Abstract:
A socket system for the protection against lightening of an aircraft disposed between a connection terminal of the aircraft and an end connector of a generator set powered by a power supply cable having several electrical conductors includes an extension socket connected between the end connector and the connection terminal and a safety device including in a housing made of electrically insulating material, and clipping means designed to clip an electrical signal. The installation of such a safety device prevents the propagation of an electrical overvoltage beyond the safety device.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to a socket system for the protection against lightening of an aircraft powered with electricity by means of a generator set, and an ensemble comprising an aircraft, a generator set and such a socket system. 
       BACKGROUND OF THE INVENTION 
       [0002]      FIG. 1  shows an aircraft  10  which is immobile on the ground. The aircraft is powered with electricity by means of a generator set  20  via a power supply cable  30  which has several electrical conductors and is provided at its end with an end connector  40  having an electrical contact for each electrical conductor. 
         [0003]    In order to allow connection to the generator set  20 , the aircraft  10  has a connection terminal  50  having, for each electrical conductor, an electrical contact downstream of which a conductor  14  is connected embedded in the aircraft  10  and to which at least one electrical component  12  of the aircraft  10  is connected. 
         [0004]    The connection between the end connector  40  and the connection terminal  50  is performed by means of an extension socket  60 . 
         [0005]      FIG. 2  shows an example of an extension socket  60  comprising a body  61  with a first connector  62  comprising, for each electrical contact of the end connector  40 , an electrical contact which is connected electrically to the said electrical contact of the end connector  40 , and a second connector  64  comprising, for each electrical conductor, an electrical contact  65  (in this case female) which is electrically connected to the electrical contact of the first corresponding connector  62  and which is designed to be connected to an electrical contact (in this case male) of the connection terminal  50 . 
         [0006]    The extension socket  60  allows here the connection of six electrical conductors which are indicated here by the reference letters A, B, C, N, E and F. The connection terminal  50  thus comprises, for each electrical conductor A, B, C, N, E, F, an embedded conductor  14  which is electrically connected to an electrical conductor A, B, C, N, E, F via the second connector  64  and the connection terminal  50 . 
         [0007]    The extension socket  60  has a third connector  66  which, for each electrical conductor, has a female electrical contact  68  which is electrically connected to the electrical contact of the first connector  62  connected to the said electrical conductor and which allows for example the connection of a connecting member of a multimeter. 
         [0008]    The connection of the generator set  20  to the aircraft  10  forms a loop. 
         [0009]    When lightning strikes the ground close to the aircraft  10 , a part of the magnetic field induced by the lightning generates a voltage drop in the loop, creating an inductive coupling which generates an electrical overvoltage in the power supply cable  30 . This electrical overvoltage is propagated as far as the aircraft  10  with the risk of damaging certain electrical components  12  on-board the aircraft  10 . 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    An aspect of the present invention proposes a socket system for the protection against lightening of an aircraft which does not have the drawbacks of the prior art and which in particular prevents the propagation of an electrical overvoltage as far as the aircraft. 
         [0011]    Described herein is a socket system for the protection against lightening of an aircraft powered with electricity by means of a generator set thanks to a power supply cable comprising several electrical conductors and at the end of which is set an end connector having an electrical contact for each electrical conductor, the aircraft having a connection terminal having, for each electrical conductor, an electrical contact downstream of which is connected a conductor embedded in the aircraft and to which is connected at least one electrical component of the aircraft, the socket system comprising:
       an extension socket connected between the end connector and the connection terminal and comprising:   a first connector connected to the end connector and having, for each electrical conductor of the end connector, an electrical contact designed to be electrically connected to the said each electrical conductor of the end connector,   a second connector having, for each electrical contact of the first connector, an electrical contact which is electrically connected to the said electrical contact of the first connector and connected to an electrical contact of the connection terminal,   a third connector having, for each electrical contact of the first connector, a female electrical contact electrically connected to the said electrical contact of the first connector, and   a safety device comprising:   a housing made of electrically insulating material,   for each female electrical contact, a male electrical contact made of electrically conductive material, projecting from the housing and designed to be inserted in the said female electrical contact,   clipping means designed to clip an electrical signal,   a printed circuit seated inside the housing and having conductive tracks connecting the male electrical contacts and the clipping means.       
 
         [0021]    Such a socket system prevents the propagation of an electrical overvoltage as far as the aircraft by means of signal clipping. 
         [0022]    Advantageously, one of the conductors is the neutral conductor and clipping means are arranged between each male electrical contact corresponding to an electrical conductor other than neutral and the male electrical contact corresponding to neutral. 
         [0023]    Advantageously, each clipping means is an assembly consisting of a diode or several diodes mounted in series between the male electrical contact corresponding to each electrical conductor other than neutral and the male electrical contact corresponding to neutral. 
         [0024]    Advantageously, each diode has a transition time which is less than the time for which each electrical component to be protected may be exposed to an overvoltage without damage. 
         [0025]    According to a particular embodiment, when the electrical conductor is an electrical conductor carrying a low voltage current, the clipping means consist of four diodes mounted in series. 
         [0026]    According to a particular embodiment, when the electrical conductor is an electrical conductor carrying a very low voltage current, the clipping means consist of one diode. 
         [0027]    Advantageously, each diode has a maximum current intensity able to flow therein greater than the current intensity during the overvoltage. 
         [0028]    Advantageously, for each conductor, the number of diodes is the integral which is marginally greater than the ratio between the maximum voltage flowing in the electrical conductor and the limit voltage value at which the diode passes from a blocking state to a conducting state. 
         [0029]    A set comprising:
       a generator set comprising a power supply cable comprising several electrical conductors and at the end of which is set an end connector having an electrical contact for each electrical conductor,   an aircraft powered with electricity by means of said generator set and having a connection terminal having, for each electrical conductor, an electrical contact downstream of which is connected a conductor embedded in the aircraft and to which is connected at least one electrical component of the aircraft, and   a socket system according to previous embodiment.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    The characteristic features of the invention mentioned above, as well as other features, will appear more clearly from a reading of the following description of an example of embodiment, the said description being provided with reference to the attached drawings in which: 
           [0034]      FIG. 1  shows an aircraft on the ground connected to a generator set; 
           [0035]      FIG. 2  shows an extension socket according to the state of the art; 
           [0036]      FIG. 3  shows a partially cut-away view of a safety device according to an embodiment of the invention; and 
           [0037]      FIG. 4  shows an electrical diagram of the safety device according to an embodiment of the invention. 
           [0038]      FIG. 3  shows a safety device  100  which is designed to be implemented in conjunction with an extension socket  60  such as that shown in  FIG. 2  and in conjunction with an installation such as that shown in  FIG. 1 , together with a generator set  20  and an aircraft  10  comprising a connection terminal  50  for the protection against lightening of the aircraft  10 . The installation according to an embodiment of the invention presents a set comprising the generator set  20 , the aircraft  10  and a socket system such as described hereafter. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    The aircraft  10  is powered with electricity by the generator set  20  thanks to a power supply cable  30  comprising several electrical conductors and at the end of which is set an end connector  40  having an electrical contact for each electrical conductor. The aircraft  10  has a connection terminal  50  having, for each electrical conductor, an electrical contact downstream of which is connected a conductor  14  embedded in the aircraft  10  and to which is connected at least one electrical component  12  of the aircraft  10  to be protected. 
         [0040]    The extension socket  60  also comprises a first connector  62  which for each electrical conductor from the generator set  20  has an electrical contact which can be electrically connected to the said electrical conductor by means of an end connector  40 . 
         [0041]    The extension socket  60  also comprises a second connector  64  which has, for each electrical contact of the first connector  62 , an electrical contact  65  which is electrically connected to the said electrical contact of the first connector  62  and therefore to the associated electrical conductor. Each electrical contact  65  is designed to be connected to an electrical contact of the connection terminal  50 , an embedded conductor  14  being connected downstream of said electrical contact to electrical components  12  to be protected. 
         [0042]    The extension socket  60  also comprises a third connector  66  which has, for each electrical contact of the first connector  62 , a female electrical contact  68  which is electrically connected to the said electrical contact of the first connector  62  and therefore to the associated electrical conductor. 
         [0043]    In the context of the invention, the third connector  66  seats the safety device  100 . 
         [0044]    Of course, it is possible to provide an extension socket of another type where the electrical conductors A, B, C, E, F and N have a different layout and their number is different. 
         [0045]    The safety device  100  comprises:
       a housing  102  made of electrically insulating material;   for each female electrical contact  68 , a male electrical contact  106  made of electrically conductive material, projecting from the housing  102  and designed to be inserted in the said female electrical contact  68 ;   clipping means  108  designed to clip an electrical signal;   a printed circuit  104  seated inside the housing  102  and having conductive tracks connecting the male electrical contacts  106  and the clipping means  108 .       
 
         [0050]    Thus, by connecting the safety device  100  onto the third connector  66 , an electrical overvoltage on one of the electrical conductors is clipped by the clipping means  108  and the components of the aircraft  10  are protected. 
         [0051]    During normal mode, the clipping means  108  are transparent, while, beyond a certain voltage the clipping means  108  will clip the signal. 
         [0052]      FIG. 4  shows a diagram of an electric circuit  200  of the printed circuit  104  of the safety device  100  in a preferred embodiment. 
         [0053]    In this embodiment the first electrical conductors A, B and C are electrical conductors carrying a low voltage current which is preferably of the order of 115-200V at 400 Hz, the two electrical conductors E and F are electrical conductors carrying a very low voltage current which is preferably of the order of 28V and 0.5V and the third electrical conductor N is the neutral connected to earth. 
         [0054]    The first electrical conductors A, B and C are the phase conductors. 
         [0055]    The two electrical conductors E and F are called “discrete command conductors”. 
         [0056]    Clipping means  108   a , 108   b  are arranged between each male electrical contact  106  corresponding to a first electrical conductor A, B and C or to a second electrical conductor E and F, i.e. an electrical conductor A, B, C, E, F other than neutral N, and the male electrical contact  106  corresponding to neutral N. The clipping operation thus consists, in the case of an electrical overvoltage in an electrical conductor A, B, C, E, F, in setting this electrical conductor to the neutral which is itself connected to the earth of the aircraft  10 . 
         [0057]    Preferably, each clipping means  108   a ,  108   b  is an assembly consisting of a diode  204  or several diodes  202  mounted in series between the male electrical contact  106  corresponding to each electrical conductor A, B, C, E, F other than neutral N and the male electrical contact  106  corresponding to neutral N. 
         [0058]    In this embodiment of the invention, when the voltage in the electrical conductor A, B, C, E, F exceeds the limit voltage (also called “inversion voltage” or “clipping voltage” or also “clamping voltage”) of the diode or diodes  202 ,  204 , the latter are switched from a blocking state to a conducting state and start to conduct and transfer the electrical overvoltage towards the neutral N which is itself connected to the earth of the aircraft  10 . 
         [0059]    For each electrical conductor A, B, C, E, F, other than neutral N, departing from the generator set  20 , the characteristics and the number N of diodes  202 ,  204  are chosen depending on the conditions of use of the safety device  100 . 
         [0060]    The characteristics of a diode  202 ,  204  are as follows:
       the transition time between the blocking state and the conducting state,   the maximum current intensity able to flow in the diode  202 ,  204 , and   the limit voltage at which the diode starts to conduct.       
 
         [0064]    The conditions of use are as follows:
       the current intensity during the overvoltage,   for each electrical conductor, the maximum voltage flowing in the said electrical conductor (with preferably a margin of 10 to 15% corresponding to the conventional fluctuations of the voltage flowing in the generator set  20 ), and   the time interval for which each electrical component  12  to be protected may accept an overvoltage without suffering damage.       
 
         [0068]    For an electrical conductor and the associated embedded conductor  14 , each diode  202 ,  204  is firstly chosen so that its transition time is less than the time for which the electrical component  12  to be protected and electrically connected to the said embedded conductor  14  may be exposed to an overvoltage without damage; among these diodes  202 ,  204 , only those diodes  202 ,  204  which have a maximum current intensity able to flow therein greater than the current intensity during the overvoltage are retained. 
         [0069]    For each model of diodes  202 ,  204  which satisfies these two criteria and for each electrical conductor, the number N of diodes is thus the integral which is marginally greater than the ratio between the maximum voltage flowing in the electrical conductor and the limit voltage of the diode  202 ,  204 . 
         [0070]    With a view to optimization, the diode  202 ,  204  for which N is the smallest is chosen. 
         [0071]    It is also possible to take into account additional criteria. For example, the diodes  202 ,  204  which have a lower residual voltage will be preferred, preference being given to the diodes  202 ,  204  able to dissipate a greater power. 
         [0072]    In the case of the first electrical conductors A, B and C, the clipping means  108   a  consist of four diodes  202  which are identical and mounted in series. 
         [0073]    In the case of the two electrical conductors E and F, the clipping means  108   b  consist of a diode  204 . 
         [0074]    The diodes  202 ,  204  are for example diodes which are identified by the reference code 30KPA54CA or 30KPA58CA of the manufacturers Littlefuse. 
         [0075]    The safety device  100  and the extension socket  60  form a socket system according to the invention which is connected to the plurality of electrical conductors. 
         [0076]    In order to prevent the humidity or the dust from entering into the female electrical contacts  68  and the male electrical contacts  106 , the housing  102  is sealingly mounted on the extension socket  60 . 
         [0077]    According to a particular embodiment of the invention, the length of the conductor between the male electrical contact  106  corresponding to neutral N and the earth is less than 0.85 m and its resistance is less than 50 μΩ. 
         [0078]    While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.