Claims:1. A system (10) for automatic load current detection, said system comprising:
a motor driver module (11) configured to control operation of a motor;
a controller unit (12) communicably coupled to the motor driver module (11) and adapted to control the operation of the motor;
a voltage sensing module (13) to monitor supply condition of line voltage, when the motor driver module (11) receives a signal to start the motor from the controller unit (12);
a timer setting module (14) communicably coupled to the controller unit (12) to receive a timer signal from therein; and
a data acquisition module (15) communicably coupled to the controller unit (12) and adapted to:
record (S21) first three cycles of input power supply as inrush current characteristic of the motor;
record (S22) the voltage and current relation during inrush current characteristic of the motor;
record (S23) both motor load current and line voltage for next five cycles of the input power supply;
determine (S24) if Root Mean Square (RMS) values of next five cycles of the input power supply are consistent with the line voltage;
record (S25) full load current of the motor when the RMS values of the next five cycles are consistent with the line voltage; and
set (S26) a dry run protection threshold based on the recorded load current of the motor.

2. The system as claimed in claim 1, wherein if the line supply is healthy, the voltage sensing module (12) monitors current along with the line voltage.

3. The system as claimed in claim 1, wherein the controller unit (12) is a GSM (Global System for Mobile communication) controller unit and said unit comprises a GSM device (17) and a SIM (Subscriber Identification Module) card (18).

4. The system as claimed in claim 1, wherein the motor load current begins to settle down after the first three cycles of input power supply.

5. The system as claimed in claim 1, further comprising a fault indication module (16) to display a fault indication.

6. The system as claimed in claim 5, wherein the indication module (16) is preferably a LED (Light Emitting Diode) screen.

7. A method for automatic load current detection, said method comprising the steps of:
recording (S21) first three cycles of input power supply as inrush current characteristic of a motor;
recording (S22) voltage and current relation during inrush current characteristic of the motor;
recording (S23) both motor load current and line voltage for next five cycles of the input power supply;
determining (S24) if Root Mean Square (RMS) values of next five cycles of the input power supply are consistent with the line voltage;
recording (S25) full load current of the motor when the RMS values of the next five cycles are consistent with the line voltage; and
setting (S26) a dry run protection threshold based on the recorded load current of the motor.

8. The method as claimed in claim 7, wherein the motor load current begins to settle down after the first three cycles of input power supply.
, Description:FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to automatic load current detection and more particularly, pertains to a system and a method for automatic load current detection.

BACKGROUND OF INVENTION

[002] Farmers irrigate their farms using water from wells and underground water resources with the aid of water pumps. Conventional water pumps were traditionally operated manually, however, with passage of time; automatic starters are now available in market. The purpose of these is to aid the farmer to turn on or turn off the motor remotely, from anywhere. This does away with the need for the farmer to be physically present to turn off or turn on the motor.

[003] Mobile phones are an extremely fast and ever-growing network of physical systems that allow communication between one or more objects. Presently, a variety of automatic water pump starter control systems or remote pump operator systems using mobile phones to control their operations are available in market. With the advent of such systems, the farmer need not go to the farm to water their field. They can operate the motor from anywhere conveniently. Further, no cabling or hardware connections are required. These systems employ wireless communication.

[004] In particular, GSM communication is used to switch ON/OFF the pump by SMS/Missed call/IVRS and android App. The GSM modem performs the task of receiving the message, call from the mobile and sending the messages to the mobile from the controlling unit. To the motor, GSM modem with the controlling unit will be fixed. When the farmer wishes to water their field, i.e., switch on the motor, they send a predefined message to the modem from their mobile. The GSM modem receives this message and intimates the same to the microcontroller. The same process is repeated for turning the water pump off as well.

[005] For some state of the art technology, reference is made to IN 201721043506 wherein a smart automatic water pump starter control system using mobile phones to control the pump operation automatically is disclosed. They also offer dry run protection. However, this system does not detect full load current automatically without manual intervention.

[006] Reference is also made to IN 201641041444 wherein automatic flowrate measurement and control of water flow using telemetry is disclosed. It is designed to acquire the water meter reading automatically, transfer and receive data from central unit through a GSM module. Hall sensor is being used to obtain magnetic pulse. However, this system also does not detect full load current automatically without manual intervention.

[007] Reference is further made to IN 201717016961 wherein an electric current estimating device is disclosed. A power conversion circuit and a current estimating device are applied to a system comprising a rotating electrical machine that performs direct-current power supply and the power transmission by energization operation to the power conversion circuit. However, this document deals with direct current and theoretical calculation has been opted to estimate the current.

[008] In the present scenario, motor full load current is entered manually by users. In particular, the user is supposed to press “Load Set” push button available on unit to set the load current. Whenever this load set button is pressed, units record the current available at that moment as a “full load motor current”.

[009] A primary drawback associated with this technique is that whenever the “Load Set” button is pressed, irrespective of the health of the electrical condition, load current gets recorded by the unit. Since this method involves manual intervention, the unit can record current in presence of fault too. This results in erroneous detection of full load current and eventually no effective dry run protection or nuisance tripping due to wrong settings.

[0010] Another drawback associated with this technique is that it does not concern itself with the inrush current characteristic of the motor. During this inrush current, if a user set the load current, a very high load current (almost 6 times of actual load current) will be recorded there resulting in ineffective dry run protection.

[0011] Moreover, to prevent pump from dry run, pick up threshold setting needs to be set by user. If water in bore well/tank goes below this pick up threshold, dry run fault is detected. This setting is percentage multiple of full load current of motor such as 50% of IFL (motor full load current). For accurate fault detection, motor full load current has to be precise. In present scenario, this motor full load current parameter is set manually by customer. Due to any reason, if it is not set correctly, the protection of dry run will not be effective and it may lead burning of water pump.

[0012] Accordingly, there is a need to overcome the drawbacks associated with the conventional automatic water pump starter systems. In particular, to there is a need for automatic and accurate detection motor load current as per available voltage.

[0013] The above-described need for a system and a method for automatic load current detection are merely intended to provide an overview of some of the shortcomings of conventional systems / mechanism / techniques, and are not intended to be exhaustive. Other problems/ shortcomings with conventional systems/ mechanism /techniques and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.

SUMMARY OF THE INVENTION

[0014] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0015] An object of the present invention is to alleviate the drawbacks associated with conventional automatic water pump starter control systems.

[0016] Another object of the present invention is to provide a system and a method for automatic load current detection.

[0017] Yet another object of the present invention is to provide automatic full load current detection by a data acquisition system in GSM based controller for a three phase motor starter.

[0018] According to a first aspect of the present invention, there is provided a system for automatic load current detection. The system comprising a motor driver module, a controller unit, a voltage sensing module, a timer setting module and a data acquisition module. The motor driver module is configured to control operation of a motor. The controller unit is communicably coupled to the motor driver module and adapted to control the operation of the motor. The voltage sensing module monitors supply condition of line voltage, when the motor driver module receives a signal to start the motor from the controller unit. The timer setting module is communicably coupled to the controller unit to receive a timer signal from therein. The data acquisition module is communicably coupled to the controller unit and adapted to: record first three cycles of input power supply as inrush current characteristic of the motor; record the voltage and current relation during inrush current characteristic of the motor; record both motor load current and line voltage for next five cycles of the input power supply; determine if Root Mean Square (RMS) values of next five cycles of the input power supply are consistent with the line voltage; record full load current of the motor when the RMS values of the next five cycles are consistent with the line voltage; and set a dry run protection threshold based on the recorded load current of the motor.

[0019] In one possible implementation of the system for automatic load current detection according to the first aspect, if the line supply is healthy, the voltage sensing module monitors current along with the line voltage.

[0020] In another possible implementation of the system for automatic load current detection according to the first aspect, the controller unit is a GSM (Global System for Mobile communication) controller unit and said unit comprises a GSM device and a SIM (Subscriber Identification Module) card.

[0021] In yet another possible implementation of the system for automatic load current detection according to the first aspect, the motor load current begins to settle down after the first three cycles of input power supply.

[0022] In yet another possible implementation of the system for automatic load current detection according to the first aspect, a fault indication module displays the fault indication preferably on a LED (Light Emitting Diode) screen.

[0023] According to a second aspect of the present invention, there is provided a method for automatic load current detection. The method comprising the steps of recording first three cycles of input power supply as inrush current characteristic of a motor; recording voltage and current relation during inrush current characteristic of the motor; recording both motor load current and line voltage for next five cycles of the input power supply; determining if Root Mean Square (RMS) values of next five cycles of the input power supply are consistent with the line voltage; recording full load current of the motor when the RMS values of the next five cycles are consistent with the line voltage; and setting a dry run protection threshold based on the recorded load current of the motor.

[0024] In one possible implementation of the method for automatic load current detection according to the second aspect, the motor load current begins to settle down after the first three cycles of input power supply.

[0025] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0026] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0027] Figure 1 illustrates the block diagram of the system for automatic load current detection, in accordance with a first embodiment of the present invention.

[0028] Figure 2 illustrates flow-chart of the method for automatic load current detection, in accordance with a second embodiment of the present invention.

[0029] Figure 3 illustrates the current-time diagram depicting inrush characteristics, in accordance with an aspect of the present invention.

[0030] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0031] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0032] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0033] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0034] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0035] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0036] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0037] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0038] The present invention lies in providing a system and a method for automatic load current detection.

[0039] The drawbacks associated with the existing systems is that whenever the “Load Set” button is pressed, irrespective of the health of the electrical condition, load current gets recorded by the unit. Since this method involves manual intervention, the unit can record current in presence of fault too. This results in erroneous detection of full load current and eventually no effective dry run protection or nuisance tripping due to wrong settings. Further, these systems do not consider the inrush current characteristic of the motor thereby resulting in ineffective dry run protection.

[0040] To overcome said drawbacks of conventional systems, the exemplary embodiments of present invention disclose automatic load current detection for dry run protection setting by employing a data acquisition system with the GSM controller of a three-phase motor.

[0041] The first embodiment of the present invention, as illustrated in Figure 1, discloses a system for automatic load current detection. The system comprising a motor driver module (11), a controller unit (12), a voltage sensing module (13), a timer setting module (14), a data acquisition module (15) and a fault indication module (16).

[0042] The motor driver module (11) is configured to control operation of a motor. The controller unit (12) is communicably coupled to the motor driver module (11) and adapted to control the operation of the motor. The voltage sensing module (13) is inbuilt and monitors supply condition of line voltage, when the motor driver module (11) receives a signal to start the motor from the controller unit (12). The timer setting module (14) is communicably coupled to the controller unit (12) to receive a timer signal from therein. The data acquisition module (15) is communicably coupled to the controller unit (12). The fault indication module (16) displays the fault indication and is preferably a LED (Light Emitting Diode) screen.

[0043] The data acquisition module (15) is adapted to perform the following steps, as illustrated in Figure 2. In particular, the data acquisition module (15) performs the following functions:
records (S21) first three cycles of input power supply as inrush current characteristic of the motor;
records (S22) the voltage and current relation during inrush current characteristic of the motor;
records (S23) both motor load current and line voltage for next five cycles of the input power supply;
determines (S24) if Root Mean Square (RMS) values of next five cycles of the input power supply are consistent with the line voltage;
records (S25) full load current of the motor when the RMS values of the next five cycles are consistent with the line voltage; and
sets (S26) a dry run protection threshold based on the recorded load current of the motor.

[0044] Significantly, if the line supply is healthy, the voltage sensing module (12) monitors current along with the line voltage. The controller unit (12) is a GSM (Global System for Mobile communication) controller unit and said unit comprises a GSM device (17) and a SIM (Subscriber Identification Module) card (18). The motor load current begins to settle down after the first three cycles of input power supply. A fault indication is generated whenever a fault is detected. A fault is detected when the voltage is not healthy, i.e., not within the permissible limits. For example, faults such as over voltage, under voltage, phase reversal; single phasing, dry run, etc. are detected.

[0045] Notably, inrush current is the maximum current drawn by an electrical circuit at the time it’s turned ON. It appears for the few cycles of input waveform. The value of the inrush current is much higher than the steady-state current of the circuit and this high current can damage the device or trigger the circuit breaker. Inrush current generally appears in all the devices where magnetic core is present like transformers, industrial motors etc.

[0046] Thus, the present invention introduces a built-in data acquisition for automatic full load current detection to ensure that full load motor current is not recorded during a fault or inrush current of motor. Whenever “Pump ON” command is issued from unit, it starts monitoring line voltage to ensure healthy supply condition. If supply is healthy, it starts monitoring current along with line voltage. First three cycles of supply are recorded as inrush current characteristic of motor as illustrated in Figure 3. Both voltage and current relation during inrush characteristic zones are recorded. After three power cycles, when motor load current starts settling down, it is further observed for next five cycles along with line voltage. If RMS value of five cycles is consistent at healthy line voltage, this has been recorded as motor full load current. Based on this recorded load current, dry run protection threshold is set. No manual intervention is requited to set motor load current. Hence it is very precise and error free.

[0047] The present invention finds its application in farms to remotely control irrigation of farmlands by farmers.

[0048] Some of the non-limiting advantages of the present invention are mentioned hereinbelow:
a) It provides automatic detection of full load motor current in GSM controllers for three phase motor;
b) It provides an inbuilt data acquisition system to monitor and record line voltage and motor load current in GSM controller; and
c) It provides an error free full load motor current setting for dry run protection of the automated system.

[0049] Although a system and a method for automatic load current detection has been described in language specific to structural features and/or methods as indicated, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or components or devices or methods described therein. Rather, the specific features are disclosed as examples of implementations for automatic load current detection for dry run protection setting by employing a data acquisition system with the GSM controller of a three-phase motor.