FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
"A CONTROL SYSTEM FOR OVERLOAD PROTECTION IN ELECTRIC VEHICLES AND A METHOD THEREOF"
ELECTROTHERM (INDIA) LTD, an Indian Company, of 72, Palodia, Via Thaltej, Ahmedabad 382 115, India
The following specification particularly describes the invention and the manner in which it is to be performed.

FIEED OF THE INVENTION
The present invention relates to a control system and a method for overload protection in controller of electric vehicles. In particular, the present invention relates to overcurrent protection for controller of brushless direct current (BLDC) motor in electric vehicles.
BACKGROUND OF THE INVENTION
Electric vehicles are emerging very fast in India for covering short distance. The control systems used in the electric vehicles should give reliable operation in any overload conditions. According to conventional systems, there-"is no protection available against the overload conditions integrated with the temperature rise in controllers for electric two wheelers.
During normal running of a vehicle on plain road or at a specified weight, the controller along with BLDC motor does not require high current. But once the vehicle is overloaded or the vehicle is run on a gradient, the controller and the BLDC motor take high current. The frequent supply of high current to the controller and the BLDC motor may result in rise of heat sink temperature of controller. It is therefore necessary to ensure that heat sink temperature does not go beyond specified limit for reliable operation of control system in any overload conditions, thus avoiding controller failure.
Therefore, in order to overcome the above said drawbacks, there is a need to provide a control system and a method for balancing and protecting the overload condition in electric vehicles.
OBJECTS OF THE INVENTION-/
The primary object of the present invention is to provide a control system and a method for protecting overload conditions in controller of an electric vehicle.
Another object of the present invention is to protect failure of controller under severe gradient conditions.

SIMMARY OF THE INVENTION
Accordingly, the present invention Telates to a control system for protecting overload conditions in controller of electric vehicles having a brushless direct current (DC) motor. Said control system comprising a microcontroller, a temperature sensor for measuring an instant temperature of the controller, and a current sensor for measuring an instant current drawn by the motor, wherein said microcontroller comprises a comparator circuit configured to issue a first signal based on comparison of the instant temperature of the controller with a maximum/minimum predetermined temperature of the controller, an over current detection circuit configured to issue a second signal based on comparison of the instant current drawn by motor with a predetermined current limit of the controller, and a cut-off circuit for restricting supply of current to the motor based upon issuance of said first and second signal.* _-.
Further, the present invention relates to a method for protecting overload conditions in controller of electric vehicles having a brushless DC motor, said method comprising the steps of measuring an instant temperature of the controller by a temperature sensor , measuring an instant current drawn by the motor by a current sensor, comparing the instant temperature of the controller with a maximum/minimum predetermined temperature of the controller and issuing a first signal based on said comparison, comparing the instant current drawn by the motor with a predetermined current limit of the controller and issuing a second signal based on said comparison, starting and stopping the motor alternatively and producing an ON/OFF signal based upon issuance of said first and second signal, and restricting supply of current to said motor based upon issuance of said first and second signal.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a schematic diagram of a control system of a BLDC motor according to an aspect of the present invention.
Figure 2 illustrates a flow chart showing a set of instructions embedded in microcontroller for overload protection according to an aspect of the present invention.

Figmer 3 illustrates a voltage and current waveform of 3-phase BLDC motor according to an aspect of the present invention.
Figure 4 illustrates a graph showing three minute overcurrent protection and over temperature protection according to an aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a control system and a method for overload protection in controller of electric vehicles. In particular, the present invention relates to overcurrent protection! for controller of brushless direct current (BLDC) motor in electric vehicles.
Accordingly, the present invention relates to a control system for protecting overload conditions in controller of electric vehicles having a brushless direct current (DC) motor, said control system comprising a microcontroller, a temperature sensor for measuring an instant temperature of the controller, a current sensor for measuring an instant current drawn by the motor, wherein said microcontroller comprises a comparator circuit configured to issue a first signal based on comparison of the instant temperature of the controller with a maximum/minimum predetermined temperature of the controller, an overcurrent detection circuit configured to issue a second signal based on comparison of the instant current drawn by motor with a predetermined current limit of the motor, and a cut-off circuit for restricting supply of current to the motor based upon issuance of said first and second signal.
In one aspect of the present invention, the comparator circuit issues the first signal when the instant temperature is determined to be greater than the maximum predetermined temperature.
In another aspect of the present invention, the overcurrent detection circuit issues the first signal when the instant current is determined to be greater than a predetermined current limit.
In yet another aspect of the present invention, the control system comprises one or more timers.

In US! another aspect of the present invention, the comparator circuit and overcurrent circuit are configured to repeat comparison operations for a predefined interval of time set by a first timer.
In another aspect of the present invention, the microcontroller is configured with an output signal to alternatively start and stop the motor and produce an ON/OFF signal for a predefined interval of time set by a second timer.
In yet another aspect of the present invention, supply of current to the motor is restricted for a predefined interval of time set by a third timer.
In still another aspect of the present invention, the microcontroller is configured with an output
signal to restart the motor and stop and reset at> least one timer after expiry of the predefined
interval of time set by the third timer. ' "
In another aspect of the present invention, the microcontroller is further configured to stop and reset the at least one timer when said first current is determined to be lesser than the predetermined current limit.
In yet another aspect of the present invention, the microcontroller is operatively connected to the brushless DC motor through a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) bridge circuit enabled by a MOSFET driver.
In still another aspect of the present invention, the microcontroller is operatively connected to the temperature sensor and the current sensor.
Further, the present invention relates to a method for protecting overload conditions in controller of electric vehicles having a brushless DC motor, said method comprising the steps of measuring an instant temperature of the controller by a temperature sensor , measuring an instant current drawn by the motor by a current sensor, comparing the instant temperature of the controller with a maximum/minimum predetermined temperature of the controller and issuing a first signal based on said comparison, comparing the instant current drawn by the motor with a

pr&ifcftermined current limit of the controller and issuing a second signal based on said comparison, starting and stopping the motor alternatively and producing an ON/OFF signal based upon issuance of said first and second signal, and restricting supply of current to said motor based upon issuance of said first and second signal.
In another aspect of the present invention, the first signal is issued when the instant temperature is determined to be greater than the maximum predetermined temperature.
In yet another aspect of the present invention, the second signal is issued when the instant current is determined to be greater than the predetermined current limit for a predetermined duration.

In still another aspect of the present invention, comparing the instant temperature/current with the predetermined temperature/current limit for a predefined interval of time set by a first timer.
In another aspect of the present invention, starting and stopping the motor alternatively and producing an ON/OFF signal for a predefined interval of time set by a second timer.
In yet another aspect of the present invention, restricting supply of current to the motor upon determination of the instant temperature of the controller to be greater than the maximum predetermined temperature.
In still another aspect of the present invention, restricting supply of current to the motor upon
determination of the instant current drawn by the motor to be greater than the predetermined
current limit and the instant temperature of the controller to be greater than the maximum
predetermined temperature. -/
In another aspect of the present invention, wherein restarting the motor upon determination of the instant temperature of the controller to be less than the minimum predetermined temperature.
In yet another aspect of the present invention, wherein restricting supply of current to the motor for predefined interval of time set by a third timer upon determination the instant temperature of

the^fehtroller to be less than the maximum predetermined temperature and instant current drawn by the motor to be greater than the predetermined current limit and restarting the motor thereafter.
In still another aspect of the present invention, setting the predetermined temperature within the rangeof70-120°C.
In another aspect of the present invention, setting the predetermined current limit within the range of 30A±1A.
An electric vehicle with a BLDC motor is run on power supply from a battery. If the electric vehicle is overloaded or if the vehicle is run on a gradient, the BLDC motor will be required to generate certain amount of torque. The increase in torque will cause an increase in current. If the current is not controlled, excessive torque will be available, which shall draw heavy current. Thus, the overload or overcurrent may result in failure of controller. There is also a danger that motor windings may get damaged as a result of overload or overcurrent.
Accordingly, the present invention provides a control system and a method for controlling the controller from going beyond a predefined threshold current and temperature values. The threshold current or the current limiting feature is wherein maximum current is drawn to meet the high torque requirement at minimum speed. The frequent drawing of excessive current will cause an increase in heat sink temperature. It is therefore necessary to ensure that heat sink temperature does not go beyond specified limit for reliable operation of power circuit which comprises of MOSFET's.
In one aspect of the present invention the control system continues to operate in current limit for three minutes. After three minutes, the control system gives ON/OFF signal to the motor for 30 seconds. At the same time the driver is indicated by a dashboard indication that the motor has been overloaded. This further cautions the driver to bring the vehicle at the side of the road. After 30 seconds the motor comes to a stop. Now the current in motor comes back to a value at

when the motor operates normally. This may take two minutes and after this the control system again starts the motor.
The frequent repetition of above operation may result in rise of heat sink temperature. If the heat sink temperature reaches about 105°C, the ON/OFF cycle will start again for 30 seconds. This again cautions the driver to bring the vehicle to road side. The motor stops after lapse of 30 seconds. Once the temperature reaches about 80°C which may be after several minutes, the control system again starts the motor.
Figure 1 illustrates a schematic diagram of a control system of BLDC motor according to an aspect of the present invention.
In one aspect, the BLDC motor control system comprises a microcontroller (102) connected to a - BLDC motor (104). The microcontroller (102) receives inputs from a controller input (106). In one aspect, the microcontroller (102) receives inputs from various switches and sensors such as key-on (108), accelerator (110), brake (112) and temperature sensor (114).The microcontroller (102) is connected to a MOSFET bridge circuit (116) through a discrete MOSFET driver (118) to control the flow of current in the motor windings. The motor windings are also connected to the MOSFET bridge circuit (116). Power supply terminal of the MOSFET bridge circuit (116) and the microcontroller (102) is connected to a +48 V battery (120). The output of the position sensor (122) i.e. Hall sensor is connected to the microcontroller (102) to provide the feedback of the rotor's position to the microcontroller (102), The microcontroller (102) is further configured with one or more timers.
The microcontroller (102) senses the overload condition and provides a stop signal to the BLDC motor (104). The current passing through the motor winding is sensed by a current sensor (124) such as shunt resistor and is then fed to the microcontroller (102). As there is a danger of the motor windings getting damaged due to overload or overcurrent. the current sensed by the current sensor (124) is regularly polled by the microcontroller (102). If a high current flows for a specified time period (such as for 3 minutes or more), the microcontroller (102) turns off the

power supply to the windings to the motor by switching off the MOSFETS in the MOSFET bridge circuit (116).
Figure 2 illustrates a flow chart to indicate a set of instructions embedded in microcontroller for overload protection according to an aspect of the present invention.
When the vehicle is started, the control system gets energized. Once the control system is energized, the microcontroller (102) is set to primary defined values (step 202). After setting the microcontroller (102) to primary defined values, the control system will check whether the instant temperature of the controller is more than or equal to the maximum predetermined temperature of the controller (step 204). In one aspect, the maximum predetermined temperature is set to 105°C. If the instant temperature of the controller is-more than or equal to the maximum predetermined temperature, then the controller will be set to secondary defined values (step 206). After setting the microcontroller (102) to secondary defined values, the microcontroller (102) gives an ON/OFF signal to the motor and the indicator in the dashboard of the vehicle starts to blink for a predetermined interval of time set by a second timer (step. 208). In one aspect, the second timer is set for 30 seconds. This is an indication to the rider, to bring the vehicle at the side of the road.
In step 204, if the instant temperature of the controller is less than the maximum predetermined temperature, a timer will start a predetermined interval of time set by a first timer (step 210). In one aspect, the first timer is set to 3 minutes. Once the first timer is started, the microcontroller (102) will check whether the instant current drawn by the motor (104) is smaller than a predetermined current limit (step 212). If the instant current drawn by the motor (104) is less than the predetermined current limit, then all the timers will be reset (step 214).
In step 212, if the instant current drawn by the motor (104) is greater than a predetermined current limit for predetermined interval of time set by the first timer, then the microcontroller (102) gives an ON/OFF signal to the motor (104). Also, the microcontroller (102) sends a signal to the indicator on the dashboard and the indicator will start blinking for the predetermined

interval ot time set by second timer (step 208). This is an indication to the rider to bring the vehicle to side of the road.
Meanwhile, when first timer is counting (step 216), the microcontroller (102) will keep checking whether the temperature of the controller becomes more than or equal to the maximum predetermined temperature of the controller (step 218). While the first timer is counting, if the temperature of the controller is found to be more than or equal to the maximum predetermined temperature of the controller, then the microcontroller (102) will be set to secondary defined values (step 206).At this point, the microcontroller (102) gives an ON/OFF signal to the motor (104). Also, the indicator in the dashboard of the vehicle starts to blink for a predetermined interval of time set by the second timer (step 208). This is an indication to the rider, to bring the vehicle at the side of the road.
After the predetermined interval of time set by the second timer expires, if microcontroller is set to secondary defined values (step 220), a timer will start for a predetermined interval of time set by a third timer (step 222). Further, the motor (104) will come to a stop for the predetermined interval of time set by the third timer (step 224). In one aspect, the third timer is set to 2 minutes. The microcontroller (102) will keep checking whether the time set by the third timer has expired (step 226). Once the time set by the third timer expires, the microcontroller will again start the motor (step 228).
At step 208, when the predetermined interval of time set by second timer expires, the motor (104) will come to a stop (step 230). Now the microcontroller (102) will keep checking that the temperature of the controller is below the minimum predetermined temperature of the controller (step 226). In one aspect, the minimum predetermined temperature of the controller is set to 80°C. Once the temperature of heat sink is below the minimum predetermined temperature of the controller, the control system will again start the motor (step 228). Once the motor is started, all the timers will be stopped and reset (step 214).
Figure 3 illustrates a voltage and current waveform of 3-phase BLDC motor according to an aspect of the present invention.

Aproxximately, the back EMF induced per phase of the motor winding is constant for 120 °, before and after which the back EMF changes linearly with rotor angle. In order to get constant output power and consequently constant output torque, current is driven through a motor winding during the flat portion of the its back EMF waveform. At a time, only two switches are turned on, one in a high side and the other in a low side. Thus for a star connected motor winding, two phase windings are connected in series across the DC bus, while the third winding is open.
The input switches as shown in figure 1 are switched such that each phase carries current only during the 120 ° electrical degrees when the back EMF is constant. Thus, there is a commutation event between phases every 60 ° electrical, as seen from figure 3. Effectively, it means that there is a current transition every 60 °. Appropriate commutation therefore requires knowledge of the rotor position, which can be directly detected using position sensors (hall, -sensors). In any case, the phase current is essentially constant for the 120° conduction "period. Hence, the switch current carries current for 1/3 of one electrical rotation and the current is constant for a constant load.
Figure 4 illustrates a graph showing three minute overcurrent protection and over temperature protection according to an aspect of the present invention.
As shown, in cycle 1, the motor (104) starts running within the maximum current limit at instant temperature of 45°C. The motor (104) keeps running for a period of 3 minutes and 1 second. Once the 3minute 1 second duration of first timer is about to complete, the indicator on the dashboard of the vehicle starts to blink and microcontroller (102) sends an ON/OFF signal to motor for a period of 31 seconds. Now, the instant motor is stopped for duration of 1 minute 59second, temperature reaches only 73.4°C. The motor is started again when this third timer duration completes.
In cycle 2 of the graph, the motor (104) starts running at an instant temperature of 62°C. The motor (104) keeps running for a period of 3 minutes. Once the instant temperature of the microcontroller (102) controlling the motor (104) reaches 102°C, the indicator on the dashboard of the vehicle starts to blink. Now, the instant temperature reaches to 103.2°C, microcontroller

sign motor for ON/OFF for 30 seconds duration and the motor (104) is stopped for a period of 3 minutes and 52 seconds. The motor (104) is again started when the instant temperature of the controJJer reaches 78.2°C.
In cycle 3 of the graph, the motor (104) starts running at an instant temperature of 78.2 °C. The
motor (104) keeps running for a period of 2 minutes 17 seconds. Once the instant temperature of
the controller controlling the motor (104) reaches 102.5°C, the indicator on the dashboard of the
vehicle starts to blink. Now, the instant temperature reaches to 103.5°C, microcontroller signals
motor for ON/OFF for 31 seconds duration and the motor (104) is stopped for a period of 5
minutes and 15 seconds. The motor (104) is again started when the instant temperature of the
controller reaches 80°CJ. *
In cycle 4 of the graph, the motor (104) starts running at an instant temperature of 80°C. The motor (104) keeps running for a period of 2 minutes. Once the instant temperature of the microcontroller (102) controlling the motor (104) reaches 103.2°C, the indicator on the dashboard of the vehicle starts to blink for a period of 29 seconds. Now, the instant temperature reaches to 95.4°C, microcontroller signals motor for ON/OFF for 31 seconds duration and the motor (104) is stopped for a period of 5 minutes and 19 seconds- The motor (104) is again started when the instant temperature of the controller reaches 79.2°C.
In cycle 5 of the graph, the motor (104) starts running at an instant temperature of 78.2°C. The motor (104) keeps running for a period of 2 minutes 7 seconds- Once the instant temperature of the microcontroller (102) controlling the motor (104) reaches 103.4°C, the indicator on the dashboard of the vehicle starts to blink. Now, the instant temperature reaches to 104.5°C, microcontroller signals motor for ON/OFF^for 30 seconds duration and the motor (104) is stopped for a period of 5 minutes and 40 seconds. The motor (5 04) is again started when the instant temperature of the microcontroller (102) reaches 79.5°C.
The advantages of the disclosed invention are thus attained in afi economical, practical, and facile manner. While preferred aspects and example configurations have been shown and described, it is to be understood that various further modifications and additional configurations will be

apperment to those skilled in the art. It is intended that the specific aspects/ embodiments and configurations herein disclosed are illustrative of the preferred and best modes for practicing the invention, and should not be interpreted as limitations on the scope of the invention.
ADVANTAGES OF THE PRESENT INVENTION
The present invention has the following advantages:
1. The control system based thermal protection system will enhance reliability of controllers for
electric vehicles.
2. Overload condition of vehicles are known to driver by way of dashboard indication and
ON/OFF operation of the motor.
3. Controller will not fail under severe gradient conditions. '*
4. System provides optimum utilization of power circuit.
5. Restricted current limit feature avoids heavy drainage of battery.

We Claim.
1. A control system for protecting overload conditions in controller of electric vehicles having a brushless direct current (DC) motor (104), said control system comprising: a microcontroller (102);
a temperature sensor (114) for measuring an instant temperature of the controller; and a current sensor (124) for measuring an instant current drawn by the motor (104); wherein said microcontroller comprises:
a comparator circuit configured to issue a first signal based on comparison of the
instant temperature of the controller with a maximum/minimum predetermined temperature of
the controller;
an overcurrent detection circuit configured to issue a second signal based on comparison of the instant current drawn by the motor with a predetermined current limit of the controller; and
a cut-off circuit for restricting supply of current to the motor (104) based upon issuance of said first and second signal.
2. The control system as claimed in claim 1, wherein the comparator circuit issues the first signal when the instant temperature is determined to be greater than the maximum predetermined temperature.
3. The control system as claimed in claim 1, wherein the overcurrent detection circuit issues the second signal when the instant current is determined to be greater than a predetermined current limit.
4. The control system as claimed in claim 1. wherein the control system comprises one or more timers.
5. The control system as claimed in claim 4, wherein the comparator circuit and overcurrent circuit are configured to repeat comparison operations for a predefined interval of time set by a first timer.

6. Tele control system as claimed in claim 4, wherein the microcontroller (102) is configured with an output signal to alternatively start and stop the motor and produce an ON/OFF signal for a predefined interval of time set by a second timer.
7. The control system as claimed in claim 4, wherein the supply of current to the motor (104) is restricted for a predefined interval of time set by a third timer.
8. The control system as claimed in any of the preceding claims, wherein the microcontroller (102) is configured with an output signal to restart the motor (104) and stop and reset the at least one timer after expiry of the predefined interval of time set by the third timer.
9. The control system as claimed in any of the preceding claims, wherein the microcontroller (102) is further configured to stop and reset the at least one time*r when said first current is determined to be lesser than the predetermined current limit.
10. The control system as claimed in claim 1, wherein the microcontroller (102) is operatively connected to the brushless DC motor (104) through a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) bridge circuit (116) enabled by a MOSFET driver (118).
11. The control system as claimed in claim 1, wherein the microcontroller (102) is operatively connected to the temperature sensor (114) and the current sensor (124).
12. A method for protecting overload conditions in controller of electric vehicles having a brushless DC motor(104), said method comprising the steps of:
measuring an instant temperature of the controller by a temperature sensor (114); measuring an instant current drawn by the motor (104) by a current sensor (124);
comparing the instant temperature of the controller with a maximum/minimum predetermined temperature of the controller and issuing a first signal based on said comparison;
comparing the instant current drawn by the motor (104) with a predetermined current limit of the controller and issuing a second signal based on said comparison;

starting and stopping the motor alternatively and producing an ON/OFF signal based upon issuance of said first and second signal; and
restricting supply of current to said motor (104) based upon issuance of said first and second signal.
13. The method as claimed in claim 12, wherein the first signal is issued when the instant temperature is determined to be greater than the maximum predetermined temperature.
14. The method as claimed in claim 12, wherein the second signal is issued when the instant current is determined to be greater than the predetermined current limit.
J — . ■: ■
15. The method as claimed in claim 12, wherein comparing the instant temperature/current with the
predetermined temperature/current limit for a predefined interval of time set by a first timer.
16. The method as claimed in claim 12, wherein starting and stopping the motor alternatively and
producing an ON/OFF signal for a predefined interval of time set by a second timer.
. 17. The method as claimed in claim 12, wherein restricting supply of current to the motor upon determination of the instant temperature of the controller to be greater than the maximum predetermined temperature.
18. The method as claimed in claim 12, wherein restricting supply of current to the motor upon determination of the instant current drawn by the motor (104) to be greater than the predetermined current limit and the instant temperature of the controller to be greater than the maximum predetermined temperature.
19. The method as claimed in any of claims 17 and 18, wherein restarting the motor upon determination of the instant temperature of the controller to be less than the minimum predetermined temperature.

20. Tnlwrfiethod as claimed in claim 12, wherein restricting supply of current to the motor for a predefined interval of time set by a third timer upon determination the instant temperature of the controller to be less than the maximum predetermined temperature and instant current drawn by the motor (104) to be greater than the predetermined current limit and restarting the motor thereafter.
21. The method as claimed in claim 12, wherein setting the predetermined temperature within the range of 70-120°C.
22. The method as claimed in claim 12, wherein setting the predetermined current limit within the rangecf30A±lA.