DESC:METHOD FOR INSULATION DETECTION OF MOTOR DRIVE
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202421021040 filed on 19/03/2024, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
The present disclosure generally relates to a motor drive. Particularly, the present disclosure relates to a method for insulation detection of a motor drive.
BACKGROUND
The electric vehicle (EV) market is rapidly expanding, driven by advancements in battery technology, government incentives, and increasing environmental concerns. Recently, the motor drive system in electric vehicles has evolved with advancements in power electronics, control algorithms, and efficiency optimization. The modern electric and hybrid vehicles utilize high-efficiency inverters and advanced motor designs like PMSM and induction motors. Also, the emerging trends include SiC and GaN-based inverters for reduced losses and higher power density. However, with increasing usage of motor drive in vehicles, the insulation problems in the motor drive arises. The insulation problems in the motor drive occur due to factors such as electrical stress, thermal degradation, mechanical vibrations, and environmental conditions like moisture or contaminants. Over time, high-voltage stress may cause insulation breakdown, leading to leakage currents and reduced system efficiency. Also, excessive heat from prolonged operation accelerates material aging, weakening insulation properties. Furthermore, the mechanical shocks and continuous vibrations may create microcracks in insulating layers, increasing the risk of failure. Additionally, dust, humidity, and chemical exposure can degrade insulation surfaces, leading to unintended short circuits or safety hazards.
Traditionally, the isolation in the motor drives of electric vehicles traditionally monitored using resistance-based measurement techniques, voltage monitoring methods, and insulation resistance testers. These methods primarily relied on measuring the insulation resistance between the high-voltage (HV) system and the vehicle chassis to detect any potential faults or degradation in isolation. One of the common technique is resistance measurement method, where a high-value resistor is connected between the HV bus and the chassis ground. By applying a known voltage and measuring the leakage current, the insulation resistance is calculated. If the resistance dropped below a predefined threshold, an isolation fault is detected. However, the method has significant drawbacks. Firstly, these method required additional passive components that added to the system complexity and cost. Secondly, the method may not detect dynamic isolation failures, such as insulation breakdown occurring due to transient voltage spikes or mechanical stress over time. Moreover, during operation, insulation degradation is often gradual and not easily captured by periodic resistance measurements, leading to potential undetected faults. Another conventional approach involved voltage-based monitoring, where the voltage difference between the HV system and the chassis ground is continuously observed. Any unexpected fluctuations in the voltage difference may be indicate a loss of isolation. While the method is relatively straightforward, but the method suffered from low sensitivity to minor faults, making the method ineffective in detecting early-stage insulation degradation. Additionally, the method prone to false positives due to external noise, temperature variations, or minor fluctuations in the high-voltage system, leading to unnecessary warnings or system shutdowns. Moreover, a more manual method is often used which is the insulation resistance test using a megohmmeter, where a high DC voltage (e.g., 500V to 1000V) is applied to the motor drive circuit while the vehicle is off, and the resulting leakage current is measured to determine insulation integrity. This method is highly effective in detecting severe insulation breakdowns but not impractical for real-time monitoring, as the method required the vehicle to be taken offline for testing. Moreover, the method may be only detecting the insulation failures that had already occurred and is not effective in predicting insulation degradation over time.
Therefore, there is a need to provide an improved technique for isolation detection in a motor drive of an electric vehicle to overcome one or more problems associated as set forth above.
SUMMARY
An object of the present disclosure is to provide a method for insulation detection of a motor drive.
In accordance with an aspect of the present disclosure, there is provided a method for insulation detection of a motor drive. The method comprises powering up the motor drive in idle condition, implementing a short circuit and sampling a signal with a current sensing element and a DC loop.
The present disclosure provides the method for insulation detection of the motor drive. The method as disclosed by present disclosure is advantageous in terms of enhanced reliability by enabling early detection of insulation degradation through leakage current measurement and insulation resistance evaluation. Beneficially, the method ensures accurate assessment of insulation health, thereby minimizing unexpected failures. Furthermore, the method allows seamless monitoring without requiring additional external equipment. Beneficially, the method provides a precise current measurement, thereby improving the diagnostic accuracy. Beneficially, the method generates automated alert which significantly enhances the safety by notifying users of insulation issues in real-time. Additionally, the method advantageously facilitates the predictive maintenance and extending the lifespan of motor drive systems.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 illustrates a flow chart of a method for insulation detection of a motor drive, in accordance with an aspect of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a method for insulation detection of a motor drive and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the terms “electric vehicle”, “EV”, and “EVs” are used interchangeably and refer to any vehicle having stored electrical energy, including the vehicle capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source. Additionally, it is to be understood that the ‘electric vehicle’ as used herein includes electric two-wheeler, electric three-wheeler, electric four-wheeler, electric pickup trucks, electric trucks and so forth.
As used herein, the term “insulation detection” refers to a process or method for assessing the integrity of electrical insulation in a system, such as a motor drive, by measuring parameters indicative of insulation degradation or failure. The insulation detection process typically involves the monitoring leakage currents, insulation resistance, or other electrical characteristics to detect faults, breakdowns, or deteriorations in the insulation material. Insulation detection methods may employ current sensing elements, voltage application techniques, or diagnostic circuits to ensure reliable operation, prevent electrical hazards, and enable predictive maintenance of the system.
As used herein, the terms “motor drive” refers to a system comprising power electronics, control circuitry, and associated components configured to regulate the operation of an electric motor by controlling parameters such as voltage, current, and frequency to achieve desired motor performance characteristics.
As used herein, the term “idle condition” refers to a state in which a system, device, or component is powered on but not actively performing its primary operational function. Specifically, for a motor drive, idle condition may denote a state where the motor drive is energized, and control circuitry is active, but the motor itself is not generating torque, rotating, or driving a load.
As used herein, the term “short circuit” refers to a condition in an electrical circuit where a low-resistance path is intentionally or unintentionally created between two points, allowing current to flow in an unintended manner. The short circuit may be implemented in a controlled manner using switching elements or other circuit components to facilitate measurement, testing, or diagnostic operations without causing damage to the system.
As used herein, the term “current sensing element” refers to a component or circuit configured to detect, measure, or monitor the flow of electrical current in a conductor or circuit. The current sensing element generates an output signal corresponding to the measured current, which can be used for further analysis, control, or protection of electrical systems. The current sensing element may include, but is not limited to, current transformers, shunt resistors, Hall-effect sensors, Rogowski coils, or other sensing devices that operate based on electromagnetic, resistive, or other measurement principles.
As used herein, the term “DC loop” refers to a closed-circuit path configured to facilitate the measurement of direct current (DC) flow within a system, wherein the DC loop enables detection of insulation breakdown by monitoring leakage currents or variations in resistance indicative of insulation degradation.
As used herein, the term “leakage current” refers to an unintended electric current that flows through an insulation medium or along an undesired conductive path due to imperfections, aging, or breakdown of insulation materials. In the context of electrical systems, leakage current can occur between conductive elements and ground or between circuit components that are supposed to be electrically isolated. This current is typically small but can indicate insulation degradation, posing potential safety hazards or affecting system performance. Leakage current measurement is commonly used for monitoring insulation integrity and detecting faults in electrical and electronic systems.
As used herein, the term “insulation degradation” refers to the progressive deterioration of the electrical insulation material in a system, resulting in reduced dielectric strength and increased leakage current. The insulation degradation can be caused by factors such as thermal stress, electrical stress, mechanical wear, contamination, moisture ingress, or aging.
As used herein, the term “insulation resistance” refers to the electrical resistance offered by an insulating material between conductive components or circuits, preventing unintended current leakage. The insulation resistance quantifies the material’s ability to resist electrical conduction and is typically measured in ohms (O) or megohms (MO). Insulation resistance is a critical parameter for assessing insulation integrity, identifying degradation due to aging, contamination, or mechanical stress, and ensuring electrical safety and system reliability.
As used herein, the term “sampled signal” refers to an electrical signal that has been measured, captured, or acquired at specific intervals or instances for analysis or processing. The sampled signal generally implies that the signal is obtained using a sensing or measurement mechanism, such as a current sensor, voltage sensor, or other detection circuitry, to extract relevant electrical parameters.
As used herein, the term “predetermined threshold” refers to a predefined reference value or limit set based on empirical data, industry standards, or specific design considerations, against which a measured parameter is compared to determine a condition or trigger an action. It is typically established before operation and remains fixed or adjustable based on system requirements.
As used herein, the term “monitoring circuitry” refers to an electrical circuit or system designed to observe, measure, and analyze specific parameters of a device or system in operation. The monitoring circuitry may include sensors, amplifiers, filters, processors, comparators, memory units, and communication interfaces configured to detect, process, and report conditions such as voltage, current, resistance, temperature, or insulation integrity. The circuitry may be implemented using analog, digital, or mixed-signal components and may function autonomously or in conjunction with a control system to trigger alerts, log data, or initiate corrective actions based on predefined thresholds.
As used herein, the term “frequency converter” refers to an electrical device configured to modify the frequency of an input electrical signal to a desired output frequency, typically for controlling the speed and operation of an electric motor. The frequency converter may comprise power electronic components, such as rectifiers, inverters, and switching elements, to facilitate the conversion process. The frequency converter may operate in various modes, including AC-AC, AC-DC-AC, or DC-AC conversion, depending on the application.
As used herein, the term “current transformer” refers to a sensor device configured to measure alternating current (AC) by transforming a high primary current into a proportional lower secondary current for monitoring, protection, or control applications. The current transformer comprises a primary winding, a magnetic core, and a secondary winding, wherein the primary winding carries the current to be measured, inducing a corresponding current in the secondary winding based on the transformer's turns ratio.
As used herein, the term “closed-circuit path” refers to an electrically conductive loop that forms a continuous path for current flow, wherein the path is configured to enable controlled measurement, detection, or regulation of electrical parameters within a system."
As used herein, the term “alert signal” refers to a signal generated by a system or device in response to a detected condition, such as insulation degradation, wherein the signal may be in the form of an electrical signal, visual indicator, audible alarm, or a data transmission to a monitoring system to notify a user or control system of the detected condition
As used herein, the term “controlled short circuit condition” refers to a deliberate and regulated electrical connection between two or more circuit points, created using predefined switching elements or components within a system to facilitate specific diagnostic, testing, or protective functions. Unlike an unintended short circuit, which can cause system damage or failure, a controlled short circuit is carefully managed by controlling parameters such as voltage, current, and duration to ensure safe operation.
As used herein, the term “historical insulation resistance values” refers to previously recorded insulation resistance measurements of a motor drive system, stored over time for tracking changes in insulation health. The historical values represent a chronological dataset that allows for trend analysis, enabling the detection of gradual insulation degradation. By comparing current insulation resistance values with historical data, the system can predict potential failures, optimize maintenance schedules, and enhance reliability.
As used herein, the term “memory” refers to an electronic or digital storage component configured to store data, instructions, or historical records related to the operation of a system. It can encompass volatile memory (e.g., RAM) and non-volatile memory (e.g., ROM, EEPROM, flash memory) and may be used for storing parameters, recorded measurements, program instructions, or operational history.
As used herein, the term “degradation trends” refers to the progressive changes in a parameter over time that indicate a decline in performance, structural integrity, or functional efficiency of a system or component. The degradation trends typically relate to the systematic monitoring, recording, and analysis of variations in measurable attributes such as insulation resistance, leakage current, or other operational parameters to detect patterns that signify deterioration.
Figure 1, in accordance with an embodiment describes a method 100 for insulation detection of a motor drive. The method 100 starts at step 102 and completes at step 106. At step 102, the method 100 comprises powering up the motor drive in idle condition. At step 104, the method 100 comprises implementing a short circuit. At step 106, the method 100 comprises sampling a signal with a current sensing element and a DC loop.
The present disclosure provides the method 100 for insulation detection of the motor drive. The method 100 for as disclosed by present disclosure is advantageous in terms of enhanced reliability, safety, and efficiency of motor drive systems. Beneficially, by powering up the motor drive in an idle condition, the method 100 ensures that insulation testing may be performed without interrupting active operations which enables the predictive maintenance without affecting normal functionality. Furthermore, the implementation of a short circuit using switching elements of the frequency converter beneficially allows for a controlled test scenario, ensuring accurate insulation assessment without requiring external circuitry, thereby simplifying the system design. Beneficially, the sampled signals using a current sensing element, such as a current transformer, and a DC loop enables precise leakage current measurements, which are indicative of insulation degradation, thereby ensuring early fault detection. Additionally, the ability to determine an insulation resistance value and compare the value against a predetermined threshold further enhances fault identification accuracy, allowing for real-time condition monitoring. Moreover, the integration of monitoring circuitry at input terminals of the frequency converter significantly facilitates the continuous assessment of insulation health without requiring additional intrusive modifications to the system. Moreover, the inclusion of a memory to store historical insulation resistance values enables trend analysis, providing valuable insights into insulation degradation over time, which supports predictive maintenance strategies. advantageously, generating an alert signal upon detecting insulation degradation enhances the system safety by prompting timely intervention, minimizing the risk of failures that could lead to hazardous conditions.
In an embodiment, sampling the signal comprises measuring a leakage current indicative of insulation degradation. Upon powering up the motor drive in the idle condition, the controlled short circuit may be implemented using switching elements of the frequency converter. The current sensing element, such as the current transformer, and a DC loop are employed to measure the resulting leakage current. The leakage current serves as an indicator of insulation health, as an increased current flow suggests a breakdown or deterioration in insulation resistance. The measured leakage current may be analyzed to determine insulation resistance and compared against predefined thresholds to assess degradation levels. Beneficially, the leakage current measurement enables the real-time detection of insulation faults, thereby ensures the proactive maintenance and enhanced system reliability.
In an embodiment, the method 100 comprises determining an insulation resistance value based on the sampled signal. The controlled short circuit may be implemented using the switching elements of the frequency converter, creating a test condition that facilitates insulation evaluation. The current sensing element, such as a current transformer, along with a DC loop, may be used to sample the signal, capturing leakage current characteristics. The sampled signal may be then processed to calculate the insulation resistance value, which serves as a key indicator of the insulation condition of the motor drive system. Beneficially, the insulation resistance value provides quantitative data that may be further analyzed to assess insulation integrity, thereby enables the real-time monitoring and early detection of potential insulation breakdown.
In an embodiment, the method 100 comprises comparing the determined insulation resistance value with a predetermined threshold value to detect insulation degradation. The insulation resistance value may be computed based on the leakage current measurements and the measured values compared against the predefined threshold value. If the computed insulation resistance falls below the threshold, the method 100 indicative of insulation degradation, triggering the fault condition. Beneficially, the method 100 enables continuous and real-time monitoring of insulation health, allowing for early fault detection and preventive maintenance actions, thereby enhancing system reliability and safety.
In an embodiment, the method 100 comprises connecting monitoring circuitry to input terminals of the frequency converter. The monitoring circuitry may be designed to detect leakage currents and insulation resistance variations in real-time, ensuring proactive identification of insulation degradation. The configuration for monitoring circuitry allows the system to capture and analyze electrical characteristics at the input stage of the frequency converter, thereby improving diagnostic accuracy. Beneficially, by integrating the monitoring circuitry at the input terminals, the method 100 eliminates the need for additional external sensors, reducing complexity and cost. Furthermore, the setup ensures that insulation faults may be detected at an early stage, enabling timely maintenance interventions and enhancing the overall reliability and safety of the motor drive system.
In an embodiment, the current sensing element comprises a current transformer. Furthermore, the DC loop comprises a closed-circuit path configured to measure DC current flow indicative of insulation breakdown. The current transformer may be strategically placed within the circuit to measure leakage currents, providing real-time data indicative of insulation degradation. Simultaneously, the DC loop may be implemented as a closed-circuit path configured to detect and measure DC current flow, which serves as a direct indicator of insulation breakdown. By leveraging the current sensing element and the DC loop, the system ensures precise and continuous monitoring of insulation resistance, allowing for early detection of potential faults. Beneficially, the current sensing element and the D loop significantly enhances the safety by enabling proactive maintenance and minimizing the risk of unexpected insulation failures in motor drive systems.
In an embodiment, the method 100 comprises generating an alert signal when insulation degradation is detected. The method determines the insulation resistance value based on the sampled signal and compares the insulation resistance value to the predetermined threshold. If the insulation resistance falls below the threshold, indicating degradation, the system generates the alert signal. The alert may be transmitted to the monitoring system, a control unit, or a user interface to notify operators of potential insulation failure. Beneficially, the alert mechanism ensures timely maintenance actions, preventing further deterioration and reducing the risk of electrical faults or system downtime.
In an embodiment, implementing the short circuit comprises utilizing switching elements of the frequency converter to create a controlled short circuit condition. After powering up the motor drive in the idle state, the method 100 configures the switching elements such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs) within the frequency converter to create the short circuit condition in the controlled manner. The controlled short circuit facilitates the flow of a test current through the motor drive system without causing unintended damage or operational disturbances. The response of the system to this induced condition is then monitored using a current sensing element and a DC loop, enables the detection of leakage currents indicative of insulation degradation. By utilizing the existing switching elements within the frequency converter, the approach eliminates the need for external short-circuiting components, thereby reducing hardware complexity while ensuring accurate and reliable insulation fault detection.
In an embodiment, the method 100 comprises storing historical insulation resistance values in a memory to track degradation trends over time. By periodically sampling the insulation resistance and storing the values, the system may be analyze the long-term variations, identifying gradual degradation patterns that may indicate potential insulation failure. The historical data allows predictive maintenance strategies to be employed, ensuring that corrective actions are to be taken before critical failures occur. Additionally, the stored values can be used for comparative analysis, enabling the system to differentiate between transient anomalies and consistent degradation trends. Beneficially, the approach enhances the reliability of insulation monitoring by providing a data-driven method to assess insulation performance and schedule maintenance proactively.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combination of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
,CLAIMS:WE CLAIM:
1. A method (100) for insulation detection of a motor drive, wherein the method (100) comprises:
- powering up the motor drive in idle condition;
- implementing a short circuit; and
- sampling a signal with a current sensing element and a DC loop.
2. The method (100) as claimed in claim 1, wherein sampling the signal comprises measuring a leakage current indicative of insulation degradation.
3. The method (100) as claimed in claim 1, wherein the method (100) comprises determining an insulation resistance value based on the sampled signal.
4. The method (100) as claimed in claim 3, wherein the method (100) comprises comparing the determined insulation resistance value with a predetermined threshold value to detect insulation degradation.
5. The method (100) as claimed in claim 1, wherein the method (100) comprises connecting monitoring circuitry to input terminals of the frequency converter.
6. The method (100) as claimed in claim 1, wherein the current sensing element comprises a current transformer.
7. The method (100) as claimed in claim 1, wherein the DC loop comprises a closed-circuit path configured to measure DC current flow indicative of insulation breakdown.
8. The method (100) as claimed in claim 1, wherein the method (100) comprises generating an alert signal when insulation degradation is detected.
9. The method (100) as claimed in claim 1, wherein implementing the short circuit comprises utilizing switching elements of the frequency converter to create a controlled short circuit condition.
10. The method (100) as claimed in claim 1, wherein the method (100) comprises storing historical insulation resistance values in a memory to track degradation trends over time.