating an increased resistance at the connection that results in increased losses.

[0018] In conventional motors, different windings are electrically connected to each other by physically overlapping the windings and/or by providing end-windings extending from the ends of the motor where conductors of different phases of the motor pass over the end-windings to form a connection with each other. The end-windings are large and it is, as mentioned above, difficult to provide the necessary electrical and magnetic isolation when the conductors physically overlap each other. Connecting the conductors to other components of the motor or of external systems often uses soldering or brazing which fuses the multi-strand wires together at the ends of the coils.

[0019] More recently, motors have been designed in which connections for such conductors either to each other or to other components are provided by means of a printed circuit board (PCB) 10 and, in particular, a heavy copper PCB. The heavy copper PCB allows for the segmentation of the copper into a number of layers, allowing the PCB to be used at high frequencies and for electrical isolation between the different windings since the windings do not need to physically overlap in order to be electrically connected. Using a PCB enables, for example, the windings to be segmented and electrically connected via PCB traces, which improves their use in high frequency operations.

[0020] Further, the PCB 10 can be designed such that a bundle of multi-strand wires can be terminated with a stud or a crimp at the ends of the wires, and the stud or crimp providing a phase terminal 20 physically attached to the PCB by means of the stud without the need to solder or braze the wires. This allows for quick assembly and provides a lower resistance path and a more reliable connection than a solder or braze. Particularly at higher temperatures, soldered or brazed connections can fatigue and present a higher resistance path. Other interconnect technologies can also be adopted, depending on the application e.g. a compliant pin.

[0021] The use of a PCB as an interconnecting mechanism for all connections provides consistency and ease of design and manufacture. A heavy copper PCB is able to carry higher currents without problems of isolation or losses. The use of a PCB instead of overlapping of magnet wire end-windings also results in a more compact motor design.

[0022] The inventors have realised that when a PCB is used as the end winding of the motor, additional circuitry could be provided on the PCB to provide additional functions at the motor, without the need to add to the overall size and weight of the motor. This allows functions to be moved from the motor drive to the motor.

[0023] In particular, lightning strike protection features can be moved from the motor drive, as is conventionally the case, to the motor end winding PCB. More specifically, transient volt suppression (TVS) components 40 are mounted to the PCB 10.

[0024] Circuit diagrams showing two possible implementations of the invention are shown in FIGS. 2 and 3.

[0025] FIG. 3 shows a possible arrangement for e.g. classical aircraft where common mode threat protection (e.g. lightning or other voltage surge protection) via the chassis can be provided. FIG. 2 shows the motor, or machine 100 which is connected to a motor drive 200 via cables (also called a harness) 300 for the phases of the motor. FIG. 2 shows a three phase motor represented by windings 50 to which the end winding PCB 10 is connected. A transient voltage suppression device 501, 502, 503 is connected to the PCB 10 between each phase and earth. Any suitable TVS device can be used.

[0026] For more modern aircraft, regulations prevent current being shunted through the chassis and so LSP can be provided using a differential mode topology such as shown in FIG. 3. The components are as described in relation to FIG. 2 except, rather than being earthed through the chassis, the TVS devices are connected as shunts across the phase lines.

[0027] Present industry standards may make it not yet feasible to use such an arrangement for aircraft, since, currently, any part of an aircraft that has a connector must be threat tested and each pin has to be struck, in testing, to simulate a lightning strike. Future developments in the aircraft industry, however, may make it more feasible to use such an arrangement for LSP in aircraft. The arrangement of the invention also, however, has other applications e.g. in the automotive industry.

[0028] The advantage of the invention is that functionality can be distributed to a line replaceable unit (LRU)— i.e. the end winding PCB which is, in any case, present and typically has additional unused space/volume that can be utilised.

[0029] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.