Description:
Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

Field of the invention:
[0001] The present disclosure relates a Drive Control Unit (DCU) for a vehicle to detect fault at terminals and method thereof.

Background of the invention:
[0002] There are certain techniques which assess or detect loose connection of terminal based on voltage drop at by measuring voltage before and after terminal. This technique would not be suitable for system where they have addition loads connected at the terminal and can result in voltage drop. Also it depends on accuracy of measurement of voltage before and after terminal. Since no sensor can be fitted before terminal on controller for voltage measurement, this demands accurate voltage info from energy source that is battery.

[0003] According to a prior art WO20188592, an arc fault detection in a motor control unit of a vehicle and a method of operation thereof is disclosed. The subject matter described in the prior art relates to a motor control unit configured for arc fault detection in a vehicle. The motor control unit as described herein is provided with a plurality of power terminals for connection to a battery and a motor. Particularly, each power terminal of said plurality of power terminals is provided with an arc fault detection element each for detecting arc faults generated therein. More particularly, said arc fault detection elements provided are thermistors disposed within the motor control unit at said power terminals. The motor control unit thus provided with said thermistors is configured to disable the vehicle based on detection of arc fault in said power terminals by said thermistors. By providing said arc fault detection elements within the motor control unit, compactness of the motor control unit and that of the vehicle is ensured.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0005] Fig. 1 illustrates a block diagram of a Drive Control Unit (DCU) for a vehicle to detect fault at terminals, according to an embodiment of the present invention;
[0006] Fig. 2 illustrates a first path and a second path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention;
[0007] Fig. 3 illustrates a third path and a fourth path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention;
[0008] Fig. 4 illustrates a fifth path and a sixth path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention, and
[0009] Fig. 5 illustrates a flow diagram of method for determining fault at terminals of the DCU of the vehicle, according to the present invention.

Detailed description of the embodiments:
[0010] Fig. 1 illustrates a block diagram of a Drive Control Unit (DCU) for a vehicle to detect fault at terminals, according to an embodiment of the present invention. The DCU 102 comprises an inverter circuit 106 comprising pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 (shown in Fig. 2) connected in parallel to each other and are connectable across a power supply 114. A node between each of the pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 are internally connected to respective terminal 108, and the inverter circuit 106 externally connectable to a drive motor 110. The DCU 102 also comprises a controller 104 connected to the pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 to control operation of the drive motor 110, characterized in that, when the DCU 102 is in operation, the controller 104 configured to detect fault at the terminals 108 based on determination and comparison of characteristic parameter with corresponding reference value.

[0011] The DCU 102 which is also referable as a Motor Control Unit (MCU) is part of the electric or hybrid vehicle 100 such as but not limited to a two-wheeler such as motorcycle, motorbike, scooter, three-wheelers such as auto-rickshaws, a four-wheeler such as cars, snow mobiles, trucks, buses, and other vehicles 100 which makes use of DCU 102 and the drive motor 110. The controller 104 is also configured to receive signal from current sensor 112 for each phase (for example, U, V, W phase in a three phase system) of the drive motor 110. The DCU 102 is shown with five terminals, three are for phase connections to the drive motor 110 and the remaining two are battery terminals.

[0012] In accordance to an embodiment of the present invention, the controller 104 is provided with necessary signal detection, acquisition, and processing circuits. The controller 104 is the one which comprises input/output interfaces having pins or ports, the memory element (not shown) such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one processor (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold values/ranges, reference values, predefined/predetermined criteria/conditions, correction factor-based maps/table which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 104 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 104 may also comprise communication units such as transceivers to communicate through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, and the like. The controller 104 is implementable in the form of System-in-Package (SiP) or System-on-Chip (SOC) or any other known types. Examples of controller 104 comprises but not limited to, microcontroller, microprocessor, microcomputer, etc.

[0013] According to an embodiment of the present invention, the fault is at least one of an arc, a high current, and a loose connection at the terminal 108. Further, according to an embodiment, the characteristic parameter is related to at least one selected from a group comprising, phasor components of stator current or phase currents, an actual motor torque, a resistance of path, and a terminal temperature. The characteristic parameter related to the phasor components of the stator current and the corresponding reference value are at least one selectable from a set comprising a cumulative deviation in at least one phasor component of stator current with a first deviation threshold, a count of deviations in the at least one phasor component of stator current with a first threshold count, a rate of change of the at least one phasor component of the stator current with a first threshold rate, and a deviation in the at least one of magnitude and frequency on Fast Fourier Transform (FFT) values of measured phase current or the at least one phasor component of stator current with a first reference FFT values. The characteristic parameter related to the actual motor torque and corresponding reference value are at least one selectable from a set comprising a cumulative deviation of the actual motor torque from a second deviation threshold, a count of deviations of the actual motor torque with a second threshold count, a deviation in rate of change of the actual motor torque with a second threshold rate, and a deviation in at least one of magnitude and frequency of Fast Fourier Transform (FFT) values of the actual motor torque with a second reference FFT values. The resistance of the paths is at least one resistance of predetermined paths of current flow compared against respective threshold resistance value. The terminal temperature is compared against reference temperature.

[0014] According to an embodiment of the present invention, for determination of fault using at least one phasor component of the stator current as the characteristic parameter, the controller 104 configured to measure stator current through respective current sensor 112, calculate at least one phasor component of the stator current using the measured stator current, determine characteristic parameter related to the at least one phasor component of the stator current, compare the characteristic parameter with respective reference value, and detect fault based on result of the comparison. The phasor component of the stator current comprises direct axis current (Id) and a quadrature axis current (Iq) as known in the art.

[0015] According to the present invention, a working of the DCU 102 with phasor component of the stator current as characteristic parameter is explained. Consider the stator current is measured by the current sensor 112. The controller 104 derives the current Id and Iq from the measured stator current and rotor position. The controller 104 monitors the deviation of the phasor components or derived Id and Iq currents against the reference deviation and records the same at regular time interval. The time interval is configurable. Whenever the deviation is observed, the deviation is cumulatively added and when the cumulative deviation is detected to be exceeding against the first deviation threshold, the controller 104 flags the fault or detects the fault and stores in the memory element. The same is indicated to a user of the vehicle 100 through indicating means such as display, audio, haptic, light, etc. on the cluster unit or infotainment unit. Alternatively, if the number of deviation of the phasor components breaches respective first threshold count, then the controller 104 again flags as a fault and saves in the memory element. In yet another alternative, if there is deviation in rate of change of phasor components or the derived Id and Iq currents against absolute value which are based on motor speed, and against reference rate of change of Id and Iq currents which are dynamically selected based on operating point. , then the controller 104 detects a fault and saves in the memory element. In yet another alternative, the controller 104 performs FFT of the actual phasor currents and/or phasor components (which are derived Id and Iq) of the stator currents. If the magnitude and/or frequency of the FFT values deviates from the corresponding first reference FFT values, the controller 104 again detects it as a fault and saves in the memory element. The controller 104 is configurable to consider at least one characteristic parameter related to the phasor components (which are derived Id and Iq) of the stator current, i.e. either independently or combinations are possible.

[0016] According to an embodiment of the present invention, for determination of fault using the actual motor torque related characteristic parameter, the controller 104 configured to measure variables comprising current through each phase of the drive motor 110, phase voltage, DC current, DC voltage, rotor speed, , rotor position and motor design parameters like winding resistance and inductance. The controller 104 further calculates the actual motor torque as a function of the measured variables. The controller 104 is further configured to compare the characteristic parameter related to the actual motor torque with respective reference value, and determine the fault using result of the comparison.

[0017] In a working scenario, when the vehicle 100 is being driven by the driver, the controller 104 monitors the variables and calculates the actual motor torque. For example, the controller 104 compares the deviation from cumulated actual motor torque with second deviation threshold or count of the deviations of the actual motor torque with the second threshold count or deviation in rate of change of the actual motor torque with second threshold rate, and if there exists the deviation, the controller 104 detects as a fault at the terminal 108 and saves in the memory element. The controller 104 also performs FFT on the actual motor torque and compares the magnitude and/or frequency of the FFT values with second reference FFT values to detect the fault. If deviation is present, the controller 104 detects the fault and saves in the memory element.

[0018] According to an embodiment of the present invention, the Drive Control Unit (DCU) for the vehicle 100 to detect fault at the terminals 108 is disclosed. The DCU 102 comprises the inverter circuit 106 comprising pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 (shown in Fig. 2) connected in parallel to each other and are connectable across a power supply 114. The node between each of the pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 are internally connected to respective terminal 108, and the inverter circuit 106 externally connectable to the drive motor 110. The DCU 102 also comprises the controller 104 connected to the pairs of semiconductor switches Q1,Q2,Q3, Q4, Q5 and Q6 to control operation of the drive motor 110, characterized in that, temperature sensors 116 for each terminal 108 is connectable to at least one input pin/port of the controller 104 through the comparator 118. Thus, in a condition of shortage of the input pins/ports, a single input pin/port is configurable to receive a single signal from all the temperature sensors. For example, for three phase system, three temperature sensors 116 are connectable to the single input pin/port through the comparator 118.

[0019] In accordance to an embodiment of the present invention, the temperature sensor 116 is provided for the battery terminals and the controller 104 is configured to measure temperature of the battery terminal through the comparator or directly and compare with threshold temperature to detect the fault, specifically loose connection at the battery terminals.

[0020] According to an embodiment of the present invention, for determination of fault using terminal temperature as characteristic parameter, the controller 104 is interfaced with temperature sensors 116 for each terminal 108 through a comparator 118, and configured to receive a signal from the comparator 118. The signal comprises difference in temperatures measured by each temperature sensors 116. The controller 104 the configured to compare the signal with a threshold temperature value, and detect the fault based on result of the comparison.

[0021] According to an embodiment of the present invention, for determination of fault using the resistance of path as the characteristic parameter, the controller 104 configured to control ON/OFF states of the semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 in at least one predetermined paths to achieve a corresponding predetermined current flow path/sequence. The controller 104 then configured to calculate the resistance of the path based on applied voltage and current measured through the current sensor 112 for each of the at least one predetermined path. The controller 104 is further configured to compare the resistance of the path with a corresponding reference resistance as the reference value. The controller 104 then determines the fault using the result of the comparison. If the resistance of the path is greater than the reference resistance, then the fault is detected. The controller 104 is either configured to detect resistance of all the paths and then perform comparison with respective reference resistance or at least one of the resistance. The various flow path sequences are shown in Fig. 2 through Fig. 4.

[0022] Fig. 2 illustrates a first path and a second path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention. In the first path 200, the semiconductor switches Q1 and Q4 are controlled to be ON and other semiconductor switches are OFF and connected through U and V phase of the drive motor 110. The first path 200 is shown with the dashed line between two terminal of the power supply 114. Further, the controller 104 controls the state of the semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 through a Pulse Width Modulation (PWM) signal 202.

[0023] In Fig. 2, the second path 210 is also shown. Here, the semiconductor switch Q1 and Q6 are ON through U and W phase of the drive motor 110.

[0024] Fig. 3 illustrates a third path and a fourth path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention. The third path 300 involves the activated semiconductor switches Q3 and Q6 through V and W phase of the drive motor 110. Similarly, the fourth path 310 involves the activated semiconductor switches Q3 and Q2 through V and U phase of the drive motor 110. The direction of current as shown in the Figure 3 through dashed line must be taken into consideration.

[0025] Fig. 4 illustrates a fifth path and a sixth path of current flow through selected semiconductor switches and the selected phases of the drive motor, according to an embodiment of the present invention. The fifth path 400 comprises the flow of current through semiconductor switch Q5, W phase, U phase, and semiconductor switch Q2. The same is indicated by the dashed arrow. Similarly, the sixth path 410 comprises the flow of current through semiconductor switch Q5, W phase, V phase and the semiconductor switch Q4. The same is indicated by the dashed arrow.

[0026] In the Fig. 2 through Fig. 4, the controller 104 calculates the resistance of at least one of the first path 200, the second path 210, the third path 300, the fourth path 310, the fifth path 400 and the sixth path 410 either sequentially or randomly. The semiconductor switches are controlled using PWM signal 202. The controller 104 calculates the resistance till the fault is found. Alternatively, the controller 104 is configured to measure resistance for all the paths irrespective of fault is found or not. The resistance is calculated based on voltage divided by current. The voltage is detected from the applied voltage and the current is measured by the current sensor 112. If there is any deviation, the controller 104 detects fault and saves in the memory element. The fault is indicated in the vehicle 100 as mentioned before.

[0027] Fig. 5 illustrates a flow diagram of method for determining fault at terminals of the DCU of the vehicle, according to the present invention. The fault is detected when the DCU 102 is operated in connection with the drive motor 110. The DCU 102 comprises pairs of semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 connected in parallel to each other and are connectable across to power supply 114. The node between each of the pairs of semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 are internally connected to the terminals 108, and the terminals 108 are externally connectable to the drive motor 110. The method is characterized by plurality of steps, of which a step 502 comprises determining, by the controller 104, values of characteristic parameter. A step 504 comprises comparing, by the controller 104, values of the determined characteristic parameter with respective reference values. A step 506 comprises detecting, by the controller 104, the fault at the terminals 108 based on the result of the comparison.

[0028] According to the method of the preset invention, the fault is at least one of the arc, the high current, and the loose connection at the terminal 108. Further, the characteristic parameter is related to at least one selected from the group comprising, phasor components of stator current, the actual motor torque, the resistance of at least one path of the current flow, and the terminal temperature. The characteristic parameter related to the phasor components of the stator current and the corresponding reference value are at least one selectable from the set comprising the cumulative deviation in at least one phasor component of stator current with the first deviation threshold, the count of deviations in the at least one phasor component of stator current with the first threshold count, the rate of change of the at least one phasor component of the stator current with the first threshold rate, and the deviation in the at least one of magnitude and frequency on Fast Fourier Transform (FFT) values of phase currents or the at least one phasor component of stator current with the first reference FFT values. The characteristic parameter related to the actual motor torque and corresponding reference value are at least one selectable from the set comprising the cumulative deviation of the actual motor torque from the second deviation threshold, the count of deviations of the actual motor torque with the second threshold count, the deviation in rate of change of the actual motor torque with the second threshold rate, and the deviation in at least one of magnitude and frequency of Fast Fourier Transform (FFT) values of the actual motor torque with the second reference FFT values. The resistance of the paths is at least one resistance of predetermined current flow paths compared against respective threshold resistance value. The terminal temperature is compared against reference temperature.

[0029] According to the step 502, a method for determining the at least one phasor component of stator current as characteristic parameter is provided. The method comprises plurality of steps, of which a step 508 comprises measuring stator current through respective current sensor 112. A step 510 comprises calculating at least one phasor component of the stator current using the measured stator current. A step 512 comprises determining characteristic parameter related to the at least one phasor component of the stator current.

[0030] According to the step 502, a method for determining the actual motor torque related as the characteristic parameter is provided. The method comprises a step 514 comprising, measuring, by the controller 104, variables comprising current through each phase of the motor, phase voltage, DC current, DC voltage rotor speed, a rotor position and motor design parameters like winding resistance and inductance. A step 516 comprises calculating, by the controller 104, the actual motor torque as the function of the measured variables. The torque deviation is observed by the method. The controller 104 detects torque deviation resulting due to imbalanced phase currents as a function of increased resistance of the terminal 108. The torque deviation can also be impacted due to change in winding resistance. Thus to isolate the impact due to change in winding resistance, the method comprises detecting magnitude of torque deviation and comparing against reference value.

[0031] According to the step 502, a method for measuring terminal temperatures is provided. The method comprises a step 518 which comprises, receiving, at the input pin/port of the controller 104, the signal from the comparator 118 which is interfaced with temperature sensors 116 for each terminal 108. The temperature measured are compared with each other and difference is received as input by the controller 104 for further processing. In the method, a rise in temperature of terminals 108 is monitored. Firstly values of temperature sensors 116 are checked for plausibility by comparing against other sensor values. Then the controller 104 checks for gradient in rise in temperature or absolute temperature, if either of it is greater than the temperature threshold value, the controller 104 detects the terminal 108 to be of high resistance which could be due to one of reasons of fault. Once detected, the terminals 108 can be checked for loose connection or cleaning for any impurity on contact surface. The temperature is measured by mounting temperature sensors 116 onto each of terminals 108 within DCU 102 and monitored throughout operation of the DCU 102. Since each terminal’s 108 temperature sensor 116 require analog input to monitor, this is optimized using respective comparator 118 and a multiplexor if not enough analog pins available in the controller 104 or otherwise.

[0032] According to an embodiment of the present invention, a heating of the terminals 108 is possible to be detected using the current flow, which confirms/validates an abnormal raise in temperature. This is done at three different current levels (low, medium, and high) to have individual detection thresholds for three levels. Current squared through time is used to determine amount of energy flow into the drive motor 110 and to prevent it from overheating due to excessive currents during vehicle usage ) This current squared through time value indicates whether temperature rise is due to abnormal heating or due to vehicle usage.

[0033] According to the step 502, a method for determining the resistance of flow paths as the characteristic parameter is provided. The method comprises a step 520 comprising, controlling, by the controller 104, ON/OFF states of the semiconductor switches Q1, Q2 Q3, Q4, Q5 and Q6, in at least one of plural predetermined paths. A step 522 comprises calculating, by the controller 104, the resistance based on applied voltage and current measured through current sensor 112 for each of path. The resistance of current flow path is measured through selective switching of semiconductor switches (such as MOSFETs or FETs, etc.) and compared against reference resistance value. Before comparing, each of resistance values are checked for its plausibility by comparing against resistance of other resistance values. Any change in estimated resistance against the reference resistance value is considered to be in-appropriate. Based on magnitude of change in resistance value, the method, or the controller 104 ascertains and detects the fault.

[0034] According to an embodiment of the present invention, the DCU 102 and method for detection of terminal fault (such as loose connection) through the characteristic parameter comprising temperature sensing, torque deviation check, phase current and phasor components of the stator current and resistance of the path, are provided. The present invention provides solution for detection of loose connection of power terminals 108 on DCU 102, i.e. DC power terminals 108 and phase terminals, detection of rise in temperature on terminals 108 due to increased contact resistance caused by loose connection, and detection of change in resistance of current flow path between terminals 108 by selective switching of semiconductor switches Q1, Q2, Q3, Q4, Q5 and Q6 such as MOSFETs. The present invention enables early detection of loose connection of terminals 108 and other faults. The characteristic parameters considered by the DCU 102 uses existing/available sensors in the drive motor 110, no additional/external sensors are provided/needed. The characteristic parameter are usable either alone or conjunction with each other for robustness.

[0035] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.
, Claims:We claim:
1. A Drive Control Unit (DCU) (102) for a vehicle (100) to detect fault at terminals (108), said DCU (102) comprises:
an inverter circuit (106) comprising pairs of semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) connected in parallel to each other and are connectable across a power supply, a node between each of said pairs of semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) are internally connected to respective terminal (108), said inverter circuit (106) externally connectable to a drive motor (110), and
a controller (104) connected to said pairs of semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) to control operation of said drive motor (110), characterized in that, when said DCU (102) is in operation, said controller (104) configured to detect fault at said terminals (108) based on determination and comparison of characteristic parameter with corresponding reference value.

2. The DCU (104) as claimed in claim 1, wherein said fault is at least one of an arc, high current and a loose connection at said terminals (108), and wherein said characteristic parameter is related to at least one selected from a group comprising phase current or phasor components of stator current, an actual motor torque, a resistance of flow path and a terminal temperature, wherein said characteristic parameter related to said phasor components of stator current and said corresponding reference value are at least one selectable from a set comprising a cumulative deviation in at least one phasor component of stator current with a first deviation threshold, a count of deviations in said at least one phasor component of stator current with a first threshold count, a rate of change of said at least one phasor component of stator current with a first threshold rate, and a deviation in said at least one of magnitude and frequency on Fast Fourier Transform (FFT) values of said phase current or at least one phasor component of stator current with a first reference FFT values, wherein said characteristic parameter related to said actual motor torque is and corresponding reference value are at least one selectable from a set comprising a cumulative deviation of said actual motor torque from a second deviation threshold, a count of deviations of said actual motor torque with a second threshold count, a deviation in rate of change of said actual motor torque with a second threshold rate, and a deviation in at least one of magnitude and frequency of Fast Fourier Transform (FFT) values said actual motor torque with a second reference FFT values, wherein said resistance of flow paths is at least one resistance of predetermined sequence of current flow paths compared against respective threshold resistance.

3. The DCU (102) as claimed in claim 2, wherein for determination of fault using at least one phasor component of stator current as characteristic parameter, said controller (104) configured to
measure stator current through respective current sensor (112);
calculate at least one phasor component of said stator current using said measured stator current;
determine characteristic parameter related to said calculated at least one phasor component of said stator current;
compare said characteristic parameter with respective reference value, and
detect fault based on result of said comparison.

4. The DCU (102) as claimed in claim 2, wherein determination of fault using said actual motor torque related characteristic parameter, said controller (104) configured to
measure variables comprising current through each phase of said drive motor, phase voltage, DC current, DC voltage, rotor speed rotor position and motor design parameters like winding resistance;
calculate said actual motor torque as a function of said measured phase current, phase voltage, DC current, DC voltage, rotor speed rotor position, and motor design parameters like winding resistance;
compare said characteristic parameter related to said actual motor torque with respective reference value, and
determine said fault using result of said comparison.

5. The DCU (102) as claimed in claim 2, wherein for determination of fault using terminal temperature as characteristic parameter, said controller (104) is interfaced with temperature sensors (116) for each terminal (108) through a comparator (118), and configured to
receive a signal from said comparator (118), said signal comprises difference in temperatures measured by each temperature sensors (116);
compare said signal with a threshold temperature value, and
determine a fault based on result of said comparison.

6. The DCU (102) as claimed in claim 2, wherein for determination of fault using said resistance of paths as said characteristic parameter, said controller (104) configured to
control ON/OFF states of said semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) in at least one predetermined paths;
calculate said resistance of path based on applied voltage and current measured through a current sensor (112) for each of said at least one predetermined path;
compare said resistance of path with a reference resistance as said reference value, and
determine a fault using result of said comparison.

7. A method for detecting a fault at terminals (108) of a Drive Control Unit (DCU) (102) when operated in connection with a drive motor (110), said DCU (102) comprises pairs of semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) connected in parallel to each other and are connectable across to power supply, a node between each of said pairs of semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) are internally connected to said terminals (108), and said terminals (108) are externally connectable to said drive motor (110), characterized by, said method comprising the steps of:
determining values of characteristic parameter;
comparing values of said determined characteristic parameter with respective reference values, and
detecting a fault at said terminals (108) based on the result of said comparison.

8. The method as claimed in claim 6, wherein said fault is at least one of an arc, high current and a loose connection at said terminals (108), and wherein said characteristic parameter is related to at least one selected from a group comprising phase current or phasor components of stator current, an actual motor torque, a resistance of paths and a terminal temperature, wherein said characteristic parameter related to said phasor components of stator current and said corresponding reference value are at least one selectable from a set comprising a cumulative deviation in at least one phasor component of stator current with a first deviation threshold, a count of deviations in said at least one phasor component of stator current with a first threshold count, a rate of change of said at least one phasor component of stator current with a first threshold rate, and a deviation in said at least one of magnitude and frequency on Fast Fourier Transform (FFT) values of said phase current or at least one phasor component of stator current with a first reference FFT values, wherein said characteristic parameter related to said actual motor torque is and corresponding reference value are at least one selectable from a set comprising a cumulative deviation of said actual motor torque from a second deviation threshold, a count of deviations of said actual motor torque with a second threshold count, a deviation in rate of change of said actual motor torque with a second threshold rate, and a deviation in at least one of magnitude and frequency of Fast Fourier Transform (FFT) values said actual motor torque with a second reference FFT values, wherein said resistance of path is at least one resistance of predetermined path of current flow compared against respective threshold resistance.

9. The method as claimed in claim 7, wherein for determining said at least one phasor component of stator current as characteristic parameter, said method comprises the steps of:
measuring stator current through respective current sensor (112);
calculating at least one phasor component of said stator current using said measured stator current, and
determining characteristic parameter related to said at least one phasor component of said stator current.

10. The method as claimed in claim 7, wherein for determining said actual motor torque related as characteristic parameter, said method comprises the steps of,
measuring variables comprising current through each phase of said drive motor (110), phase voltage, DC current, DC voltage, rotor speed, rotor position, and motor design parameters like winding resistance, and
calculating said actual motor torque as a function of said measured phase current, phase voltage, DC current, DC voltage rotor speed, rotor position and motor design parameters like winding resistance.

11. The method as claimed in claim 7, wherein for measuring terminal temperatures, said method comprises receiving, at an input pin/port of said controller (104), a signal from a comparator (118) which is interfaced with temperature sensors (116) for each terminal (108), wherein temperature measured are compared with each other and difference is received as input by said controller (104).

12. The method as claimed in claim 7, wherein for determining said resistance of path as characteristic parameter, said method comprises the steps of:
controlling ON/OFF states of said semiconductor switches (Q1, Q2, Q3, Q4, Q5, Q6) in at least one of predetermined path, and
calculating said terminal resistance based on applied voltage and current measured through current sensor (112) for each of predetermined path.