Abstract:
A method and an apparatus for determining the electric resistances of coil connections (RSi) of connections ( 1 - 12 ) of coils (Bi) of a winding ( 102 ) of a dynamo electric machine, which includes a plurality of coils (Bi) connected in series. A first current (I 1 ) is generated through a first coil connection ( 1 ) of a first coil (B 1 ) of the winding ( 102 ). Furthermore, a second current (I 2 ) is generated through a first coil connection ( 3, 7 ) of a second coil (B 2,  B 6 ) of the winding in such a way as to eliminate the current flowing through a portion (B 8 -B 11 ) of the winding, which is proximate to the first coil connection ( 1 ) of the first coil (B 1 ) and the first coil connection ( 3,7 ) of the second coil (B 2,  B 6 ). A third current ( 13 ) is also generated in a second coil connection ( 2 ) of the first coil (B 1 ). The generating of the first current (I 1 ), the generating of the second current (I 2 ), and the generating of the third current (I 3 ) are made with respect to a common potential ( 13 ). Measurements are made of a first voltage (V 1 ) across a third coil (B 12 ), which is adjacent to the first coil (B 1 ), and of the current (I 1 ) flowing through the first coil connection ( 1 ) of the first coil (B 1 ). From these measurements a determination is made of the resistance (RS 1 ) of the first coil connection ( 1 ) of the first coil (B 1 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention concerns processes and apparatus for determining coil connections&#39; resistance and coils&#39; electric resistance by means of testing machines used in production lines for manufacturing dynamoelectric core components and their related windings, for example in the manufacturing of armatures of electric motors. 
         [0002]    A coil connection is typically made for each coil to a commutator bar, or other terminal means for passage of electric current between each coil and an external supply. The coil connection is normally accomplished by positioning and fusing the lead conductor of the coil to or terminal, which has the form of a hook (“tang”) or other suitable configuration. 
         [0003]    Fusing machines for permanently anchoring a lead conductor to a commutator bar have been described in EP 0419, 849 A1. Machines for forming coils of windings of cores of dynamoelectric machines have been described in EP 484,766 A2. 
         [0004]    The quality of the manufactured connection is verified by testing devices, which measure the electrical resistance of the connections to the commutator bar, or to any other type of terminal means. This electrical resistance is indicative of the quality of the connection made, i.e. whether the lead has been anchored with the required electrical and mechanical properties. 
         [0005]    In addition to measuring the electrical resistance of the coil connections, the electric resistance of the coils is also verified. The electric resistance of a coil is indicative of the number of turns that have been wound, and whether the conductor has been excessively elongated or insufficiently tightened by the tension applied during winding. 
         [0006]    A process for determining the electric resistance of coil connections of a winding of a dynamoelectric machine having the characteristics of the preamble of method claim  1 , and an apparatus according to the preamble of claim  8  have been described in U.S. Pat. No. 4,651,086 and EP 695,946A2. 
         [0007]    The testing device of the foregoing prior art circulates electric current each time only through certain coils of the winding that have connections that need to be determined. In addition, a feedback regulating loop circuit is used to eliminate the current circulating in a remaining series of coils, whilst maintaining the opposite leads of this remaining series of coils substantially at the same voltage. In this way, the measurement and knowledge of the voltage and current of the coils where the current is circulating makes it possible to determine their electric resistance and the electric resistance of their connections. 
         [0008]    The drawback of this prior art is that the current circulating through the coils that are being verified is influenced and in part derives from the above mentioned feedback regulating loop circuit. During the measurements, the regulation requires a certain stabilization time before taking reliable test values. In other words, a certain waiting time is required before making the measurements that determine the coil connections&#39; electric resistance and the coils&#39; electric resistance. The waiting time is typically due to the filtering effect of the feedback regulation system. The waiting time is a penalizing time, which decreases the number of cores that can be tested in a certain time by a testing machine. 
         [0009]    In addition to the above, a same testing machine is often used both for measuring the coil connections&#39; resistance, and the coils&#39; electric resistance of cores, where the coils have significantly different sizes. These coils of different core categories can have very different inductive and electric resistance ranges. Consequently, and particularly in the situation of coils having large electric resistance values, the small current that is applied for carrying out the measurement can easily be partially dispersed. This results in less precision in the determination of the coil connection electric resistance and the coil electric resistance. 
       Object of the Invention 
       [0010]    It is thus an object of the present invention to provide a method and apparatus of the type mentioned above in which the determination of the coils&#39; electric resistance can be more rapid. 
         [0011]    It is also an object of the present invention to make it possible to be more rapid in the determination of the coils&#39; electric resistance. 
         [0012]    It is another object of the present invention to make the determination of the connections&#39; electric resistance more accurate. 
         [0013]    It is also an object of the present invention to make the determination of the coils&#39; electric resistance more accurate. 
         [0014]    It is another object of the present invention to provide a method and an apparatus, which are capable of determining the coil connections&#39; electric resistance, or the coils&#39; electric resistance using test voltages, or test currents that are particularly suited for the size of the coil being tested. 
       SUMMARY OF THE INVENTION 
       [0015]    According to the invention the foregoing scopes are achieved using a process as indicated in claim  1  and an apparatus as indicated in claim  8 . 
         [0016]    The process and apparatus of the present invention uses a regulation circuit capable of eliminating the current in the coils that do need to be determined, however without influencing the current that needs to circulate in other coils where the measurements need to be made. In other words, the electric currents used for measuring the coil connections&#39; electric resistance and the coils&#39; electric resistance can be independent of the current used by the regulation circuit for eliminating the current passing in the remaining series of coils of the winding. 
         [0017]    In this way, it is also possible to use current measurements, which are specifically suited for the size of the coils whose resistance needs to be measured. This results in the testing machine being particularly accurate for testing a plurality of different sizes of coils. 
     
    
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
         [0018]    Further features and advantages of the present invention will become apparent from the following description, given purely by way of non-limiting example with reference to the accompanying drawings, in which: 
           [0019]      FIG. 1  is an example of a dynamo electric component comprising an armature provided with a winding having fused coil connections, 
           [0020]      FIG. 2  is a circuit diagram showing the measurement of the various coil connections&#39; electric resistances and the various coils&#39; electric resistances in accordance with a first embodiment of the invention, 
           [0021]      FIG. 3  is a circuit diagram showing the measurement of the various coil connections&#39; electric resistances and the various coils&#39; electric resistances in accordance with a second embodiment of the invention, 
           [0022]      FIG. 4  is a circuit diagram showing the measurement of the various coil connections&#39; electric resistances and coils&#39; electric resistances in accordance with a third embodiment of the invention, 
           [0023]      FIG. 5  is a schematic circuit diagram showing the use of analog and digital components for the measurement of the various coils&#39; connection resistances and coils&#39; resistances in accordance with the embodiment of  FIG. 3 . 
       
    
    
       [0024]    With reference to  FIGS. 1 and 2 , the resistance of the various coil connections are labeled RS 1 , RS 2  etc. . . . These are typically the electrical resistances encountered by the current passing from each coil  102  of the core winding through the joint that is created between the wire of the coil and an external connection member, like a commutator bar  100 , or other suitable terminal. In the case of  FIG. 1 , the joints are fused connections on hooks (“tang”) like  101 . The electric resistance of the various coils  102  are indicated as B 1 , B 2  . . . and their electrical resistances are indicated respectively as RB 1 , RB 2  etc. . . . Each electric resistance RBi of a generic coil Bi is influenced by the number of turns of wire that have been wound to form the coil and the resulting diameter of the wire that forms the coil. For example, a coil that has been wound with a number of turns that are different from the prescribed value, or has been wound by using an incorrect tension, will have an unacceptable electric resistance RBi. 
         [0025]    For example, a tang joint where the wire insulation has not been properly removed during fusing, or where the surface of the tang connection on the commutator bar is insufficient, will have an unacceptable electric resistance RSi. 
         [0026]    Connection members  1 - 12  of  FIG. 2-5  can be considered the circuit representation of commutator bars  100  of  FIG. 1 . 
         [0027]    During a measurement step to determine a coil connection electric resistance like RS 1  and a coil electric resistance like RB 1  (see  FIG. 2 ) a fixed current I 1  is induced, for example by a voltage generator G 1 , which applies a voltage to connection member  1  with respect to a potential point  13 . Potential point  13  can be for example a mass point, as shown in  FIG. 2 . 
         [0028]    In addition, a circuit for inducing a variable current, which can be for example a variable voltage generator G 2 , applies a voltage to the connection member  3  with respect to the potential point  13 . The voltage generator G 2  is controlled by a regulation circuit R, which receives the voltage levels existing between the connection members  12  and  4 . The regulation circuit R controls with a feedback signal generator G 2  to assure that the tension between the connection members  12  and  4  is negligible, and therefore that current I 0  which circulates in electric resistances of the coils including RB 11  and RB 4  is negligible. More particularly, regulator R accomplishes that the tension in connection members  12  and  4  is precisely the same, so that there is no current flowing in the coil resistances going from RB 11  o RB 4 . 
         [0029]    Furthermore, with reference to  FIG. 2 , a fixed current I 3  is induced, for example by a voltage generator G 3 , which applies a voltage to connection member  2  with respect to the same potential point  13 . 
         [0030]    With this arrangement, generators G 1  and G 2  are required and dedicated to eliminating current I 0 , whilst generator G 3  is required and dedicated to supplying the measurement currents. 
         [0031]    As a result of this arrangement, current I 1  from generator G 1  is flowing in coil connection resistance RS 1  of the coil connection  1  and in coil resistance RB 1 , and current I 2  resulting from generator G 2  is flowing in coil connection resistance RS 3  of the coil connection  3  and in coil resistance RB 2 . 
         [0032]    Current I 1  can be measured by means of ammeter A 1 . Current I 2  can be measured by means of ammeter A 2 . The sum of currents I 1  and I 2  is equal to current I 3 . 
         [0033]    The voltage between connection members  1  and  12  can be measured with voltmeter V 1 . The voltage between connection members  3  and  4  can be measured with voltmeter V 2 . 
         [0034]    A negligible current is flowing in coil resistance RB 11  seeing that it belongs to the winding portion where the current is eliminated by regulation circuit R. Also negligible is the current flowing through resistance RS 12  of connection  12 , and through resistance RB 12  of coil B 12 . 
         [0035]    Therefore, connection resistance RS 1  of connection  1  can be determined from the relation V 1 /I 1 . 
         [0036]    Similarly, RS 3  can be determined from the relation V 2 /I 2 . 
         [0037]    The voltage between connection members  12  and  2  can be measured with voltmeter V 3   
         [0038]    RB 1  can be determined from the equation: 
         [0000]        RB 1 *I 1 +RS 2*( I 1 +I 2)= V 3, 
         [0039]    In fact, considering that RS 2  is many times smaller than resistance RB 1 , then the addend RS 2 *(I 1 +I 2 ) can be considered null in the above equation, and consequently RB 1  can be determined from 
         [0000]        RB 1 =V 3 /I 1. 
         [0040]    If this approximation is not desired, then prior to using the above equation for determining RB 1 , resistance RS 2  can be determined by carrying out steps like those that have been described above for determining RS 1 . This can be achieved with generators G 1 , G 3  and G 2  applied respectively to connection members  2 ,  3 , and  4 , and with ammeters A 1  and A 2  respectively applied along lines of connection members  2  and  4 . In this situation voltmeter V 1  is applied between connection members  1  and  2 , V 2  is applied between connection members  4  and  5 , and V 3  is applied between connection members  1  and  3 . This entire modified arrangement can be accomplished by indexing the core in a clockwise direction by an angular spacing equal to the angle separating two adjacent connection members like connection members  1  and  2 . 
         [0041]    For the measurements steps required to determine RS 1 , RB 1  and RS 2 , the voltages applied by generators G 1  and G 2  can be chosen in values with the primary scope of eliminating the current I 0  by using the regulation of G 2 , whilst the voltage applied by generator G 3  is chosen with the purpose of having a more adequate current for carrying out the determination of the coil resistances and the connection resistances. 
         [0042]    By using this approach, the generation of voltages for the current I 0  elimination is independent of the generation of the voltage applied for receiving the current used to measure the resistances. 
         [0043]    It is possible to accomplish successive index steps of the armature and corresponding measurement steps, like has been described in the foregoing, in order to determine all the coil connection resistances RS 1 -RS 12 , and all the coil resistances RB 1 -RB 12 . 
         [0044]      FIG. 3  is an arrangement in which two connection resistances RS 1  and RS 7  and two coil resistances RB 1  and RB 6  can be determined before needing to index the core. This results in being able to save time in the measurements. 
         [0045]    More particularly, in this embodiment generator G 1  can be connected to connection member  1 . Generator G 2  can be connected to connection member  7 , and generator G 3  can be connected to connection members  2  and  6 . Generator G 2  can be regulated by regulation circuit R to eliminate the passage of current I 0  in the coils connected between connection member  12  and connection member  8   
         [0046]    The following equations can apply: 
         [0000]        RS 1 =V 1 /I 1, 
         [0047]    where V 1  and I 1  can be measured respectively by voltmeter V 1  and ammeter A 1 , and therefore RS 1  can be determined. 
         [0000]        RB 1 *I 1 +RS 2 *I 3 =V 3, 
         [0048]    from which RB 1  can be determined, seeing that currents I 1  and I 3  can be measured respectively by ammeter A 1  and ammeter A 3 , and V 3  can be measured by voltmeter V 3 . RS 2  can be determined after one angular index and using measurement steps, like those performed for determining RS 1 . As an alternative RS 2  can be considered negligible with respect to RB 1 , therefore RS 2 *I 3  can be considered null in the equation, which thus results in 
         [0000]        RB 1 =V 3 /I 1. 
         [0049]    For the same angular position of the commutator: 
         [0000]        RS 7 =V 2/ I 2, 
         [0050]    where V 2  and I 2  can be measured respectively by voltmeter V 2  and ammeter A 2 , and therefore RS 7  can be determined. 
         [0000]        RB 6 *I 2+ RS 6* I 4= V 4, 
         [0051]    from which RB 6  can be determined, seeing that I 2  and I 4  can be measured respectively by ammeter A 2  and ammeter A 4 , and V 4  can be measured by voltmeter V 4 . Resistance RS 6  can be determined after one angular index, and a series of measurement like those performed for determining RS 7 . As an alternative, RS 6  can be considered negligible with respect to RB 6 , like has been indicated above for RS 2  compared to RB 1 , therefore: 
         [0000]        RB 6= V 4/ I 2. 
         [0052]      FIG. 4  illustrates another arrangement in which two connection resistances RS 1  and RS 7 , and two coil resistances RB 1  and RB 6  can be determined before needing to index the core. The arrangement of  FIG. 4  uses two generators G 3  and G 4  instead of one generator G 3 , like is shown in  FIG. 3 . The two generators G 3  and G 4  of  FIG. 4  will be smaller and need to produce approximately half the current, if compared with the single generator G 3  used in the solution of  FIG. 3 . 
         [0053]    In the solution of  FIG. 4 , generator G 1  can be connected to connection member  1 . Generator G 2  can be connected to connection member  7 , and generator G 3  can be connected to connection member  2 , whilst generator G 4  can be connected to connection member  6 . Generator G 2  can be regulated by regulation circuit R to eliminate the passage of current I 0  in the coils connected between connection member  12  and connection member  8   
         [0054]    The following equations can apply: 
         [0000]        RS 1= V 1/ I 1, 
         [0055]    where V 1  and I 1  can be measured respectively by means of voltmeter V 1  and ammeter A 1 , therefore RS 1  can be determined. 
         [0000]        RB 1* I 1+ RS 2* I 3= V 3, 
         [0056]    From which RB 1  can be determined, seeing that I 1  and I 3  can be measured respectively by ammeter A 1  and ammeter A 3 , and V 3  can be measured by voltmeter V 3 . RS 2  can be determined after one angular index and a series of measurement like those performed for determining RS 1 . As an alternative RS 2  can be considered negligible with respect to RB 1 , therefore RS 2 *I 3  can be considered null in the equation, thus: 
         [0000]        RB 1= V 3/ I 1. 
         [0057]    For the same angular position of the commutator there is also that: 
         [0000]        RS 7= V 2/ I 2, 
         [0058]    where V 2  and I 2  can be measured respectively by voltmeter V 2  and ammeter A 2 , and therefore RS 7  can be determined. 
         [0000]        RB 6* I 2+ RS 6* I 4= V 4, 
         [0059]    From which RB 6  can be determined seeing that I 2  and I 4  can be measured respectively by ammeter A 2  and ammeter A 4 , and V 4  can be measured by voltmeter V 4 . 
         [0060]    Resistance RS 6  can be determined after one angular index, and by carrying out a series of measurement like those performed for determining RS 7 . As an alternative RS 6  can be considered negligible with respect to RB 6 , like has been described in the foregoing in the comparison of RS 2  with respect to RB 1 , therefore: 
         [0000]        RB 6= V 4/ I 2. 
         [0061]      FIG. 5  shows the circuit diagram for a solution where digital components are used in the testing machine for carrying out measurements and determinations like those described with reference to  FIG. 4 . 
         [0062]    An analog digital converter  50  receives analog signal V 1  in channel  50   a  and converts the measurement into digital data, which is transferred to central processing unit (CPU)  52  via BUS  51 . 
         [0063]    Analog signal A 1  from a measurement resistance RM is received in channel  50   b  and is converted into digital data, which are transferred to CPU  52  via BUS  51 . 
         [0064]    Analog signal V 3  is received in channel  50   c  and is converted into digital data, which are transferred to CPU  52  via BUS  51 . 
         [0065]    Analog signal A 3  from a measurement resistance RM 3  is received in channel  50   d  and is converted into digital data, which are transferred to CPU  52  via BUS  51 . 
         [0066]    A second digital converter  53  receives analog signal V 2  in channel  53   a  and converts the measurement into digital data, which are transferred to CPU  52  via BUS  54 . 
         [0067]    Analog signal A 2  from a measurement resistance RM 1  is received in channel  53   b  and is converted into digital data, which are transferred to 
         [0068]    CPU  52  via BUS  51 . 
         [0069]    Analog signal V 4  is received in channel  50   c  and is converted into digital data, which are transferred to CPU  52  via BUS  53 . 
         [0070]    Voltage feedback of regulation circuit R is connected to channel  53   d  so that the difference in tension between connection members  12  and  8  is fed as digital data to CPU  52 . 
         [0071]    Analog signal A 4  from a measurement resistance RM 4  is received in channel  53   e  and is converted into digital data, which is transferred to CPU  52  via BUS  51 . 
         [0072]    CPU  52  elaborates the measurement and solves the equation as described in the foregoing to determine the various resistances. Furthermore, CPU  52  send drive signals to digital generators G 1 , G 2 , G 3 , G 4  along respective lines g 1 , g 2 , g 3 , g 4  to induce currents I 1 , I 2 , I 3 , I 4  and make negligible current I 0 , as has been described in the foregoing. 
         [0073]    Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and shown purely by way of example, without departing from the scope of the present invention.