Patent Publication Number: US-11643221-B2

Title: Starting/generating system and method for an aircraft turbine engine

Description:
TECHNICAL FIELD 
     The present invention relates to the field of aeronautics and, more particularly, a starting/generating system for an aircraft turbine engine that is configured, on the one hand, to start a turbine engine and on the other hand to electrically power an on-board electrical network once the turbine engine is started. 
     A starting/generating system comprises in a known manner a drive motor to start the turbine engine. In the prior art, as indicated in patent application WO2017/068274 of the applicant, a brushless drive motor was generally used. In order to reduce maintenance costs and to increase reliability, it is now preferred to use a brushless drive motor/generator. 
     In a known manner, in reference to  FIG.  1   , the starting/generating system includes a brushless drive motor/generator  1  that is mounted in the vicinity of the turbine engine in a non-pressurised zone NP, in particular, in a housing  3  of a nacelle of the aircraft. The brushless drive motor/generator  1  is connected to a management device  2 , housed in a pressurised zone P of an aircraft, in particular in an avionics bay  5 . 
     The management device  2  comprises, on the one hand, a control module  2   a  connected to the brushless drive motor/generator  1  by a control cable L 1  and, on the other hand, a power module  2   b  connected to the brushless drive motor/generator  1  by a power cable L 2 . 
     The control module  2   a  is configured to supply a control signal to the brushless drive motor/generator  1  via the control cable L 1 . The control signal corresponds for example to a direct current, called excitation current, making it possible to control during the starting the torque or the rotation speed. During the generating, the control signal makes it possible to control the voltage supplied by the brushless drive motor/generator  1 . The power module  2   b  is connected to the on-board electrical network  4  and is configured to supply electrical power to the brushless drive motor/generator  1  to ensure the starting of the turbine engine. In generation, once the turbine engine started, the power module  2   b  receives electrical power from the brushless drive motor/generator  1  that it distributes to the on-board electrical network  4 . In practice, the on-board electrical network  4  has a high voltage, in particular, of about 115 VAC. The control module  2   a  moreover makes it possible to control the electronics of the power module  2   b . The management device  2  and the brushless drive motor/generator  1  each have a heavy structure and dissipate heat. Also, they each have dedicated means of cooling (not shown). 
     In reference to  FIG.  1   , the control cable L 1  and the power cable L 2  must be spaced apart from one another by a safety distance D, for example of about 10 cm, in order to prevent the power cable L 2  from disturbing the control signal transmitted by the control cable L 1 , in particular, electromagnetically due to the intensity of the current circulating in the power cable L 2 , and the chopping principle used by the power module  2   b  generating disturbances linked to the quick variations in the chopped voltages. The positioning of the control cable L 1  with respect to the power cable L 2  is a constraint during the installation of the starting/generating system. In addition, it is necessary to provide shielding members in order limit electromagnetic disturbances. 
     In addition to this disadvantage, the power cable L 2  has a length of several metres and thus has an intrinsic electrical resistance that results in a loss of power transmitted by the power cable L 2 . This intrinsic electrical resistance is all the more restrictive when the objective is to use an on-board electrical network  4  having a low voltage, in particular of about 28V. In other words, to supply a power equivalent to an on-board electrical network  4  of the 115 VAC type, it is necessary to circulate a current that has a high intensity. Thus, any intrinsic electrical resistance of the power cable L 2  results in an increase in the heat generated by the Joule effect as well as a substantial drop in the power transmitted. 
     In order to eliminate this disadvantage, a solution would be to house the starting/generating system entirely in the housing  3  of the turbine engine, i.e. in a non-pressurised zone NP as shown in  FIG.  2   . For this purpose, the management device  2  is positioned adjacent to the brushless drive motor/generator  1 . As the control module  2   a  and the power module  2   b  are in the vicinity of the brushless drive motor/generator  1 , it is no longer necessary to have recourse to a power cable L 2  of great length as in the prior art, which reduced the electrical losses. This solution however has the disadvantage of exposing the management device  2  to conditions of pressure, temperature and mechanical vibrations that render its design very difficult. 
     The invention therefore has for purpose to overcome these disadvantages by proposing a new starting/generating system that makes it possible, on the one hand, to limit positioning constraints between the cables and, on the other hand, to limit the losses of power while allowing for optimal operation. 
     SUMMARY 
     For this purpose, the invention relates to a starting/generating system for an aircraft turbine engine, the starting/generating system comprising at least one brushless drive motor/generator, at least one control module and at least one power module, the brushless drive motor/generator being configured to be positioned in a housing in a non-pressurised zone to start an aircraft turbine engine, the power module being configured to be connected to an on-board electrical network of the aircraft, the power module being configured to supply/receive electric power from the brushless drive motor/generator, the control module being connected to the brushless drive motor/generator by a control cable in order to control its operation. 
     The invention is remarkable in that the power module is configured to be mounted in the housing of the non-pressurised zone so as to be located adjacent to the brushless drive motor/generator and in that the control module is configured to be mounted in a pressurised zone of the aircraft, the control module being connected to the power module by a two-way communication cable in order to control its operation. 
     Thanks to the invention, a long power cable is no longer necessary given that the power module is located adjacent to the brushless drive motor/generator. This advantageously makes it possible to prevent any heating via the Joule effect or loss of power. In addition, this makes it possible to prevent any disturbance of the control cable by the power cable. Moreover, as the control module is offset from the turbine engine, the latter is not affected by the conditions of pressure and temperature, which guarantees an easier design and more reliable operation. Finally, a two-way communication makes it possible to carry out a precise control of the power module by the control module, which is particularly advantageous with a brushless drive motor/generator during the starting and generating phases. Furthermore, a two-way communication cable can be placed without substantial constraint with respect to the control cable, which accelerates the installation and the maintenance of a starting/generating system. 
     Preferably, the housing is metal in such a way as to form a Faraday cage which prevents the emission of electromagnetic disturbances to the outside, in particular, able to affect the control cable. 
     Preferably, the control module and the power module are configured to exchange digitally via the two-way communication cable. A digital communication allows for a substantial speed for reactive control. Furthermore, the shielding constraints of digital communication result in a mass that is much less than those required to shield a power cable. 
     Preferably, the power module comprising at least one inverter-rectifier comprising transistors, the control module comprises a calculation device configured to calculate control duty cycles of the transistors of the inverter-rectifier. Such a calculation device makes it possible to configure the power module reactively, in particular during the starting and generating phases, via the two-way communication cable. Alternatively, the calculation device is configured to calculate a current setpoint in starting mode associated with a local synchronous rectification. 
     According to a preferred aspect, the power module comprises at least one device for measuring one or more of the following parameters of the brushless drive motor/generator: direct voltage in interface with the on-board electrical network, phase current, control signal, speed of a rotor, angular position of a rotor, temperature. Such measurements make it possible to precisely follow the parameters of the starting/generating and allow for a reactive control to carry out an optimum starting/generating. 
     Preferably, the calculation device is configured to calculate the control duty cycles of the transistors of the inverter-rectifier according to one or more parameters measured by the measuring device. Thus, the controlling of the power module makes it possible to take account of the state of the brushless drive motor/generator in order to control it suitably. 
     According to a preferred aspect, the on-board electrical network is of the 28 VDC type. 
     According to an embodiment, the starting system comprises at least one cooling module, mounted in the housing, configured to cool the brushless drive motor/generator and the power module. Such a cooling module is advantageously shared between the brushless drive motor/generator and the power module, which makes it possible to limit its dimensions and therefore the size. Advantageously, as the control module does not dissipate substantial heat, it is not necessary to provide a cooling module in the pressurised zone. 
     The invention also relates to an aircraft comprising at least one turbine engine, at least one starting/generating system such as presented hereinabove, at least one pressurised zone and at least one non-pressurised zone. The control module of the starting/generating system is mounted in the pressurised zone while the power module and the brushless drive motor/generator of the starting/generating system are mounted in a non-pressurised zone. 
     Thanks to the invention, the control module remains housed in a pressurised zone (and tempered), which makes the design thereof easier and makes it more reliable. The power module and the brushless drive motor/generator of the starting/generating system are mounted together in a non-pressurised zone so as to limit power losses as mentioned hereinabove. 
     The invention further relates to a method for starting an aircraft turbine engine by means of a starting/generating system such as presented hereinabove, method in which:
         The control module emits starting instructions to the power module via the two-way communication cable, so that it powers the brushless drive motor/generator from the on-board electrical network and   The control module emits a control signal to the brushless drive motor/generator via the control cable in order to control the torque and/or the drive speed of the brushless drive motor/generator.       

     Such a method for starting allows for a starting of the turbine engine that is reliable and that limits the electrical losses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood when reading the following description, given solely by way of example, and in reference to the accompanying drawings wherein: 
         FIG.  1    diagrammatically shows a starting/generating system according to the prior art, 
         FIG.  2    diagrammatically shows a proposition of a new starting/generating system, 
         FIG.  3    diagrammatically shows a starting/generating system according to the invention and 
         FIG.  4    diagrammatically shown in detail a starting/generating system according to the invention. 
     
    
    
     Note that the figures disclose the invention in a detailed manner to implement the invention, said figures of course can be used to better define the invention where applicable. 
     DETAILED DESCRIPTION 
     In reference to  FIG.  3   , a starting/generating system for an aircraft turbine engine is shown according to an embodiment of the invention. The starting/generating system comprises a brushless drive motor/generator  1 , a control module  6  and a power module  7 . 
     In reference to  FIG.  3   , the power module  7  is mounted in a non-pressurised zone NP of the aircraft, adjacent to the brushless drive motor/generator  1 . The control module  6  is mounted in a pressurised zone P of the aircraft, at a distance from the power module  7  mounted in a non-pressurised zone NP. The control module  6  is connected to the power module  7  by a two-way communication cable L 3  in order to control its operation. 
     The invention shall be presented for an aircraft turbine engine, in particular an aircraft turbojet, but it goes without saying that the invention also applies to a helicopter turbine engine. 
     The brushless drive motor/generator  1  is configured to start the turbine engine. It comprises in a known manner a stator portion (stator) and a rotor portion (rotor) rotatably mounted with respect to the stator portion. The rotor portion is connected to a shaft of the turbine engine so as to allow for the driving thereof during the starting, the rotor portion being driven by the shaft of the turbine engine during the generating of current following the starting of the turbine engine. 
     The power module  7  is connected to an on-board electrical network  4 , in particular, a low-voltage electrical network. Preferably, the on-board electrical network  4  is of the 28 VDC type. The power module  7  is configured to supply electrical power to the brushless drive motor/generator  1  during the starting from the electrical power supplied by the on-board electrical network  4 . During the starting, the on-board electrical network  4  is electrically powered by an auxiliary source. Following the starting, during the generating, the power module  7  is configured to supply the electrical power to the on-board electrical network  4  from the electrical power supplied by the brushless drive motor/generator  1 . In other words, following the starting, the on-board electrical network  4  is electrically powered by the turbine engine. 
     As shown in  FIG.  4   , the power module  7  comprises electronic components so as to electrically power and receive the electrical power from the brushless drive motor/generator  1 . In particular, the power module  7  comprises at least one inverter-rectifier  71  which comprises, preferably, a plurality of controllable transistors. In this example, the power module  7  comprises at least one device for measuring 72 one or more of the following parameters of the brushless drive motor/generator  1 : direct voltage in interface with the on-board electrical network  4 , phase current, control signal, speed of a rotor, angular position of a rotor, temperature. 
     Preferably, the power module  7  and the brushless drive motor/generator  1  are separated by less than 10 cm, which limits any loss of power linked to the cabling. Preferably, the power module  7  and the brushless drive motor/generator  1  are connected together directly. 
     In reference to  FIG.  3   , the power module  7  and the brushless drive motor/generator  1  are housed in the same housing  3  in an aircraft nacelle so as to limit the size. Preferably, the housing  3  is metal so as to form a Faraday cage in order to favour electromagnetic confinement. 
     Optionally, the starting/generating system further comprises a cooling module  8  as shown in  FIGS.  3  and  4   . The cooling module  8  advantageously makes it possible to simultaneously cool the power module  7  and the brushless drive motor/generator  1  in a synergistic manner. Advantageously, the size of the cooling module  8  is substantially identical to the prior art and is mounted in the housing  3  of the nacelle. Advantageously, the control module  6  does not need to be cooled, as the starting/generating system comprises only one cooling module. 
     The control module  6  is configured to emit a control signal to the brushless drive motor/generator  1  in order to control its operation. In this example, in reference to  FIG.  3   , the control module  6  is connected to the brushless drive motor/generator  1  by a control cable L 1  similar to the prior art. In a known manner, the control signal makes it possible to control the torque and/or the rotation speed of the brushless drive motor/generator  1 . In practice, the control module  6  is connected to a calculator the aircraft from which it receives its instructions. 
     The control module  6  is also configured to control the operation of the power module  7 , in particular, during the starting and during the generating. In the prior art, the control module  6  was mounted directly to the power module  7 . According to the invention, the control module  6  is offset from the power module  7  and connected to the latter by a two-way communication cable L 3  in order to control its operation. Preferably, the two-way communication cable L 3  is of the BUS type and allows for digital communication between the control module  6  and the power module  7 . Contrary to a power cable L 2  according to the prior art, a two-way digital communication cable L 3  induces hardly any electromagnetic disturbances on the control cable L 1  (or any power losses). Also, the constraints for connecting the control module  6 , located in a pressurised zone P, to the power module  7  and to the brushless drive motor/generator  1 , located in a non-pressurised zone P, are eliminated given that the communication cable L 3  has no impact on the control signal transmitted by the control cable L 1 . 
     As shown in  FIG.  4   , the control module  6  comprises a device for generating a control signal  61  configured to emit a control signal on the control cable L 1  intended for the brushless drive motor/generator  1 . The control module  6  comprises a device for controlling the starting  62 , a device for controlling the generating  63  as well as a device for calculating  64  control duty cycles of the transistors of the inverter-rectifier  71  of the power module  7 . Thanks to the devices  62 ,  63 ,  64 , the control module  6  makes it possible to precisely control the power module  7 , which is particularly important for a brushless drive motor/generator  1  in comparison with a drive motor/generator with brushes according to the prior art. Preferably, the different functional devices  61 - 64  of the control module  6  belong to the same electronic card or to several electronic cards. Alternatively, the calculation device  64  is configured to calculate a current setpoint in starting mode associated with a local synchronous rectification. 
     Thanks to the two-way communication cable L 3 , the control module  6  and the power module  7  can exchange data to carry out an optimum starting or generating. For example, the power module  7  can transmit measurements taken by the measuring device  72  so that the calculation device  64  of the control module  6  calculates optimum control duty cycles of the transistors which are transmitted to the inverter-rectifier  71  of the power module  7 . 
     In this example, the starting/generating system is mounted in an aircraft. The aircraft comprises, on the one hand, a pressurised zone P, in particular an avionics bay  5  housed in the fuselage of the aircraft, and on the other hand, a non-pressurised zone NP, in particular, a turbine engine nacelle. The nacelle of a turbine engine is located in the immediate vicinity of the turbine engine in order to be able to start it. The nacelle comprises the housing  3  wherein the brushless drive motor/generator  1 , the power module  7  and the cooling module  8  are mounted. The control module  6  is housed in the avionics bay  5 . In this example, the pressurised zone P is an avionics bay  5  and the non-pressurised zone NP is a nacelle but it goes without saying that the zones could be different. 
     An example of an implementation of a method for starting shall now be presented. First of all, the control module  6  emits starting instructions to the inverter-rectifier of the power module  7  via the two-way communication cable L 3  so that it powers the brushless drive motor/generator  1  from the on-board electrical network  4 . The control module  6  also emits a control signal, generated by the generation device  61 , to the brushless drive motor/generator  1  via the control cable L 1  in order to control the torque and/or the drive speed of a shaft of the turbine engine in order to start it. 
     Preferably, the power module  7  takes measurements of parameters of the power module  7  and/or of the brushless drive motor/generator  1  and transmits the parameter or parameters measured to the control module  6  so that the latter adapts the control instructions sent to the inverter-rectifier. Preferably, the calculation device  64  of the control module  6  calculates the optimised control duty cycles of the transistors of the inverter-rectifier  71  from the parameters obtained by the measuring device  72 .