Patent Publication Number: US-6343259-B1

Title: Methods and apparatus for electrical connection inspection

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. Pat. application Ser. No. 08/550,620, filed Oct. 31, 1995, now U.S. Pat. No. 5,733,041, which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to inspecting an electrical connection, or splice, between a power lead and a magnet wire and, more particularly, to methods and apparatus which may be utilized in determining the acceptability of such a splice. 
     BACKGROUND OF THE INVENTION 
     Dynamoelectric machines, such as motors and generators, typically include a magnetic core having a plurality of windings formed from magnet wire. For example, in one particular configuration, an electric motor includes a stator core having a stator bore. Side portions of a plurality of stator windings formed by the magnet wire are inserted into stator core slots having open ends at the periphery of the stator bore, and each end of the magnet wire extends from the stator core and is electrically connected, or spliced, to at least one power lead. 
     Magnet wire of a stator typically has a tough enamel coating. Such coating may enhance motor performance, for example, by electrically insulating each winding turn from other winding turns and protecting the magnet wire against damage which may cause reduced operational efficiency due to increased resistance of the magnet wire and possibly even short circuiting of the wire. 
     Although the enamel coating may enhance motor operation, such coating generally presents difficulties when attempting to form a reliable electrical connection, or splice, between a magnet wire and a power lead. For example, even though the insulation at the ends of the power leads may be stripped away so that the power lead conducting wires are exposed, it is time consuming and difficult to remove a segment of the enamel coating from each end of the magnet wires. 
     To reduce the time required to make electrical connections between stator magnet wires and power leads, a connector formed of electrically conducting material may be utilized. One known connector is, for example, substantially U-shaped and has a plurality of sharp serrations formed in the connector material on the interior surface of the connector. The stripped end of at least one power lead and one end of an enamel coated magnet wire may be placed within the interior of the U-shaped connector. A crimper may then fold the legs of the connector over the ends of the magnet wire and power lead, and may also squeeze, or crimp, the connector so that the sharp serrations are forced through the magnet wire enamel coating and into electrical contact with the magnet wire. Such crimping of the connector also may ensure that the connector is in electrical contact with the conducting wire at the stripped end of the power lead. An insulating sheath, which may be formed of heat-shrinkable insulating material, may then be placed over the crimped connector and heated so that the sheath shrinks and grips the connector. 
     Although the above described connector and crimping process generally form an acceptable electrical connection, or splice, between the magnet wire and power lead, there is a possibility that the magnet wire may “float-up”, or move within the connector toward the open end of the connector legs, during the crimping process. As a result, the serrations may not make good electrical contact with the magnet wire. For example, the serrations may not extend fully through the enamel coating and into firm contact with the magnet wire. If good electrical contact is not made between the magnet wire and the connector, motor performance may be adversely affected, for example, due to increased resistance and power loss at the connector. 
     Further, since manufacturing limitations may prevent high magnitude current stator winding testing, a bad electrical connection between a magnet wire and a power lead may not necessarily be detected until the motor actually is put in the field. High current testing generally is not performed on stator windings since such testing itself could damage the magnet wire. Also, even though a stator may pass low current tests at the manufacturing site, the vibrations and normal external conditions which a motor is exposed to during shipping may further deteriorate a bad electrical connection. As a result, the motor may not pass even low current tests when performed at the delivery site. 
     Early detection of bad electrical connections, especially prior to delivery, may facilitate reducing costs by avoiding costs associated with having motors deemed unacceptable at the delivery site or in the field due to bad electrical connections. Such early detection may also facilitate enhancing customer confidence. 
     With respect to the detection of unacceptable electrical connections, since such detection may be performed at a manufacturing site, it would be preferable to provide a manner of detecting such unacceptable connections which does not require substantial training and can be easily performed. In addition, rather than a mere qualitative, e.g., bad or good, measurement, a quantitative measurement indicative of the nature of an electrical connection may be preferred. A quantitative measurement may be more suitable, for example, for statistical process control applications in a manufacturing setting. For example, depending on the quantitative temperature measurement, a harder crimp may be required to form an acceptable splice. Further, to avoid an unacceptable increase in manufacturing time, such detection preferably would be performed rapidly. Such rapid detection would be particularly crucial in high volume manufacturing operations. 
     Accordingly, it would be desirable to improve motor reliability by facilitating the identification, based on quantitative measurements, of unacceptable electrical connections between stator magnet wires and power leads. It would also be desirable and advantageous to identify such unacceptable electrical connections without significantly increasing the costs and time associated with manufacturing a stator. 
     An object of the present invention is to improve motor reliability by facilitating early identification, based on quantitative measurements, of potentially unacceptable electrical connections between stator magnet wires and power leads. 
     Another object of the present invention is to quickly, and at a low cost, identify such potentially unacceptable electrical connections. 
     Still another object of the present invention is to facilitate reducing costs by reducing the quantity of motors which may be returned due to unacceptable electrical connections between stator magnet wires and power leads. 
     Yet another object of the present invention is to facilitate enhancing customer confidence by better ensuring that reliable electrical connections are made between stator magnet wires and power leads in delivered motors. 
     SUMMARY OF THE INVENTION 
     These and other objects may be attained by apparatus and methods for inspecting electrical connections, or splices, between stator magnet wires and power leads which, in one embodiment of the apparatus, includes a processing unit, a power supply unit, and a temperature sensing unit. The processing unit, in one embodiment, includes a programmable logic controller (PLC) having a central processing unit (CPU) and a plurality of input and output slots. The power supply unit, in one embodiment, includes a power lead connector designed to interconnect the motor power leads and a power control relay. The relay is coupled to and controlled by the PLC. The temperature sensing unit, in one embodiment, includes infrared thermometers and probes for sensing the temperature at the electrical connections, or splices, between the stator magnet wires forming the motor windings and the power leads. The outputs of the thermometers are coupled to an input slot of the PLC. 
     In one form of operation, and to determine whether a particular electrical connection is unacceptable, i.e., to determine the presence of electrical connection faults, the temperature sensing probe is positioned sufficiently near the electrical connection to sense or measure temperature at the connection. The operator may then depress a manual start switch, and the PLC causes the power relay to close and the motor windings are energized. While the windings are energized, the temperature sensing unit generates electrical signals representative of the temperature at the electrical connection, and such signals are supplied to the PLC. The CPU compares the signals received from the temperature sensing unit with at least one predetermined value stored in a suitable memory element. The predetermined value represents an upper temperature limit for an acceptable connection. 
     If the sensing unit output signal is above the predetermined value, then the connection may be unacceptable and the PLC generates a fault signal to energize a fault indicator, e.g., a light emitting diode (LED), to alert the operator that an electrical connection fault, such as a bad splice, may have been identified. Except as noted below, if the sensor output signal is below the predetermined value, then the connection is determined to be acceptable and no fault signal is generated. If the sensor output signal is substantially unchange from just prior to energization of the motor windings to the time at which the windings are energized, and even if the signal is below the predetermined value, then the connection may be unacceptable, e.g., an open circuit, and the PLC generates a fault signal. 
     The apparatus and methods described above improve motor reliability by facilitating the identification, based on quantitative measurements, of unacceptable electrical connections between stator magnet wires and power leads. Such apparatus and methods also enable identification of such unacceptable electrical connections without significantly increasing the costs associated with manufacturing a stator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a motor stator including a connector forming an electrical connection, or splice, between stator magnet wires and a power lead. 
     FIGS. 2A,  2 B,  2 C and  2 D are plan, side, front (with parts cut-away) and cross-section views, respectively, of one embodiment of a connector which may be utilized to form an electrical connection between stator magnet wires and power leads. 
     FIG. 3 is a circuit schematic diagram of one embodiment of an electrical connection inspection circuit. 
     FIG. 4 is a block diagram illustrating, in more one embodiment of a programmable logic controller which may be used in the inspection circuit illustrated in FIG.  3 . 
     FIG. 5 is a graph illustrating temperature difference with respect to input current as measured at a motor protector and connectors using an infrared detector. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a stator  10  including a magnetic core  12  and windings  14 ,  16 ,  18  and  20 . Windings  14 ,  16 ,  18  and  20 , for example, are formed by magnet wires  22 A and  22 B which are coupled, at electrical connector  24 , to a power lead  26 . Magnet wires  22 A and  22 B may be coated with a tough enamel coating as hereinbefore described. If a good electrical connection is not made by connector  24  between magnet wires  22 A and  22 B and power lead  26 , motor performance may be adversely affected due, for example, to increased resistance and power losses at connector  24 . 
     FIGS. 2A,  2 B,  2 C and  2 D illustrate one embodiment of electrical connector  24  which may be utilized to connect magnet wires  22 A and  22 B to power lead  26 . As shown in FIG. 2A, which is a top plan view, connector  24  includes serrations  28  formed in an interior surface  30  thereof. Connector  24  also includes an alignment portion  32  in which the magnet wires and power lead may be inserted so that the magnet wires and power lead are aligned with serrations  28 . 
     FIG. 2B is the side view of connector  24  and shows one leg  34 A which has serrations  28  (FIG. 2A) formed on an interior surface thereof and an alignment leg  36 A. Connector  24  also includes a substantially planar lower portion  38 , of course, a segment of portion  38  which extends between legs  34 A and  34 B has serrations formed thereon. Prior to crimping, the magnet wires and power lead preferably lie on, or are positioned adjacent to, portion  38 . 
     FIG. 2C is a view of connector  24  through line C—C in FIG.  2 B. As shown in FIG. 2C, connector. 24  is substantially U-shaped. Legs  34 A and  34 B may be folded over and crimped, as hereinafter described. 
     FIG. 2D is a cross-sectional view with parts cut-away of connector  24  through line D—D shown in FIG.  2 C. As clearly shown in FIG. 2D, serrations  28  extend from interior surface  30  of connector  24 . 
     Of course, many other types of connectors may be utilized to make an electrical connection, or splice, between stator magnet wires and power leads. Connector  24  is illustrated herein by way of example only. The inspection apparatus and methods described herein may be practiced with many other different types of connectors, and are not limited to use with connector  24 . 
     FIG. 3 is a schematic diagram illustrating one embodiment of an electrical connection, or crimp, inspection apparatus  50  which facilitates the early identification or detection of unacceptable electrical connections between stator magnet wires and power leads. Inspection apparatus  50 , in the illustrated embodiment, includes a master power switch  52  coupled to power lines L 1  and L 2  and a power lead connector  54  coupled to motor power leads MP 1  and MP 2 . Motor power leads MP 1  and MP 2  are connected to stator magnet wire leads MW 1  and MW 2  of a motor winding MW, such as either of windings  14 ,  16 ,  18  or  20  (FIG. 1) at connectors C 1  and C 2 . Electrical connectors C 1  and C 2  form electrical connections, or splices, between magnet wire leads MW 1  and MW 2  of motor winding MW and motor power leads MP 1  and MP 2 . Connector  24  illustrated in FIGS. 2A-D, or other known connectors, may be utilized to make such electrical connections. 
     Although two connectors C 1  and C 2  are illustrated in FIG. 3, it is contemplated that fewer or more connectors could be utilized depending upon the particular stator configuration. In any event, the number of connections, or splices, inspected during any particular testing cycle may vary, depending for example upon the number of such splices for a particular stator and the number of such splices desired to be inspected. For example, a stator may have only one connector, or more than two connectors, and apparatus  50  may be configured to inspect all such connectors for a stator during one testing cycle. 
     It also is contemplated that a fixture may be constructed so that a plurality, e.g., thirty to forty, of stators could be loaded onto the fixture and oriented so that inspections may be made for all such stators using inspection apparatus  50 . One stator represented as motor winding MW is shown in FIG. 3 for illustrative purposes only. Also, the fixture may be positioned within a safety cage so that the operator and others are prevented from accidentally contacting an energized stator during a testing cycle. Such a safety cage may include a guard gate having a solenoid-controlled lock which, as hereinafter explained, may be controllable by apparatus  50 . 
     Continuing with the description of FIG. 3, inspection apparatus  50  includes a first transformer T 1  for lowering 480 volts AC applied on its primary windings  56  to  115  volts AC output on its secondary winding  58 . Secondary winding  58  of transformer T 1  is coupled to a processing unit, shown as a programmable logic controller (PLC)  60 , secondary winding  58  also is coupled to a current meter  62  and a volt meter  64 . Secondary winding  58  of transformer T 1  also is coupled to duplex receptacles R 1  and R 2 . Receptacle R 2  is shown in block form and would be configured substantially similar to receptacle R 1 . Receptacle R 1  may be used, for example, for energizing a portable computer for reading and loading a memory of PLC  60 . Transformer T 1  may be a 500 VA control power transformer. Current meter  62  may be a 5 Amp ammeter, and volt meter  62  may be a 600 VAC volt meter. Further details regarding PLC  60  are provided hereinafter. 
     The temperature sensing unit also is coupled, via receptacle R 2 , to secondary winding  58  of transformer T 1  and includes infrared thermometers IT 1  and IT 2  electrically coupled to adapters  66  and  68 , respectively. Adapters  66  and  68 , which may be 110V AC adapters, are utilized to ensure that appropriate voltage level signals are supplied to thermometers IT 1  and IT 2 . The temperature sensing unit also includes infrared sensing probes  70  and  72 . Probes  70  and  72  transmit electromagnetic signals, such as infrared signals, to thermometers IT 1  and IT 2  so that thermometers IT 1  and IT 2  may generate, based on the probe transmitted infrared signals, temperature-indicative signals. Such temperature-indicative signals are supplied from thermometers IT 1  and IT 2  to PLC  60 . Thermometers IT 1  and IT 2  may be Omega Model 0S22 infrared thermometers including probes  70  and  72 , commercially available from Omega Engineering, Inc., P.O. Box 4047, Stamford, Conn. 06907-0047. 
     Each sensing probe  70  and  72  may be supported and held in place on the stator mounting fixture by a flexible, lamp-style gooseneck. The focus distance from each probe  70  and  72  to the respective electrical connector C 1  and C 2  may, for example, be about approximately 1.2 inches, which requires that the gooseneck be long enough to swing probes  70  and  72  clear of the fixture for loading of the stators. Depending upon the particular probe utilized, the distance from the probe to the splice may vary. Typically, the probe manufacturer specifies the preferred distance, i.e., focus distance, at which the probe lens should be positioned to obtain an accurate measurement. 
     If a safety cage is utilized as hereinbefore described, PLC  60 , current meter  62  and volt meter  64  may be mounted within the safety cage and viewable from outside of the cage, even when the safety cage gate is closed. Of course, it is contemplated that the PLC  60  and meters  62  and  64  could be mounted outside the cage. 
     The power supply unit includes a second transformer T 2 , coupled to master power switch  52 , having windings  74  and  76 . Transformer T 2  is a variable type transformer such as a 30 Amp 480/0-560 V Pac, and the output of variable transformer T 2  is coupled to a transformer T 3 , which may be a 10 KVA power transformer. Transformer T 3  includes four windings  78 ,  80 ,  82  and  84 , and windings  82  and  84  are tapped so that a voltage level ranging from about 0 to 183 volts may be applied to a power control relay  86 , which may be a commercially available solid state relay, such as relay Model Number D4875 available from Crydom, 6015 Obispo Ave., Long Beach, Calif. 90805. A current meter  88  is coupled, via current transformer  90 , to an output of relay  86  and a volt meter  92  is connected across windings  82  and  84 . Current meter  88  may be a 5 amp ammeter and current transformer  90  may have a 100:5 ratio. Volt meter  92  may be a 600 VAC volt meter. Current and volt meters  88  and  92  may be utilized to ensure an operator that an appropriate signal is supplied to energize motor winding MW via power lead connector  54 . The form of connector  54  may, of course, vary depending upon the particular stator desired to be inspected. Connector  54  may, for example, include ejector style power terminals for coupling to motor power leads MP 1  and MP 2 . 
     A plurality of circuit breakers B 1 , B 2 , B 3  and B 4 , which may be 35 Amp 600 volt circuit breakers, are provided to protect the various components of apparatus  50  from damage. Of course, many other types of protectors may be utilized. 
     FIG. 4 is a block diagram illustrating, in more detail, one embodiment of programmable logic controller  60 . Controller  60  may, for example, be PLC Model No. D3-05BOC, commercially available from-PLC Direct By Koyo, 315 Allen Street, Cumming, Ga. 30130. Controller  60  includes a central processing unit (CPU)  100  and four slots labelled SLOT  0 - 3 . CPU  100  may, for example, be a 3.7K word CPU. By way of example, SLOT  0  includes an 8 channel (millivolt) analog input. Output signals from infrared thermometers IT 1  and IT 2  which are representative of the temperatures sensed at connectors C 1  and C 2 , for example, are supplied as analog inputs at SLOT  0 . Such thermometer output signals are digitized by a suitable analog-to-digital convertor (not shown) and supplied to CPU  100  for further processing as hereinafter described. 
     SLOT  1  is a 24 volt DC sink output which is coupled to power control relay  86 . More particularly, relay  86  is normally non-conducting or open. When an operator depresses a manual touch start switch, and if other preconditions are satisfied, a logic signal is supplied from SLOT  1 , for a predetermined period of time under the control of CPU  100 , to relay  86 . The logic signal from SLOT  1 , coupled with the 24V DC signal supplied by PLC  60  to relay  86 , causes relay  86  to transition to its conductive state. When CPU  100  causes the logic signal from SLOT  1  to be low and cuts-off the 24V DC signal, relay  86  once again becomes non-conductive. 
     SLOT  2  has eight input lines for receiving  110  volt AC signals. Slot  2  receives inputs from, for example, a manual start switch, the guard gate lock and a guard gate closed status indicator. The signal levels on these input lines indicate the status of various switches and components and may be utilized by CPU  100  to control, for example, the energization of the stator windings. For example, CPU  100  may control the SLOT  1  logic signal so that such signal is “high” only if the inputs at SLOT  2  indicate that the guard gate is closed and locked after the manual start switch has been depressed. 
     SLOT  3  is made up of a 115 volt AC eight line output. Outputs from SLOT  3  are supplied, under the control of CPU  100 , to a guard lock control solenoid and status indicators. The guard lock control solenoid may be utilized to prevent an operator from opening the guard gate of the safety cage while an electrical connection test in accordance with the present invention is in progress. The status indicators may include separate indicators for indicating that a test is in progress and a guard lock fault, e.g., if the lock on the safety cage door is not locked. Also, a respective indicator may be associated with each thermometer IT 1  and IT 2  to indicate whether an unacceptable electrical connection has been detected. Such indicators may be color coded LEDs, for example. 
     PLC  60  also may include other elements such as electronic memory storage elements, e.g., ROM and RAM memory elements. Also, PLC  60  includes AC common (COM) and positive (HOT) connections to couple PLC  60  to an energy source. A stabilizing/filtering capacitor C is connected to a terminal of PLC  60  normally utilized for coupling PLC  60  to an extension rack. It is contemplated, of course, that many different types of programmable logic controllers may be utilized, and PLC  60  is just one of many PLCs that may be used. 
     In one form of operation of apparatus  50 , and to inspect electrical connections, or splices, a plurality of stators may be loaded on the fixture within the safety cage. Probes  70  and  72  may then be positioned at the proper focus distance from, for example, connectors C 1  and C 2 , respectively, for a particular stator to be inspected. The safety cage gate of the fixture is then closed and locked. Master power switch  52  also should be closed. 
     An operator may initiate the inspection by depressing the start switch coupled to SLOT  2  of PLC  60 . After such start switch has been depressed, and if the guard gate is closed and locked as indicated by signals received at SLOT  2  of PLC  60 , PLC  60  supplies a “high” logic signal from SLOT  1  to power relay  86 . The 24V DC output from PLC  60  also is supplied to relay  86  so that relay  86  transitions from a non-conductive to a conductive state. CPU  100  enables such logic signal and a 24V DC output signal for a predetermined period of time, e.g., 8 seconds. It is contemplated that such 24V DC signal may also be applied to a control solenoid for a guard gate lock to maintain the guard gate closed and locked while the logic signal output from SLOT  1  is “high”. The signal supplied to such control solenoid from SLOT  3  serves as a logic signal to enable such solenoid for the test period. Also, under the control of CPU  100 , a signal output from SLOT  3  energizes a test in progress indicator, and such indicator remains “on” while the logic signal output from SLOT  1  is “high”. 
     If the guard gate of the safety cage is not closed and locked when the start switch is depressed, then CPU  100  causes a signal to be supplied from SLOT  3  to the guard lock fault indicator while no logic signals are supplied from SLOT  1  to power relay  86  and from SLOT  3  to the guard gate lock control solenoid. As a result, relay  86  will remain open and motor winding MW will not be energized under such conditions. 
     If the predetermined conditions are satisfied and motor winding MW is energized, while power is applied to motor power leads MP 1  and MP 2 , infrared probes  70  and  72  transmit infrared signals to thermometers IT 1  and IT 2 . Thermometers IT 1  and IT 2  receive the transmitted infrared signals so as to generate analog electrical signals representative of the temperatures at connectors C 1  and C 2 , respectively, and the analog signals are in turn supplied to SLOT  0  of PLC  60 . 
     To determine whether connections formed by connectors C 1  and C 2  are acceptable, and in one exemplary embodiment of operation, CPU  100  compares such infrared thermometer input signals with predetermined values, stored in memory of PLC  60 , to determine whether such signals are within a predetermined, acceptable range. If such signals are within an acceptable range, then no fault indicators are turned on by CPU  100  via SLOT  3 . If a signal from a particular thermometer IT 1  and IT 2  is not within an acceptable range, then CPU  100 , via SLOT  3 , turns on a fault indicator associated with such thermometer IT 1  and IT 2 . 
     In another embodiment, temperature differentials may be utilized to determine whether connections C 1  and C 2  are acceptable. Particularly, a temperature differential may be determined by first determining an ambient temperature at the electrical connections prior to energizing the associated motor winding. Infrared probes  70  and  72  may, for example, be used to obtain such ambient temperature, i.e., pre-energization measurement data. Then the motor winding is energized using, for example, a voltage magnitude of about seventy-five percent of the magnitude of the rated voltage for the subject stator. Of course, other voltage values and time periods may be utilized depending on the specific stator characteristics. 
     As the winding is energized, thermometers IT 1  and IT 2  supply temperature-representative signals to SLOT  0  of PLC  60 . CPU  100  processes signals received from thermometers IT 1  and IT 2  by subtracting the value of the initial ambient temperature signal from the value of the sensed temperature signal to obtain a differential temperature value for each respective thermometer IT 1  and IT 2 . CPU  100  then compares the differential temperature value with a predetermined value stored in PLC memory, and if the differential temperature value is less than the stored, predetermined value, no fault indicator is energized by a SLOT  3  output signal. However, if the differential temperature value is greater than the stored, predetermined value, then CPU  100  causes a signal to be output from SLOT  3  to energize a fault indicator associated with the thermometer supplying the respective sensed temperature signal to SLOT  0 . Also, if the differential temperature value is approximately about equal to zero, then CPU  100  causes a signal to be output from SLOT  3  to energize a fault indicator associated with the thermometer supplying the respective sensed temperature signal to SLOT  0 . Such a condition, i.e., when the differential temperature equals about zero, indicates an open circuit condition. 
     FIG. 5 is a chart illustrating input current (x-axis) versus temperature differential (y-axis) as measured with infrared thermometers for a particular motor. Line OP illustrates the measurements at an overload protector, line AC illustrates the measurements for an acceptable electrical connection, and line UC illustrates the measurements for an unacceptable electrical connection. As clearly shown in the diagram in FIG. 5, an unacceptable electrical connection exhibits a significantly higher temperature differential, even at low currents, as compared to an acceptable electrical connection. The overload protector temperature differential is provided only as a reference curve to facilitate an understanding of motor heating. 
     The predetermined stored values in the PLC memory may be obtained by measuring the temperature at an electrical connector which is known to be making a good electrical connection between a power lead and magnet wire. Of course, more than one such electrical connection could be inspected to determine an upper temperature differential limit. Once such an upper limit is so identified, the value of such limit is stored in the PLC memory and may be utilized by CPU  100  as described above. 
     Further, rather than using just one temperature value in making a binary, e.g., acceptable or unacceptable, type decision, different values can be utilized as indicators as to the acceptability of a particular connection. For example, a first value may be established to correlate to an acceptable connection. A second value may be established to correlate to a connection which may require further testing to determine whether such connection is acceptable. A third value may be established to correlate to an unacceptable connection. 
     Of course, it is contemplated that rather than utilizing temperature comparison or temperature differential values, temperature ratios or other values indicative of the temperature characteristics exhibited at the electrical connections when the windings are energized could similarly be determined by CPU  100  and utilized to identify unacceptable electrical connections. 
     With respect to the detection of unacceptable electrical connections between stator magnet wires and power leads with the apparatus and methods described above, use of such apparatus and methods do not require substantial training and can be quickly and easily performed. In addition, such apparatus and methods provide a quantitative measurement indicative of the nature of an electrical connection. Specifically, the analog signals supplied to PLC  60  by thermometers IT 1  and IT 2  are digitized and such digitized value may be stored in the PLC memory and readily accessible for use in, for example, statistical process controls for a crimping operation. For example, if a crimp is formed using a known force applied by the crimper to the connector, and it the resulting connection is unacceptable, in future crimping operations, a greater force may be determined to be necessary to form an acceptable connection. Further, the apparatus and methods enable identification of unacceptable connections after the stator has been fully assembled to sort such stators into separate groups based on the acceptability of such connections. 
     From the preceding description, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.