, Description:Electronic over-current circuit breaker for protection against over-current faults
FIELD OF INVENTION

[001] The present invention relates to the field of circuit breaker. The present invention more particularly relates to electronic over-current circuit breaker for protection against over-current faults. The invention is pertinent to din mountable electronic over-current breaker so as to restrict load up to the current value pre-set by user or manufacturer, for the purpose of protection against over-current faults.

BACKGROUND/PRIOR ART

[002] Currently, mechanical circuit-breakers are employed for protection from overload faults. One such example is the miniature circuit breaker or MCBs. However, the problem with mechanical circuit-breakers like MCB is that they have pre-defined factory-set rating. These are provided in certain limited typical current rating values such as 1A, 2A, 4A, 6A, 10A, 16A, 25A, 32A, 40A, 50A, 63A etc. These ratings are limited mainly because manufacturing too many current rating MCBs does not make a good business sense and also tends to increase the investment for a producer exponentially. Moreover it is much difficult to make fine distinctions in rating in mechanical type of circuit breakers. In case, a load needs finer protection in between current ratings, user has to compromise due to unavailability of desired rating of MCB.

[003] Another problem is that there is no provision for displaying the value of parameters such as current, voltage, frequency, power, energy etc. of the power supply on the device. Hence verification of the device functionality and circuit parameters is not possible without additional measuring device (e.g. clamp-meter to measure current) which may not be readily accessible.

[004] Further users do not receive any pre-trip indication warning that circuit is about to disconnect. Very often a sudden interruption of important processes, when the circuit breaker trips in case of fault, causes a loss of work and data, which could have been avoided had the user got an intimation as soon as certain threshold was crossed, as he could have taken corrective/maintenance actions.

[005] Certain electronic circuit breakers are also known to have been provided in the art, which can be discussed hereinunder.

[006] Indian application number 5904/DELNP/2015 discloses a programmable circuit breaker including an input unit, a sensor and a trip mechanism. The input unit permits user input and/or adjustment of predetermined load parameters.

[007] The sensor senses actual values of a load. A microcontroller receives and processes the values and operates/trips the circuit breaker when the sensed values exceed predetermined load parameters. The invention seeks to provide a power distribution system and method, in which the predetermined parameters maybe preset and thereafter adjusted by a user.

[008] The above discloses an intricate method of current sensing by implementing hall-effect current sensors. Further, said circuit breaker does not support a method of local current rating adjustment on the body of the circuit breaker rather adopts a sophisticated method.

[009] Publication No. CN201478783 (U) relates to an electronic over-current protector, comprising: a high-frequency current detecting and buffering circuit that outputs the buffered high-frequency current signal. A dynamic over-current protection threshold adjusting circuit is connected with the high-frequency current detecting and buffering circuit. A transient detecting circuit is provided in connection with the high-frequency current detecting and buffering circuit together with a comparator in connection with the dynamic over-current protection threshold adjusting circuit and the transient detecting circuit. A locking contravariant pulse output and over-current indicator is connected with the comparator, a tripping controller is connected with the locking contravariant pulse output and over-current indicator, and the output end is connected with a power brake of the protected device.

[0010] It has provision for an over current protection circuit for high frequency power source. This device is neither provided with the feature of pre-trip fault current indication nor over-current protection for current ratings which can be selected and set by user.

[0011] Publication No. CN202855658 (U) is directed to an emergency protective circuit device responding to over current, particularly, relates to an adjustable electronic current-limiting circuit breaker, which includes a current-limiting circuit breaker body as well as a micro controller and an electronic time delay device which are connected with the current-limiting circuit breaker body. In particular, the micro controller and the electronic time delay device are integrated in the current-limiting circuit breaker body; and the front surface of the current-limiting circuit breaker body is provided with an operating handle, a test button and a rated current regulator.

[0012] It is not having provision for pre-trip indication, nor does it have display facility of different real-time electrical parameters. There is provided a test button together with current regulator having a nominal 80A, 100A, 125A and 160A four stalls.

[0013] Publication No. CN2323501 (Y) provides a multifunctional adjustable electronic circuit breaker, which is a device of security protection of a motor carried out by an electric power system in the electric technical field. Three load lines are penetrated through current transformers LH1, LH2 and LH3. Phase loss signals and over current fault signals are taken samples and input into comparators IC2 and IC3. The switching-in and the switching-off of triodes T3 and T4 are used for controlling the switching of a relay J through IC4 or a non gate circuit. The switching of a breaker switch is driven to actualize protection for lines. RW1 is used for establishing a normal current magnitude, wherein RW2 is 7 times the size of the normal current magnitude.LED is used for running indication. A power supply voltage, a setting current and a running load current are monitored through a transfer switch. The LCD is used for measurement display.

[0014] The above patent uses a different circuitry of electronic circuit breaker, especially for protection of a motor. Here, the rated current setting is adjusted according to load current. Further, there is no provision of pre-trip fault current indicator nor inverse time current characteristics for tripping.

[0015] Publication No. 20120293902 discloses an over-current protection circuit for preventing a function module from over-current. The over-current protection circuit includes a path switch, a current detection circuit, a conductor switch, a first control module, and a second control module. The current detection circuit and the path switch form a loop with the input port and the function module. The current detection circuit detects a value of a current of the loop, and produces a first control signal when detecting the current of the loop is equal to or greater than a predetermined current value. The first control module turns off the conductor switch when receiving the first control signal. The second control module turns off the path switch when the conductor switch is turned off, thereby cutting off the loop.

[0016] The aforesaid patent introduces a different electronic circuit for over-current protection with no feature of pre-trip fault current indication. Further, there is no over-current protection for current ratings that are adjustable by user.

[0017] Earlier modular devices used for circuit-breaking (MCBs) are mechanical in nature, which work to break the circuit for defined current ratings.

[0018] Being mechanical in nature, the speed of response is slow. Moreover their accuracy and reliability is also quite low.
[0019] Due to unavailability of adjustable current rating feature in modular mechanical breakers, if load value changes, new device is required. It is difficult to manufacture, store or transport so many SKUs of finely different ratings and likewise difficult for the user too. Thus, there is no modular device which has variable current rating option on its body.

[0020] Thus, in view of the above, there is a requirement to devise a circuit breaker which can obviate shortcomings of the afore discussed prior arts and serve the purpose efficiently by being operated by an electronic method for sensing fault and disconnecting the circuit which in turn contributes to the fast response and adds to the accuracy and reliability of the product.

OBJECTS OF THE INVENTION

[0021] The principal objective of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which restricts load up to the current value pre-set by user or manufacturer.

[0022] Another object of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which is reliable, accurate and cost effective.

[0023] Yet another object of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which is flexible and ensures a quick response.
[0024] Still another object of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which displays various parameters on the breaker.

[0025] Yet another object of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which gives pre-trip fault warning indication to the user.

[0026] Another object of the present invention is to provide electronic over-current circuit breaker for protection against over-current faults which is compact, modular and din-rail mountable; suitable for use in distribution boards.

SUMMARY OF THE INVENTION

[0027] According to this invention, there is provided electronic over-current circuit breaker for protection against over-current faults comprising a sensing switch for adjusting the current rating, a controller to sense the value of current pre-set by user and trip the breaker according to inverse time characteristics, a pre-trip indicator, a visual indicator to indicate circuit parameters and a toggle switch to switch on/off the breaker.

[0028] Thus, the present invention provides an electronic over-current breaker which restricts load up to the current value pre-set by user or manufacturer, for the purpose of protection against over-current faults. There is provision of an electronic method for sensing fault and disconnecting the circuit which in turn contributes to the fast response and adds to the accuracy and reliability of the breaker. Also a display is installed which informs user of the pre-set value of current, the present value of current flowing in circuit and also other parameters such as voltage, frequency, power, energy etc. It also gives a pre-trip indication as soon as the current crosses pre-defined threshold, thus warning the user that circuit is about to trip and some measures must be taken such as to save the on-going work etc.

[0029] Further, it is modular and compact with the provision of din-rail mounting. The invention acts as a limiting device for that particular current till a new input is fed in the memory.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0030] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:

Figure 1 shows: Electronic over-current circuit breaker for protection against over-current faults according to the present invention.
Figure 2 shows: Block diagram of internal circuit in accordance with the present invention.

DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0031] The present invention makes a disclosure regarding a technology pertinent to an electronic over-current breaker to sense fault and disconnect the circuit when current drawn is beyond the finely adjustable preset threshold. Further prior to tripping, user receives a warning so that any corrective action can be taken if required.
[0032] In conjunction with the above, the invention provides an electronic method for sensing fault as well as the breaking of contacts for adjustable current rating, following inverse time current characteristics of circuit-breakers for overload protection and pre-trip fault indication.

[0033] Now, reference may be made to fig. 1 indicating features of breaker of invention, which includes a sensing switch such as tact switch (1) on the front for adjusting the current rating. A 7-segment display unit (2) is provided which shows the value of the limiting current set by the user, the real-time current flowing in circuit as well as other parameters such as voltage, frequency, power, energy etc. Pre-trip indication is provided by means of LED (3) which glows when the current reaches a certain threshold value and the circuit is about to trip. There is provision of a toggle switch (4) on front to power on/off the device. Incoming and outgoing line neutral connections (I and O) can be made available at top and bottom terminals. The rear face of device has upper and lower recesses for engaging with the flanges of din-rail, and a din-clip is provided at bottom to hold the device on din-rail and also to remove it from din-rail. Further the inventive device is compact, modular and can be installed in distribution boards with ease or implemented for localized applications.

[0034] Various units and their function is described hereinunder with reference to the block diagram as illustrated in Figure 2. The device can be powered on by toggle switch (4) placed on front. Power supply unit (1') is provided which makes appropriate voltage and current supply from the incoming input line (2').This is used to operate the controller unit (3'). The user can adjust current rating by means of tact switch (1). Whenever the switch is pressed, the controller gets a signal and increases the current rating by say 0.2A. In case, the switch is kept pressed for a long time, the rating increases at a faster rate.

[0035] The incoming phase line passes through the relay switch (4') and the current-transformer (5'). The controller senses the real-time current by means of voltage drop across a resistor (not shown).

[0036] The controller also gives pre-trip warning signal to LED indicator (3) or other visual indication on display (2) of device. For example pre-trip warning threshold may be set in controller (3') as equal to rated current or some fractions of rated current. The controller also senses or determines various circuit parameters such as current, pre-set rated current, voltage, frequency, power, energy etc. and gives visual indication on display (2) of device.

[0037] The user can consider pre-trip indication as a warning that he should save the data or take other preventive/ corrective action as required such that the work under process is not abruptly interrupted.

[0038] The controller is designed to follow inverse time-current tripping characteristics. Here, time taken to break the circuit is inversely proportional to intensity of overload current. In this way the device can also be designed to follow overload zone curve of MCB’s tripping characteristics. In case of fault, the controller gives signal to relay to disconnect the circuit at appropriate time.

[0039] After the circuit is tripped, the controller is designed such that it again gives signal to relay to close the contacts after lapse of pre-defined time. Incase the fault persists the circuit is again disconnected. This continues for a limited number of cycles prompting the user to decrease the load. If the user limits the load, the device resumes its normal operation. If the user does not limit the load even after a number of prompts, the circuit gets permanently disconnected after a fixed number of cycles. Eventually, it is switched on only by resetting the toggle switch.

[0040] The pre-set current can be adjusted by user in small steps, such as 0.2A, hence a large variants of device rating can be made available from same breaker, which is not possible for currently available mechanical circuit breakers.

[0041] While the working is explained by means of a tact switch, other kind of sensing switches can also be provided on the body of circuit-breaker for adjusting current rating.

[0042] As the electronic over-current breaker of invention is operated by electronic working method, response time is quick and accuracy as well as reliability is better in comparison to conventional mechanical circuit breakers or MCBs.

[0043] Advantageous Features

- Modular and din-rail mountable
- Compact
- Quick and accurate operation
- Reliable
- Flexible and cost effective
- Provision of pre-trip indicator for fault warning.
- Indication of circuit parameters

[0044] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

Claims:WE CLAIM:
1.Electronic over-current circuit breaker for protection against over-current faults comprising a sensing switch for adjusting the current rating, a controller to sense the value of current pre-set by user and trip the breaker according to inverse time characteristics, a pre-trip indicator, a visual indicator to indicate circuit parameters and a toggle switch to switch on/off the breaker.

2. The electronic over-current breaker as claimed in claim 1 wherein the controller follows inverse time-current tripping characteristics such that it can be designed to follow overload zone curve of MCB characteristics.

3. The electronic over-current breaker as claimed in claim 1 or 2 wherein the visual display reflects the circuit parameters such as voltage, frequency, pre-set value of current, present value of current flowing in circuit, power, energy etc.

4. The electronic over-current breaker as claimed in any of the preceding claims wherein the incoming phase line is provided through a relay switch and current-transformer.

5. The electronic over-current breaker as claimed in any of the preceding claims wherein the breaker provides a pre-trip indication when the current crosses a pre-defined threshold which can be equal to pre-set current rating or fractions of pre-set current rating.
6. The electronic over-current breaker as claimed in any of the preceding claims wherein the controller transmits pre-trip warning signal to the visual indicator such as LED.

7. The electronic over-current breaker as claimed in any of the preceding claims wherein the pre-set value is adjustable by user in small current steps by means of the sensing switch, which triggers the controller to increase the current rating.

8. The electronic over-current breaker as claimed in any of the preceding claims wherein following circuit disconnection, the breaker again gets re-connected, which continues for a fixed number of cycles thereby prompting the user to reduce load, in which the breaker is resettable by toggle switch after fixed number of cycles.

9. The electronic over-current breaker as claimed in any of the preceding claims is associated with the advantageous features such as herein described.