DESC:TECHNICAL FIELD OF THE INVENTION

This invention relates generally to circuit breakers. More particularly the present invention relates to an improved electronic trip unit for circuit breakers. It provides for an implementation of single chip solution for Monitoring, Protection, Fault Recording, Navigation, Communication and Display Control of Electronic Trip Units used in Circuit breakers.

BACKGROUND AND THE PRIOR ART

An electronic trip unit is basically used to provide Protection and Control for circuit breaker under fault conditions. The function of protection trip unit is to cause prompt discontinuation of service in presence of a short circuit, or when it starts to operate in any abnormal manner that might cause damage or otherwise interfere with the effective operation of the rest of the system. Additionally, Navigation for system & protection settings, metering of the analog signals sensed and communication is the functionality of an advanced electronic trip unit.

In the existing trip units of Circuit breakers, the myriad functions are performed by multiple microprocessors / microcontrollers. This results in excessive power consumption which is extremely critical in case of power sensitive application like a self-powered Electronic Trip Unit of a circuit breaker. In addition to that, the hardware requirement increases which leads to space constraints. The communication between the multiple processor cores consume CPU load. The driving of LCD is done by an in-built or external LCD driver which adds cost and limits the selection of micro controller to specific parts and manufacturers. Our invention offers a standard, non-specific, single chip solution for the above mentioned functionalities. The integrated solution aims at offering a compact, power efficient and cost effective electronic trip unit.

OBJECTS OF THE INVENTION

A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to provide a single chip solution for trip unit to be used in circuit breaker.

Another object of the present invention is to provide a Single IC performing display driver function using GPIO.

Another object of the present invention is to provide a Single IC performing DSP function without separate engine.

Another object of the present invention is to provide an IC working at higher frequency yet compensating for increased current by moving into sleep mode frequently.

Another object of the present invention is to provide an IC having the flexibility of incorporating the updated functionalities in future course without calling for change in core architecture.

Yet another object of the present invention is to provide a compact, energy efficient and cost effective state of the art trip units with contemporary features.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

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.

In an aspect of the present invention, there is provided an electronic trip unit for circuit breaker(s), said unit comprising:
a signal conditioning module for providing input signal;
a select switch(s) for providing controlled setting for navigation and protection to said electronic trip unit;
a controller means comprising a converting means, and a memory;
wherein said controller means connected to signal conditioning module and said select switch(s), facilitating signal monitoring and metering, providing protection against an electrical fault with an indication and recording, and communicating to a remote location and driving an display means.

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

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Reference is first invited to Fig 1 where the block diagram of trip unit with various modules is shown.

Fig 2 shows Display driver function using general purpose input output (GPIO).

Fig 3 shows Modbus communication over universal asynchronous receiver transmitter (UART).

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 INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. 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 and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

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

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.

Accordingly, present invention provides an integrated solution that aims at offering a compact, power efficient and cost effective electronic trip unit. Selection of micro controller is most important task in order to achieve the functionality of:

(a) Signal Monitoring – Requires at least 8 channels and ADC with 12 bit resolution
(b) Protection against various electrical faults – High frequency and DSP functionality
(c) Metering – accuracy better than 1.5% requires high resolution ADC and DSP functionality
(d) Man Machine Interface (Switches and display) – High frequency and multi tasking with pipe line fetching
(e) Communication – UART function
(f) Motor Operator interface – UART & GPIO function
(g) Event recording – Internal memory management
(h) RTC – Low power wafer enable in shut down mode

All the above functions are intended to be performed by single general purpose micro controller, either 16 bit or 32 bit. Most of microcontrollers meet few of the above mentioned functions leaving others to be implemented using different micro controller or dedicated driver IC.

For example, micro controller with dedicated display driver limits the ADC Input output lines to fewer than expected or resolution to lower than expected. In this case the novelty lies in converting general purpose input output pins to perform the display driver function and getting the criteria of having display driver, either internal or external, thereby expanding the range of micro selection.

Metering and protection function requires DSP functionality which either calls for dedicated micro controller or separate DSP IC. In this case the novelty lies in multi tasking and scheduling (not within the scope of description)the work so as to effective use bandwidth of micro controller with its existing architecture to perform complex algorithm in split form and achieving better accuracy.

To perform the complex algorithm calculation and addition overhead task of LCD driving requires operation of IC at higher frequency which causes for higher current consumption. The novelty here lies in effectively performing the entire necessary task and putting the micro control in sleep mode to reduce the power consumption without compromising on functionality such as UART which is made available even in sleep mode so that no data is lost during communication with external environment.

Event recording and management generally requires external IC. But with improved algorithm, the existing flash is used as non-volatile memory for event recording. The entire above mentioned task is effectively incorporated in one micro controller with stable and effective software architecture thus giving advantage of cost with reduced hardware, saving in power with reduced hardware and flexibility in controller without dependence on specific drivers.

The purpose of the invention is to have single chip solution for trip unit to be used in circuit breaker. This requires the entire above mentioned task to be performed without having need for separate additional IC at various levels. This helps in developing the most compact, energy efficient and cost effective state of the art trip units with contemporary features. There is provided an algorithm to address the above mentioned issue.

An embodiment of the present invention includes an electronic trip unit with the block diagram as shown in figure 1. The signal conditioning circuit includes an integrator and a gain amplifier. The output of which is fed to the microcontroller where an inbuilt ADC samples the signal and computes the RMS value of the sinusoidal signal. Select buttons are provided for providing the user efficient Navigation and Protection / System Settings control. Under the occurrence of an Electrical fault, the ETU issues a trip signal which causes the circuit breaker to discontinue the electrical flow with a delay depending on the time discrimination settings.

The microcontroller records the fault details along with the time stamp and stores it in the EEPROM for future fault diagnosis. For the convenience of the user, Modbus communication (as shown in Fig 3.) is provided for the user to control / monitor the ETU on a PC-HMI. The LCD display is controlled by interfacing it directly with the controller without requiring a driver. The functionality of the driver is emulated in the firmware by reversing the voltage polarity periodically so that a zero net voltage is applied to the device. This is done to prevent irreversible electrochemical action from damaging the display. This firmware controlled display provides a low cost display and requires lower number of I/O pins of all glass LCDs

As seen in Figure 2, the LCD has 4 COM inputs and 8 segment inputs, requiring 12 I/Os on the microcontroller. The LCD is supplied with AC signals, typically square waves. The LCD segments will become visible if the voltage difference between a COM input and a segment input is typically 3.3 V (VCC).

COM Inputs: The 4 COM inputs are each biased at ½ VCC. This is done to allow selected segments to be visible. All 4 COMs are sequentially enabled to produce one AC cycle each. The total time for all 4 COMs to cycle is set as per the required refresh rate of the LCD. This is fast enough so no flicker will be noticed, and still slow enough to prevent ghosting of the ‘off ‘segments.
To energize a segment, the waveform to that segment must be 180 degrees out of phase with its COM waveform. The voltage difference between the segment and COM signals will therefore be typically 3.3 V, which causes the segment to become visible after the refresh cycles. To de-energize (turn off) a segment, the COM and segment waveforms should be in phase with each other while that segment’s COM is active, that is, not at high Impedance state. So, a LCD with all segments OFF will have the segment inputs in phase with each COM input.
In the present invention, a single microcontroller would perform the tasks of signal monitoring and metering, providing protection against electrical fault with indication and event record, communicating to a remote location and driving an LCD without using an intermediate driver. The LCD display is controlled by interfacing it directly with the controller without requiring a driver. The functionality of the driver is emulated in the firmware providing a low cost display that requires lower number of I/O pins.

An energy management system which provides advanced metering - current, voltage, frequency, power, power factor, energy, harmonics and phase sequencing. The single chip solution offers the provision to reset the display under the abnormal condition of ‘Display Hanging’. The present invention relates to implementation of a highly integrated single chip solution for an Electronic Trip unit of a circuit breaker. A single microcontroller would perform the tasks of signal monitoring and metering, providing protection against electrical fault with indication and event record, communicating to a remote location and driving an LCD without using an intermediate driver.

Implementation of single chip solution for Monitoring, Protection, Fault Recording, Navigation, Communication and Display Control of Electronic Trip Units used in Circuit breakers is provided using this invention. The present invention relates to implementation of a highly integrated single chip solution for an Electronic Trip unit of a circuit breaker. A single microcontroller would perform the tasks of signal monitoring and metering, providing protection against electrical fault with indication and event record, communicating to a remote location and driving an LCD without using an intermediate driver.

ADVANTAGES:

1. Single IC performing display driver function using GPIO.

2. Single IC performing DSP function without separate engine.

3. This IC working at higher frequency yet compensating for increased current by moving into sleep mode frequently.

4. This IC has the flexibility of incorporating the updated functionalities in future course without calling for change in core architecture. ,CLAIMS:1. An electronic trip unit for circuit breaker(s), said unit comprising:
a signal conditioning module for providing an input signal;
a select switch(s) for providing controlled setting for navigation and protection to said electronic trip unit;
a controller means comprising a converting means, and a memory;
wherein said controller means connected to signal conditioning module and said select switch(s), facilitating signal monitoring and metering, providing protection against an electrical fault with an indication and recording, and communicating to a remote location and driving an display means.
2. The unit as claimed in claim 1, wherein said controller means comprises a memory for facilitating recording of faults along with time stamp for diagnosis of fault.
3. The unit as claimed in claim 1further comprising a communicating means for controlling and monitoring of said circuit breaker on said display means.
4. The unit as claimed in claim 3, wherein said communicating means is a modbus communication.
5. The unit as claimed in claim 1, wherein said display means is controlled by said controller means by direct interfacing of said display means.
6. The unit as claimed in claim 1, wherein said display means is controlled by a firmware controller means.
7. The unit as claimed in claim 1, wherein said display means is LCD display, PC-HMI and the like.

8. The unit as claimed in claim 1, wherein said controller means is a microcontroller.