DESC:TECHNICAL FIELD

The present subject matter described herein, in general relates to circuit breakers and more particularly, to a current sensing coil with variable cross-section core for a current measurement coil used in particular transformer and inductor, and a circuit breaker trip unit.

BACKGROUND

Circuit breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it will make the circuit, carry current for a specified time and break the circuit under specified abnormal circuit conditions.

Circuit breakers are employed for current interruption. More particularly the circuit breakers are utilized to protect instruments from damage during adverse conditions prevailing during the operation of the circuit in which circuit breaker is employed. During adverse conditions like short circuit, the current rises to an alarmingly high level. This high current may cause damage to the parts in the electrical system. Hence during these conditions the circuit has to be opened to protect the system.

A circuit breaker can be manually opened and closed, as well as automatically opened to protect conductors or equipments from damage caused by excessive heating due to over current in abnormal conditions such as overload or short-circuit.

Switching devices like, molded case circuit breaker operating on the current limiting principle typically have a pair of solid stationary Electrical contacts joined by a solid moving electrical contact, which provides a path to carry the electrical current in the network.

A current sensor is a device that detects electrical current (AC or DC) in a wire, and generates a signal proportional to it. The generated signal could be analog voltage, current or even digital output. It can be then utilized to display the measured current in an ammeter or can be stored for further analysis in a data acquisition system or can be utilized for control purpose.

There are various available products like MCCB that efficient works to produce certain output but they have certain limitations. In general the module spaces are constrained by volume for compact products such as MCCB. Hence it will be difficult to obtain required outputs due to manufacturing and space constrains with symmetric cross section in the Rogowski former.

Further, there are various attempts in progress to enhance the output of the products like MCCB. One of the attempts is related to the efficient utilization of available Rogowski former or coil to enhance the output. Electric coils / Rogowski former or coil are well known, particularly as transformer and inductors or circuit breakers. They usually have a plurality of turns of an electrical conductor. Flows through the coil a time-varying electric current, respectively, a magnetic flux is generated inside the coil. Conversely, a time-varying magnetic flux generates an electric current in the coil.

A trigger for circuit breaker, so-called Maglatch move a ferromagnetic plunger which is held against a spring force from a magnetic field of a permanent magnet. The spring serves simultaneously as an energy store. If it exceeds a predetermined current value, a triggering of the circuit breaker, whereby a coil of a magnetic field is generated which compensates for the magnetic field of the permanent magnet in the region of the plunger. Characterized the plunger is moved to release the stored energy in the spring in the direction of its longitudinal axis, wherein the circuit breaker is tripped.

The coils are commonly wound on a bobbin, a copper wire. They have a relatively high weight and volume and a high use of materials, particularly because of the often required to achieve the desired inductance large number of copper wire coils.

Some of the arrangements of the available Rogowski former or coils available in prior-art patent documents are given below:

A prior-art patent document US 7078888 B2 discloses a Rogowski type current measuring device comprises at least three coils electrically connected in series and forming a closed polygon outline designed to surround a conductor to perform current measurement. The local inductance of at least one of the ends of said coils is greater than the local inductance towards the central part of said coils. (The proposed solution as disclosed in prior-art is shown in figure1). However it is desirable to have a closed looped coil as that reduced the probability of external noise injection which enables the coil in giving a better output.

A prior-art patent document US 7227441 B2 discloses an improved Rogowski coil is formed on a toroidal core made of a thermoplastic or other moldable material, the core having a preferably continuous groove or grooves extending around the core. The grooves correspond in size to magnet wire which registers within the grooves, thus controlling the specific location of the wires. The grooving may be helical. A return loop can be provided for return path cancellation, or a reverse winding can be added in a direction opposite to the direction of advancement of the main coil. In using the return loop, a resistive network can be added to improve the cancellation of the return path due to the effect of geometries. In addition, it can compensate for thermal and other variations. (The proposed solution as disclosed in prior-art is shown in figure 2). However due to grooves configuration in plastic part, number of turns per layer will be less occupied which in turn increase the total number of layers so as volume of the coil.

A prior-art patent document US 6018239 discloses a self powered axial current sensor for generating a signal which accurately represents a current in a power line includes, in one embodiment, a housing having a bus bar opening of substantially rectangular shape or round shape extending longitudinally there through. The housing also includes current sensor region, and a cover base wall which defines, with one of the retaining walls, a power core region, a current sensor core and center axis of bus bar opening. The current sensor further includes a power core and a power coil located in the power core region and positioned substantially symmetrically with respect to the center axis of bus bar opening. (The proposed solution as disclosed in prior-art is shown in figure 3 and figure 4). However sensors with this type of configuration will occupy less space in depth wise, hence space available for Rogowski coil becomes compact. So that it will be difficult to accommodate increased core area or high number of turns to produce higher desired output.

Apart from the above mentioned drawbacks in general the module spaces are constrained by volume for compact products such as MCCB. Hence it is difficult to obtain required outputs due to manufacturing and space constrains with symmetric cross section in the Rogowski former. Further, the flux fringing at the corners will be high in the symmetric formers and this by and large which increases the noise levels further.

Thus, in view of the above mentioned drawbacks there exists a need to provide a mechanism with a coil having large inductance with a small volume and material to enhance the output of the products like MCCB, which is advantageous at low current ratings or space constraint issues, and less sensitive to external disturbances.

SUMMARY

This summary is provided to introduce concepts related to a Rogowski coil with variable cross-section core in circuit breakers. This summary is not intended to identify essential features of the subject matter nor is it intended for use in determining or limiting the scope of the subject matter.

In one implementation, the present invention relates to a circuit breaker. More particularly, the invention is about the current measurement coil used in circuit breaker for sensing the current in MCCB.

In one implementation, the present invention describes a Rogowski coil with variable cross-section core which provides enhanced output which is advantageous at low current ratings or space constraint issues, and less sensitive to external disturbances.

In one implementation, the proposed invention provides an efficient and low-cost solution to enhance the output of the existing or new products like MCCB.

In one implementation, the flux fringing at the corners will be high in the symmetric formers and this by and large will be minimized by the present invention having a non symmetric ones as the higher cross sections will be able to induce the fringing flux to secondary voltage and thus reduce the noise levels further. The noise reduction is aided by progressive winding and also giving a compensation turn which is perpendicular to the rest of the windings.

Accordingly, in one implementation, a current sensing coil is disclosed. The coil comprises of a first material (1) with a variable cross-section core; and at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said winding (2) is wound on core of said first material (1).

In one implementation, a current sensing coil is disclosed. The coil comprises of a first material (1) with a variable cross-section core made of a dielectric material with an asymmetric profile; and at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said at least one winding of said second material (2) is wound on core of said first material(1) extending a flux by current flowing through, and vice versa by means of at least one turn of said at least one winding generating a flux passing current, and said flux fringing at corners of said at least one turn of said at least one winding is minimized in said first material(1) as the higher cross sections induces the fringing flux to a secondary voltage and reduces a noise levels.

BRIEF DESCRIPTION OF THE ACCOMPANYINGDRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 shows prior art of US patent no: 7078888 B2.

Figure 2 shows prior art of US patent No: 7227441 B2

Figure 3 shows prior art of US patent No: 6018239

Figure 4 shows prior art of US patent no: 6018239

Figure 5 Winded Rogowski coil with start 3 and end 4 wires and opening 5is shown, in accordance with an embodiment of the present subject matter.

Figure 6 cross-section view of figure5 is shown, in accordance with an embodiment of the present subject matter.

Figure 7 shows Rogowski former 1 of dielectric material with cross-section B higher than cross-section A is shown, in accordance with an embodiment of the present subject matter.

Figure 8 shows cross-section views along of figure 7is shown, in accordance with an embodiment of the present subject matter.

Figure 9 shows the Rogowski coil with primary conductor 6 passing through the opening 5 whose current is to be measured is shown, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Preferred embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

The terms and words used in the following description 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.

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.

In one implementation, an apparatus and method thereof for a Rogowski coil with variable cross-section core in circuit breakers

In one implementation, the present invention describes a Rogowski coil with variable cross-section core which provides enhanced output which is advantageous at low current ratings or space constraint issues, and less sensitive to external disturbances.

In one implementation, the current invention provides a Rogowski (current measuring coil) with variable cross section core which provides enhanced secondary output at reduced volume.

Accordingly, in one implementation, a current sensing coil is disclosed. The coil comprises of a first material (1) with a variable cross-section core; and at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said winding (2) is wound on core of said material (1).

In one implementation, a current sensing coil is disclosed. The coil comprises of a first material (1) with a variable cross-section core made of a dielectric material with an asymmetric profile; and at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said at least one winding of said second material (2) is wound on core of said first material(1) extending a flux by current flowing through, and vice versa by means of at least one turn of said at least one winding generating a flux passing current, and said flux fringing at corners of said at least one turn of said at least one winding is minimized in said first material(1) as the higher cross sections induces the fringing flux to a secondary voltage and reduces a noise levels.

In one implementation, said first material (1) is a non-magnetic material and has a permeability equivalent to an air.

In one implementation, said first material (1) is made of a dielectric material with an asymmetric profile.

In one implementation, said first material (1) has at least one larger cross-section area that accommodate more length of at least one winding of a second material (2) per unit length in comparison with the remaining cross-section area of said first material(1).

In one implementation, said wherein said second material (2) is a conducting material selected from a group comprising of copper (Cu), soft iron (Fe), enameled copper wire or copper based alloy, PVC insulated wires, PTFE insulated wires etc.

In one implementation, said coil enables a primary conductor (6) to pass through a center and measure current of said primary conductor (6).

In one implementation, said current sensing coil is enclosed by non-insulating material.

In one implementation, said first material (1) is a Rogowski former.

In one implementation, said current sensing coil is a Rogowski coil.

In one implementation, said current sensing coil has a plurality of said winding of said second material (2) which are disposed on a said first material (1) which is located on a primary conductor (6) passing through a center of said current sensing coil (5) whose current is to be measured.

In one implementation, said noise in the secondary voltage is minimized with a higher cross section area of said former (1) as a corner fringing is converted into an output.

Referring now to figure 5 illustrates a winded Rogowski coil with start (3) and end (4) wires and opening (5) is shown, in accordance with an embodiment of the present subject matter. In one implementation, figure 5shows toroidal Rogowski coil which comprises of a conducting material like copper (2) that is winded on core of non-magnetic material whose permeability is equivalent to air known as Rogowski former (1). The (3) and (4) are start and end of the winding respectively.

Referring now to figure 6 illustrates a cross-section view of the winded Rogowski coil is shown, in accordance with an embodiment of the present subject matter. In one implementation, figure 6 shows the cross sectional views the toroidal Rogowski coil as shown in figure 5. The figure 6 shows the toroidal Rogowski former (1) with variable cross-section. This may have higher inductance locally at larger cross-section area “B”. This ensures high secondary output w.r.to the symmetric cross-section core coil. Figure 1, also shows an opening (5) for the primary conductor (6) for which the current is to be measured.

Referring now to figure 7 illustrates a Rogowski former (1) of dielectric material with cross-section “B” higher than cross-section “A” is shown, in accordance with an embodiment of the present subject matter. In one implementation, figure 7shows the Rogowski former of the dielectric material such as plastic with an asymmetric profile is shown. From the figure 7, it is evident that the former cross-section “B” is higher than the cross-section “A”. Hence Cross-section “B” can accommodate more length of wire per unit length in comparison with cross-section “A” which provides higher inductance at “B” in comparison with symmetrically distributed toroidal core construction. So this arrangement gives higher secondary output in comparison with symmetric one. In other words for a given output non-symmetric construction occupies less space w.r.to symmetric type of arrangement.

Referring now to figure 8 illustrates cross-section views along of a Rogowski former (1) of dielectric material with cross-section “B” higher than cross-section “A” is shown, in accordance with an embodiment of the present subject matter. In one implementation, figure 8shows the cross-section views of Rogowski former along lines X-X and Y-Y respectively are shown.

Referring now to figure 9 illustrates the Rogowski coil with primary conductor (6) passing through the opening (5) whose current is to be measured is shown, in accordance with an embodiment of the present subject matter. In one implementation, figure 8shows the Rogowski coil with primary conductor (6) passing through the center of the coil (5) whose current need to be measured is shown. The coil (5) provides a noise free secondary output proportional to the current which passes through the primary conductor. Rogowski coil can be enclosed by non-insulating material (not shown).

In one implementation, the flux fringing at the corners will be high in the symmetric formers and this by and large will be minimized in the non symmetric ones as the higher cross sections will be able to induce the fringing flux to secondary voltage and thus reduce the noise levels further. The noise reduction is aided by progressive winding and also giving a compensation turn which is perpendicular to the rest of the windings.

In one implementation, current sensing coil with variable cross section core, Cross section of B limb must be greater than cross section A as shown in figure 7 or cross section area of A must be greater than cross section B to get the explained effect/advantage. Non-symmetric cross section provides higher secondary output for a given volume with respect to symmetric one. The present invention effectively utilizes the available non-symmetric space. The fringing flux at corners of former can be utilized to obtain secondary output with large cross-section B so as noise minimization in secondary output obtains aided by progressive winding and compensating turn.

Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features:

One feature of the invention is that, the proposed invention provides a noise reduction is aided by progressive winding and also giving a compensation turn which is perpendicular to the rest of the windings.

Another feature of the invention is that, the space or volume available for sensor which is non-symmetric is utilized in the efficient manner, in the present invention.

Yet another feature of the invention it that, the non-symmetric type of arrangement provided in the present invention, enables to provide higher secondary output for a given primary current.

Still another feature of the invention is that, the noise in the secondary output is minimized with the higher cross section in the B limb as the corner fringing is converted into output which does not effectively happen in symmetric former. This is further aided by the progressive winding and the compensation turn.

Although an apparatus and method thereof for a Rogowski coil with variable cross-section core in circuit breakers been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations an apparatus and method thereof for a Rogowski coil with variable cross-section core in circuit breakers.
,CLAIMS:1. A current sensing coil, comprising:
a first material (1) with a variable cross-section core;
at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said winding (2) is wound on core of said first material(1).
2. The current sensing coil as claimed in claim 1, wherein said first material (1) is a non-magnetic material and has a permeability equivalent to an air.
3. The current sensing coil as claimed in claim 1 and claim 2, wherein said first material (1) is made of a dielectric material with an asymmetric profile.
4. The current sensing coil as claimed in claims 1-3, wherein said first material(1) has at least one larger cross-section area that accommodate more length of at least one winding of a second material (2) per unit length in comparison with the remaining cross-section area of said first material(1).
5. The current sensing coil as claimed in claims1-4, wherein said at least one winding (2) is of a solid metallic wire, or an electrical braid, which is formed of said second material (2).
6. The current sensing coil as claimed in claims1-5, wherein said second material (2) is a conducting material selected from a group comprising of copper (Cu), soft iron(Fe),enameled copper wire or copper based alloy, PVC insulated wires, PTFE insulated wires.
7. The current sensing coil as claimed in claims 1-6enables a primary conductor (6) to pass through a center and measure current of said primary conductor (6).
8. The current sensing coil as claimed in claims 1-7 is enclosed by a non-insulating material.
9. The current sensing coil as claimed in claims 1-8, wherein said current sensing coil is a Rogowski coil.
10. The current sensing coil as claimed in claims 1-9, wherein said current sensing coil has a plurality of said winding of said second material (2) which are disposed on a said first material(1) which is located on a primary conductor (6) passing through a center of said current sensing coil(5) whose current is to be measured.
11. A current sensing coil, comprising:
a first material (1) with a variable cross-section core made of a dielectric material with an asymmetric profile;
at least one winding of a second material (2) formed with a start point (3) and an end point (4) of said at least one winding, wherein said at least one winding of said second material (2) is wound on core of said first material (1) extending a flux by current flowing through, and vice versa by means of at least one turn of said at least one winding generating a flux passing current, and
said flux fringing at corners of said at least one turn of said at least one winding is minimized in said first material(1)as the higher cross sections induces the fringing flux to a secondary voltage and reduces a noise levels.
12. The current sensing coil as claimed in claim 11, wherein said noise in the secondary voltage is minimized with a higher cross section area of said former (1) as a corner fringing is converted into an output.