INSULATION TEST SYSTEM WITH VOLTAGE AND CURRENT COMPENSATION CIRCUIT

Abstract

An insulation testing system comprises: a set of input terminals; a brush; a circuit connected to the set of input terminals, the brush, and a part under test, the circuit comprising at least one of a pair of resistors and a capacitor; and a control module configured to detect when a short circuit exists between a conductive element of the part and one or more conductive bristles due to the absence of insulating material on the part and, as a result, the one or more conductive bristles of the brush contact the conductive element of the part.

Description

INTRODUCTION

[0001] The present disclosure relates to continuity testing systems and, more particularly, to insulation testing systems for testing stator windings and other electrical components.

[0002] Electric and hybrid vehicles include traction motors for propulsion. Each traction motor includes a stator and a rotor with corresponding windings and conductive bars. The windings and / or conductive bars may be insulated (e.g., have an outer insulating coating). During manufacturing, including the molding and assembly of parts and components, the insulating coatings may not be properly formed or may become nicked, scratched, abraded, etc. This can result in sections of the insulating coatings being missing and / or removed, exposing electrically conductive elements. This stress can cause a short circuit, impair motor performance, and / or shorten motor life.

[0003] DE 10 2014 107 025 A1 describes an insulation testing system comprising a set of input terminals, a brush, a circuit having a resistor connected to the set of input terminals, the brush, and a part under test, and a control module. The control module is configured to detect when a short circuit occurs between a conductive element of the part and one or more conductive bristles due to the absence of insulating material on the part, and as a result, the one or more conductive bristles of the brush contact the conductive element of the part.

[0004] US 10 132 854 B2 describes an insulation testing system with features according to a similar technology. SUMMARY

[0005] An insulation testing system is disclosed and comprises: a set of input terminals; a brush; a circuit connected to the set of input terminals, the brush, and a part under test, the circuit comprising at least one of a pair of resistors and a capacitor; and a control module configured to detect when a short circuit exists between a conductive element of the part and one or more conductive bristles due to the absence of insulating material on the part and, as a result, the one or more conductive bristles of the brush contact the conductive element of the part.

[0006] Furthermore, the set of input terminals includes a positive terminal and a negative terminal. The capacitor and a first resistor of the resistor pair are connected in series between the positive and negative terminals.

[0007] In addition, the set of terminals includes a common terminal separated from the positive and negative terminals. A second resistor of the resistor pair is connected between the negative terminal and the common terminal.

[0008] In other features, the circuit is implemented as a voltage and current balancing circuit, and the circuit includes the resistor pair and the capacitor connected in series between the positive terminal and the common terminal.

[0009] In other features, the capacitor is connected across a power source and between the positive terminal and the negative terminal.

[0010] In other features, the first resistor comprises i) a first end connected to a first end of the capacitor, and ii) a second end connected to a first of the set of input terminals and to the brush. The second resistor comprises i) a first end connected to a second of the set of input terminals, to a second end of the capacitor, and to the part, and ii) a second end connected to a third of the set of input terminals.

[0011] In other features, the first end of the capacitor is connected to a positive terminal of the power source. The second end of the capacitor is connected to a negative terminal of the power source.

[0012] In other features, a lead is connected between i) the second of the set of input terminals, the first end of the second resistor and the second end of the capacitor and ii) one or more 3-phase contacts of the part.

[0013] In other features, the insulation testing system further includes an analog-to-digital converter connected to the circuit and configured to convert an analog signal output by the circuit into a digital signal. The control module is configured to detect, based on the digital signal, when a short circuit exists between the conductive element of the part and the one or more conductive bristles.

[0014] In other features, the control module is configured to generate at least one of a message or an alarm when a short circuit is detected between the conductive element of the part and the one or more conductive bristles.

[0015] In other features, an unclaimed insulation testing method is disclosed, comprising: connecting a lead to a part to be tested; moving a brush over a portion of the part or moving the part relative to the brush; detecting a voltage drop across a pair of input terminals via a circuit, the circuit being connected to the pair of input terminals, the brush, and the part, and the circuit comprising at least one of a pair of resistors and a capacitor; and determining whether the voltage drop indicates that a short circuit exists between a conductive element of the part and one or more conductive bristles due to the absence of insulating material on the part and, as a result, the one or more conductive bristles of the brush contact the conductive element of the part.

[0016] In other features, the set of input terminals includes a positive terminal and a negative terminal. The capacitor and a first resistor of the resistor pair are connected in series between the positive terminal and the negative terminal.

[0017] In other features, the set of terminals includes a common terminal separated from the positive terminal and the negative terminal. A second resistor of the resistor pair is connected between the negative terminal and the common terminal.

[0018] In other features, the set of terminals includes a positive terminal, a negative terminal, and a common terminal. The circuit is implemented as a voltage and current balancing circuit and includes the resistor pair and the capacitor connected in series between the positive terminal and the common terminal. A first resistor of the resistor pair and the capacitor are connected in series between the positive terminal and the negative terminal. A second resistor of the resistor pair is connected between the negative terminal and the common terminal.

[0019] In other features, the capacitor is connected across a power source and between the positive terminal and the negative terminal.

[0020] In other features, the resistor pair comprises a first resistor and a second resistor. The first resistor includes i) a first end connected to a first end of the capacitor, and ii) a second end connected to a first one of the set of input terminals and to the brush. The second resistor includes i) a first end connected to a second one of the set of input terminals, to a second end of the capacitor, and to the part, and ii) a second end connected to a third one of the set of input terminals.

[0021] In other features, the first end of the capacitor is connected to a positive terminal of a power source. The second end of the capacitor is connected to a negative terminal of the power source.

[0022] In other features, a lead is connected between i) the second of the set of input terminals, the first end of the second resistor and the second end of the capacitor and ii) one or more 3-phase contacts of the part.

[0023] In other features, the insulation testing method further comprises: converting an analog signal output from the circuit into a digital signal via an analog-to-digital converter, the analog-to-digital converter being connected to the circuit; and detecting, based on the digital signal, when a short circuit exists between the conductive element of the part and the one or more conductive bristles.

[0024] In other features, the insulation testing method further comprises generating at least one of a message or an alarm when a short circuit is detected between the conductive element of the part and the one or more conductive bristles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present disclosure will be more fully understood from the detailed description and the accompanying drawings, in which: Fig. 1 is a bottom view of a portion of a stator illustrating an exemplary defect in an insulating coating; Fig. 2 is a schematic view of an exemplary insulation testing system testing a stator and including a voltage and current balancing circuit according to the present disclosure; Fig. 3 a schematic view of the insulation testing system of Fig. 2 testing a single hairpin of a stator according to the present disclosure; and Fig. 4 illustrates an exemplary insulation testing method for detecting, marking, identifying, and reporting faults in accordance with the present disclosure.

[0026] Reference symbols may be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0027] During motor manufacturing, defects such as defects in the insulating coatings of a stator's electrical elements may be inspected. The insulating coatings may be visually inspected. This may include a quality control engineer using a magnifying glass to visually inspect for defects in the stator's insulating coatings. Such testing is labor-intensive and subject to the technician's limitations. A continuity tester may be used, which applies a voltage to the stator and detects whether a short circuit exists. An electrical current will flow between the stator and the continuity tester if there is a lack of insulating material where the tester contacts the stator.

[0028] The continuity tester may include a brush with conductive bristles. The bristles can be moved over various areas of the stator to detect short-circuit locations (i.e., defective locations) where there is a lack of insulating material. The opposite can occur if the part (or stator) is moved by the bristles and the brush remains stationary. A circuit is used to monitor voltage changes across the brush. The voltage drops sharply when a short circuit occurs. There are large voltage and current fluctuations when there is no short circuit and when there is a short circuit.

[0029] Large voltage and current fluctuations in the circuit can damage components over time if not managed properly. Thus, the components can degrade over time, which can negatively impact the circuit's operation. For example, an A / D converter may have specific voltage and current limitations based on its application. The resulting drift in circuit components such as resistors or other circuit components can lead to voltage behavior that can cause problems in setting the voltage threshold and detecting a short circuit. Deterioration of the circuit components can lead to voltage drift, which in turn can lead to subsequent defects going undetected. This drift requires circuit adjustments and periodic recalibration, including threshold adjustments.A defect can be detected when the voltage falls below the threshold. For example, the threshold can be set to 5 volts (V), which is significantly below a nominal voltage and / or a normally expected voltage (e.g., 24 V). The threshold can be set to less than or equal to 20% of the nominal voltage.

[0030] Drift can also lead to unsafe current levels. As circuit components wear over time, changing the circuit's expected current, this can result in current levels in the circuit that may exceed a threshold for perceived and / or actual physical harm. Furthermore, higher-than-expected current levels can also be harmful to parts and the brush, even if human exposure is mitigated.

[0031] The examples set forth herein include an insulation testing system having a voltage and current balancing circuit as described in Fig. 2-3. The voltage and current compensation circuit provides a balanced voltage response at a low nominal current, which is detected via the bristles of a continuity test brush used to detect a defect (or short circuit). The voltage and current compensation provides stability, improves the longevity of circuit components, and provides improved functionality, allowing the insulation test system to be used in various applications while remaining touch-safe. In addition to the hardware mentioned above, the insulation test system also includes an algorithm for marking defective parts. This algorithm improves sensitivity for better detection of defects.

[0032] The voltage and current compensation circuit improves safety flexibility by incorporating a capacitor for voltage distribution and appropriately sized resistors R1 and R2. The resistors R1 and R2 are selected to produce a low current response. The capacitor and resistors are connected to the common, negative, and positive terminals of an analog-to-digital (A / D) converter. The values ​​of resistors R1 and R2 are selected to produce a low current response during all operation and / or at all operating points of the voltage and current compensation circuit. The low current response makes the test setup safe for an operator. The capacitor produces an open circuit condition when no electrical short circuit exists. If a short circuit is detected using a brush (e.g.a brush with carbon bristles), the voltage at the positive end of the capacitor drops, resulting in some voltage drop across resistors R1 and R2, so that the voltages at each positive and negative terminal of the A / D converter remain within a predetermined voltage range (e.g., ±13 V) relative to a voltage at the common A / D terminal.

[0033] Resistors R1 and R2 are selected so that the current in the entire voltage and current compensation circuit remains below a predetermined current value in the event of a short circuit (e.g., less than or equal to 25 mA, which is imperceptible to human contact). From the perspective of an incoming analog voltage signal, this would mean that the positive terminal of the A / D converter is held at the nominal operating voltage (e.g., 24 V) and the negative terminal of the A / D converter is held at 0 V when there is no short circuit. If there is a break in the insulation, i.e., a short circuit of the connection between the brush and the phase conductor, the following changes occur in the voltage and current compensation circuit. The positive A / D terminal is pushed towards 0 V.It should be noted that the positive A / D terminal may not quite reach 0 V due to intermittent contact between the brush bristles, but in the event of a massive short circuit, the positive A / D terminal will be forced to 0 V. A defect is detected when the positive A / D terminal drops to or below a predetermined threshold (e.g., 5 V) compared to the base or no short-circuit nominal voltage (e.g., 24 V).

[0034] Since the negative A / D terminal is held at 0 V, there is a 0 V difference between the positive and negative A / D terminals, and consequently the common A / D terminal is also at 0 V. For this reason, the resistor R2, which is connected between the negative and common A / D terminals, has a voltage drop of 0 V (no current flow).

[0035] When a defect is detected, the capacitor has charge available to discharge when needed, rather than having a current source providing the rated voltage connected directly to the short circuit (or defect). This allows a constant voltage drop across the capacitor to be maintained while minimizing current flow in any one branch of the voltage and current balancing circuit, as the corresponding brush makes intermittent contact with the defect. This is achieved by maintaining a resistor-capacitor (RC) time constant long enough so that the discharge of the capacitor does not cause large fluctuations in the voltage drop across the capacitor during the period of intermittent contact between the brush and the defective area. As an example, the time constant might be 24 seconds.This results in a resistor R1 being connected between i) the capacitor and ii) the positive A / D terminal and the brush, which primarily experiences the voltage drop when a short circuit occurs.

[0036] To ensure that the current in the circuit does not exceed a value that the human body can perceive, resistor R1 is selected so that the current does not exceed a threshold value (e.g., 1 milliampere (mA)) in the event of a short circuit. This voltage and current balancing at all operating points ensures that the entire voltage and current balancing circuit is safe for humans and does not introduce current or voltage values ​​that would damage either the brush bristles or any part under test. The current and voltage levels remain below the predetermined thresholds to prevent, for example, arcing.

[0037] If a short circuit is present, the capacitor can be discharged at a reasonable rate to enable a fast, stable measurement. Current flows through the resistors and provides an analog voltage measurement for the A / D converter. Once the brush is removed from the defect and the short circuit is no longer present, the capacitor is charged until it returns to an open circuit state.

[0038] The voltage and current compensation circuit prevents damage to circuit components by preventing large voltage and current fluctuations across the circuit components in the event of a short circuit. The capacitor and resistor values ​​are selected to improve circuit performance and prevent deterioration of the circuit components due to parasitic voltages across the resistors. The values ​​are selected to prevent drift in the values ​​of circuit components. This prevents larger-than-expected voltage drops and arcing across the brush bristles.

[0039] Fig. 1 illustrates a section 100 of a stator. The stator comprises welded wire pairs coated with insulating material. The section 100 includes a defect 102 in which a portion of the insulating coating 104 is missing and the conductive material 106 of a wire is exposed. Fig. 1, a lower (or welded) end of the stator is shown. The stator comprises a laminated stack (or body) 110 having a bottom surface 112 and a plurality of ears (one ear 114 is shown in Fig. 1). As an example, the insulating coating 104 may be made of epoxy.

[0040] Fig. 2 illustrates an insulation testing system 200 testing a stator 202. The insulation testing system 200 includes a human-machine interface (HMI) 204 and a voltage and current balancing circuit 206 connected to a power source 208. The HMI 204 may include a control module 210, an A / D converter 212, a memory 214, a transceiver 216, a display 218, and an audible device 220. The display 218 includes LEDs 222 and / or other visual display and / or indicator elements. The control module 210 receives digital voltage data from the A / D converter 212, which receives an analog input signal from the voltage and current balancing circuit 206. The control module 210 detects defects when the analog output signal via the positive and negative terminals 223, 226 (or the corresponding digital signal) of the A / D converter 212 drops in voltage below the threshold value (e.g.5 V or 20% of the nominal or normally expected voltage (e.g., 24 V). The normally expected voltage when no defect is detected may be 24 V. The control module 210 may indicate the detection of defects via the display 218 and the audible device 220. The detection of a defect, the change (or decrease) in voltage, the time of detection, and / or other related information may be stored in the memory 214. For example, the detection of the defect may be stored along with the immediate position of the defect relative to one or more reference points on the stator 202.

[0041] The display 218 provides a visual aid to indicate the detection of a defect. This also provides information about when a defect is detected. The acoustic device 220 may provide a loud sound, such as a loud alarm signal, when a defect is detected. The acoustic device 220 may include, for example, a speaker. The control module 210 may report detected defects and corresponding information stored in the memory 214 to one or more network devices remote from the HMI 204 via the transceiver 216.

[0042] The voltage and current balancing circuit 206 includes resistors R1, R2, and a capacitor C. The resistor R1 has i) a first end connected to a first (or positive) terminal of the A / D converter 212 and to the brush 228, and ii) a second end connected to a first end of the capacitor C and to a positive terminal of the power source 208. The resistor R2 has i) a first end connected to the second (or negative) input terminal 226 of the A / D converter 212, a second end of the capacitor, one or more of the 3-phase contacts 224, and a negative terminal of the power source 208, and ii) a second end connected to a third (or common) terminal COM of the A / D converter 212. The common terminal COM is separate from and not connected to the terminals 223, 226.A line 225 is connected between i) the negative terminal 226, the first end of resistor R2, and the second end of capacitor C, and ii) the one or more 3-phase contacts 224. The first end of capacitor C is connected to the positive terminal of power source 208. A second end of capacitor C is connected to the negative terminal of power source 208.

[0043] Resistors R1, R2, and capacitor C are connected in series between terminal 223 and the common terminal COM. In the example shown, capacitor C is connected between resistors R1 and R2. In one embodiment, resistors R1 and R2 are connected directly to terminals 223, 226 and directly to capacitor C. Resistor R1 can be connected directly to brush 228. Resistor R2 can be connected directly to stator 202.

[0044] As an example, resistor R1 may be 20-30 kiloohms (kΩ), resistor R2 400-500 kΩ, and capacitor C 500-1500 microfarads (µF). In one embodiment, R1 is 24 kΩ, R2 470 kΩ, and C is 1000 µF. The resistances of the resistors and the capacitance of the capacitor are selected to provide the RC time constant mentioned herein. In one embodiment, resistors R1, R2 are selected to limit the current flowing through stator 202, voltage and current balancing circuit 206, and brush 228. The resistances of resistors R1 and R2 and the capacitance of capacitor C are chosen i) to avoid arcing and sparking at bristles 230 when a defect (short circuit) occurs, and ii) to ensure proper current balancing in the circuit during all test conditions to maintain safety for human contact (less than 1 mA).For example, resistors R1 and R2 may be selected so that the current through circuit 206, brush 228, and stator 202 does not exceed a predetermined threshold.

[0045] The resistor values ​​are chosen to limit the current in all operating aspects and to balance the allowable voltage load across the channels of the A / D converter 212, such as those associated with terminals 223, 226. In one embodiment, and regardless of whether a defect (short circuit) or no defect (no short circuit) is present, the current is maintained between 25 microamperes (uA) and 1 mA due to i) the arrangement and selected values ​​of resistors R1 and R2 along with capacitor C in the voltage and current balancing circuit 206 with respect to the current source 208 (e.g., 24 VDC power supply) and ii) the A / D voltage channel limits between different channels with respect to the common A / D terminal COM. The resistances of R1 and R2 can be changed based on the A / D behavior limits to maintain the described current behavior.For example, the channel limits can be selected such that the A / D channels of the A / D converter are within ±10-13 V of the common A / D terminal COM. In one embodiment, the channel limits are selected such that the A / D channels are within ±10.2 V of the common A / D terminal COM.

[0046] The capacitance of capacitor C is selected such that, in conjunction with the R1 value chosen for current level reasons, a sufficiently long RC time constant is achieved. This is done to provide a stable nominal voltage (e.g., a stable 24 V) for the voltage and current compensation circuit 208 within the time window required to determine whether a short circuit has occurred. The value of R1*C can provide a time constant of approximately 24 seconds. This provides a sufficiently long time constant that does not need to be increased further with a larger C value; however, the time constant can be increased further. If the time constant is too small, the charging and discharging behavior of capacitor C would influence the operation of the circuit in such a way that the nominal voltage would no longer remain stable at 24 V when a defect occurs.This can make it difficult to assign a specific threshold for defect detection because the voltage response is distorted by the behavior of the capacitor C.

[0047] The capacitance of capacitor C affects the rate of change of current flowing through stator 202, voltage and current balancing circuit 206, and brush 228. Capacitor C is included as protection for brush 228 and bristles 230, preventing a current surge from power source 208 to the short circuit location. When there is no short circuit, capacitor C is charged. When a short circuit exists, capacitor C discharges. Capacitor C does not fully discharge due to the RC time constant used. This helps limit the current in the circuit during a short circuit event. After discharging, power source 208 recharges capacitor C. When the bristles are moved, the short circuit typically lasts only a short time. Without capacitor C, resistors R1 and R2 can be damaged due to a short circuit and a current surge through resistors R1 and R2.The capacitance and resistance values ​​can also be selected depending on the application to provide low current consumption for safe use by operators. For example, the capacitance of capacitor C and the resistances of resistors R1, R2 can be selected to accommodate different brush head designs used to detect defects. In one embodiment, the brush is designed to have a low impedance compared to the circuit components. The insulation testing system 200 is capable of accommodating brushes of different designs.

[0048] The HMI 204 and / or the A / D converter 212 detects an analog voltage across terminals 223, 226. The A / D signal is filtered by data sampling to remove noise associated with the electrical behavior of the brush bristles. A voltage from the power source 208 is provided via capacitor C, which, in conjunction with resistor R1, provides a stable voltage to the brush 228, and one of the 3-phase contacts 224 of the stator 202 is connected to line 225. When one or more of the conductive bristles 230 come into contact with an exposed conductive element of the stator 202, current flows from one of the 3-phase contacts 224 through the stator 202 and to one or more of the bristles 230 in contact with the exposed conductive element. The 3-phase contacts 224 include three contacts, one for each phase of the 3-phase stator 202.In one embodiment, the three-phase contacts 224 are connected together so that current can flow through each of the phases of the stator 202. In another embodiment, the voltage is applied to one of the three-phase contacts 224 of the stator 202 and the brush is connected to the line 225.

[0049] The insulation testing system 200 may be used to test a crown end 240 of the stator 202 as shown, a welded end 242, and / or another portion of the stator 202. The insulation testing system 200 may also be used to test individual electrical components and / or elements, an example of which is shown in Fig. 3. The crown end 240 extends upward from a lamination stack 244. The welded end extends downward from the lamination stack 244. The bristles 230 can be moved along various components of the stator 202 to detect locations where insulating material is missing.

[0050] The insulation testing system 200 includes software and hardware with adjustable A / D voltage thresholds used to mark defects. The threshold for marking a defect can be set to 5 V, for example, but can vary for different applications. The control module 210 implements a detection algorithm that detects when the voltage at terminals 223, 226 falls below one of the A / D voltage thresholds and generates a visual and / or audible signal to mark the detected defect.

[0051] The voltage and current balancing circuit described above minimizes current at all operating points, regardless of whether a short circuit is present. The installation, selection, and arrangement of resistors and capacitors as described prevent large voltage and current fluctuations and thus component degradation over time. This keeps current levels below the thresholds associated with perceived and / or actual damage.

[0052] Fig. Figure 3 illustrates the insulation testing system 200 testing a single hairpin 300 of a stator. The insulation testing system 200 includes the HMI 204 and the voltage and current balancing circuit 206 connected to a power source 208. The human-machine interface 204 may include the control module 210, the A / D converter 212, the memory 214, the transceiver 216, the display 218, and the audible device 220. The display 218 may include the LEDs 222 and / or other visual display and / or indicator elements. The voltage and current balancing circuit 206 includes resistors R1, R2, and the capacitor C. The A / D converter 212 includes the input terminals 223, 226.

[0053] Resistor R1 has i) a first end connected to a first (or positive) terminal of A / D converter 212 and to brush 228, and ii) a second end connected to a first end of capacitor C and to a positive terminal of current source 208. Resistor R2 has i) a first end connected to the second (or negative) input terminal 226 of A / D converter 212, a second end of the capacitor, one end of hairpin 300, and a negative terminal of current source 208, and ii) a second end connected to a third (or common) terminal COM of A / D converter 212. The common terminal COM is separate from and not connected to terminals 223, 226. A line 225 is connected between i) the negative terminal 226, the first end of the resistor R2 and the second end of the capacitor C and ii) the one or more 3-phase contacts 224.The first end of capacitor C is connected to the positive terminal of current source 208. A second end of capacitor C is connected to the negative terminal of current source 208.

[0054] Resistors R1, R2, and capacitor C are connected in series between terminal 223 and the common terminal COM. In the example shown, capacitor C is connected between resistors R1 and R2. In one embodiment, resistors R1 and R2 are connected directly to terminals 223, 226 and directly to capacitor C. Resistor R1 can be connected directly to brush 228. Resistor R2 can be connected directly to hairpin 300.

[0055] The hairpin 300 may include a conductive wire coated with a dielectric material (e.g., epoxy). The bristles 230 of the brush 228 may be moved along the hairpin 300 to determine whether a portion of the conductive wire is exposed through the dielectric coating, or the hairpin 300 may be moved relative to the brush 228.

[0056] Fig. Figure 4 illustrates an insulation testing method for detecting, marking, identifying, and reporting defects. The insulation testing method implements an analysis algorithm for fault detection that includes the following operations. The operations can be performed iteratively. Operations represented by solid-lined boxes can be performed with the insulation testing system 200 of Fig. 2-3 are executed.

[0057] At 400, line 225 is connected to the part to be tested, such as the stator of a motor, a hairpin, or another electrical component or element. For example, line 225 can be enhanced with one or more 3-phase contacts of a stator. At 402, control module 210 begins monitoring the voltage at input terminals 223, 226 and thus at bristles 230 of brush 228.

[0058] At 404, the brush 228 is moved over the insulated portion of the part to be tested. This involves brushing the bristles 230 against the insulated portion such that one or more of the bristles contact an uninsulated (exposed) conductive material of the part. The exposed conductive material is subject to a voltage applied to the part by the power source 208. When one or more of the bristles 230 contact an exposed portion of the part, a short circuit is created, and the control module 210 detects the voltage drop. The short circuit produces a significant voltage drop below the threshold from a nominal (or normally expected) level. The bristles remain in contact with the part while being moved relative to the part.

[0059] At 406, the control module 210 determines whether a defect has been detected. If a defect has been detected, operation 408 is performed; otherwise, the method may terminate. A defect is detected when there is a short circuit between one or more of the bristles 230 and an exposed conductive element of the part. If the part is a stator, a short circuit may exist between one or more of the bristles 230 and an exposed wire of the stator, and thus between the one or more bristles 230 and one or more 3-phase contacts of the stator.

[0060] At 408, the control module 210 records information about the defect and indicates that a defect has been detected via one or more indicators such as the display 218, the LEDs 222, and / or the audible device 220. In one embodiment, a message is displayed via the display 218. The message may include the recorded information. In another embodiment, the message is sent from the HMI 204 to another network device via the transceiver 216. This may occur at 418. The recorded information and messages may include when the defect was detected, the voltage drop across the terminals 223, 226, how long the defect was detected, the location of the defect, etc. The defect may be detected for a short period of time depending on the size of the defect and the speed of movement of the brush relative to the part being inspected.The location of the defect may be indicated relative to one or more reference points on the part under test. In one embodiment, a technician records the location of the detected defect after seeing and / or hearing an indication that a defect has been detected. As an example, a ring may be attached to the weld end of a stator under test and may have timed indices, and / or a lamination stack of the stator may have reference points. The indices and / or reference points may be used to determine the location of the detected defect. In one embodiment, the control module 210 marks the defect by illuminating a red LED or displaying a red symbol. In another embodiment, the control module 210 marks the defect by providing an audible alarm.

[0061] At 410, the detected defect may be marked. As an example, a technician may physically mark the defect with a marker. If the brush 228 and / or bristles interfere with marking the defect, operation 410 may be performed after operation 412.

[0062] At 412, brush 228 is removed from the part. At 414, the voltage of voltage and current balancing circuit 206 returns to the nominal value.

[0063] At 416, the control module 210 stops indicating that a defect has been detected and returns one or more indicators to their normal state. For example, the audible device 220 that emits the audible notification (or alarm) turns off. The illuminated LED turns green or goes out. The displayed red symbol is replaced by a green symbol or is no longer displayed.

[0064] At 418, the control module 210 may report a defect zone in which the defect is located and / or other related information (e.g., any of the information mentioned above) on the display 218, via the audible device 220, and / or to a network device remote from the HMI 204 via the transceiver 216. This may include an indication of the location of the defect on the part, the time the defect was detected, and / or other information indicating the location of the defect.

[0065] At 420, the control module may determine whether more of the part remains to be inspected. If so, operation 402 may be performed; otherwise, the method may exit at 914.

[0066] It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure. Furthermore, although the embodiments are each described above as having certain features, any one or more of these features described with respect to one embodiment of the disclosure may be implemented with and / or combined with features of any of the other embodiments, even if this combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and interchange of one or more embodiments remains within the scope of this disclosure.

[0067] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaging," "coupled," "adjacent," "beside," "on top of," "over," "below," and "disposed." Where a relationship between first and second elements is not explicitly described as "direct" in the above disclosure, that relationship may be a direct relationship, with no other intervening elements between the first and second elements, or an indirect relationship, with one or more intervening elements (either spatial or functional) between the first and second elements.

[0068] In the figures, the direction of an arrow, as indicated by the arrowhead, generally illustrates the flow of information (such as data or instructions) of interest to the illustration. For example, if element A and element B exchange a plurality of pieces of information, but the information sent from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is sent from element B to element A. Further, for information sent from element A to element B, element B may send requests or acknowledgments for the information to element A.

[0069] For the purposes of this application, which includes the definitions below, the term "module" or the term "controller" may be replaced by the term "circuit." The term "module" may refer to, be a portion of, or include: an application-specific integrated circuit (ASIC), a digital, analog, or mixed analog / digital discrete circuit, a digital, analog, or mixed analog / digital integrated circuit, a combinational logic circuit, a field-programmable gate array (FPGA), processor circuitry (common, dedicated, or group) that executes code, memory circuitry (common, dedicated, or group) that stores code executed by the processor circuitry, other suitable hardware components that provide the described functionality, or a combination of some or all of the foregoing components, such as in a system-on-chip.

[0070] The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules connected via interface circuits. For example, multiple modules may enable load balancing. In another example, a server module (also referred to as a remote or cloud module) may perform some functions on behalf of a client module.

[0071] The term "code," as used above, may include software, firmware, and / or microcode and may refer to programs, routines, functions, classes, data structures, and / or objects. The term "common processor circuit" includes a single processor circuit that executes code from multiple modules, in part or in whole. The term "group processor circuit" includes a processor circuit that, in combination with additional processor circuits, executes code from one or more modules, in part or in whole. References to multiple processor circuits include multiple processor circuits on discrete chips, multiple processor circuits on a single chip, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination thereof.The term "shared memory circuit" encompasses a single memory circuit that stores code from multiple modules, either individually or collectively. The term "group memory circuit" encompasses a memory circuit that, in combination with additional memories, stores code from one or more modules, either individually or collectively.

[0072] The term "memory circuit" is a subset of the term computer-readable medium. As used herein, the term "computer-readable medium" does not include transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); therefore, the term "computer-readable medium" can be considered tangible and non-transitory.Non-limiting examples of a non-transitory, tangible, computer-readable medium include non-volatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0073] The devices and methods described in this application may be implemented, in part or in whole, by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions contained in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a skilled technician or programmer.

[0074] The computer programs include processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. The computer programs may also include or be based on stored data. The computer programs may include a basic input / output system (BIOS) that interacts with the hardware of the special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0075] The computer programs may comprise: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language) or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated from the source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. By way of example only, source code may be written using the syntax of languages ​​including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK and Python®.

Claims

[1] Insulation testing system (200), comprising: a set of input terminals (223, 226); a brush (228); a circuit (206) connected to the set of input terminals (223, 226), the brush (228) and a part to be tested (202), the circuit (206) comprising at least one of a pair of resistors and a capacitor; and a control module (210) configured to detect when a short circuit exists between a conductive element of the part (202) and one or more conductive bristles (230) due to the absence of insulating material on the part (202) and, as a result, the one or more conductive bristles (230) of the brush (228) contact the conductive element of the part (202), wherein: the set of input terminals (223, 226) comprises a positive terminal (223) and a negative terminal (226); the capacitor and a first resistor of the resistor pair are connected in series between the positive terminal (223) and the negative terminal (226); the set of terminals (223, 226) comprises a common terminal separate from the positive terminal (223) and the negative terminal (226); and a second resistor of the resistor pair is connected between the negative terminal (226) and the common terminal. [2] The insulation testing system (200) of claim 1, wherein: the circuit (206) is implemented as a voltage and current compensation circuit and the circuit (206) comprises the resistor pair and the capacitor connected in series between the positive terminal (223) and the common terminal. [3] The insulation testing system (200) of claim 2, wherein the capacitor is connected across a current source (208) and between the positive terminal (223) and the negative terminal (226). [4] Insulation testing system (200) according to claim 3, wherein: the first resistor comprises i) a first end connected to a first end of the capacitor, and ii) a second end connected to a first of the set of input terminals (223, 226) and to the brush (228); and the second resistor i) a first end connected to a second one of the set of input terminals (223, 226), to a second end of the capacitor and to the part (202), and ii) a second end connected to a third one of the set of input terminals (223, 226). [5] Insulation testing system (200) according to claim 4, wherein: the first end of the capacitor is connected to a positive terminal of the power source (208); and the second end of the capacitor is connected to a negative terminal of the current source (208). [6] The insulation testing system (200) of claim 5, wherein a lead is connected between i) the second of the set of input terminals (223, 226), the first end of the second resistor and the second end of the capacitor, and ii) one or more 3-phase contacts (224) of the part (202). [7] The insulation testing system (200) of claim 1, further comprising an analog-to-digital converter (212) connected to the circuit (206) and configured to convert an analog signal output by the circuit (206) into a digital signal, wherein the control module (210) is configured to detect, based on the digital signal, when a short circuit exists between the conductive element of the part (202) and the one or more conductive bristles (230). [8] The insulation testing system (200) of claim 1, wherein the control module (210) is configured to generate at least one of a message or an alarm when a short circuit is detected between the conductive element of the part (202) and the one or more conductive bristles (230).

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