Claims:We Claim:
1. A relay circuit assembly (100, 200) for elimination of induced parasitic voltage, comprising:
- a plurality of first set of relay coils (R1, R2, R3,……,RN) arranged parallel to each other with each of the plurality of first set of relay coils (R1, R2, R3,……,RN) having a normally open (NO) contact and a normally closed (NC) contact with the ‘NO’ contact connected to a supply voltage; and
- a plurality of second set of relay coils (K1, K2, K3,….,KN) arranged parallel to each other with each of the plurality of second set of relay coils (K1, K2, K3,….,KN) connected to each of the plurality of first set of relay coils (R1, R2, R3,……,RN), respectively, via a single multicore cable,
- wherein normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) is extended to a neutral line through a separate core in the single multicore cable in order to eliminate an induced parasitic voltage in the relay circuit assembly (100) during long distance transmission of AC voltage while in operation.
2. The relay circuit assembly (100, 200) as claimed in claim 1, wherein the single multicore cable extends beyond a length of 500 metre.
3. The relay circuit assembly (100) as claimed in claim 1, wherein the normally open (NO) and the normally closed (NC) contact in each of the plurality of first set of relay coils (R1, R2, R3,……,RN) are separate with respect to each other, alternatively are provided with a changeover.
4. The relay circuit assembly (100) as claimed in claim 3, wherein the normally open (NO) and the normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) are separately connected to a common terminal ‘C1’ and ‘C2’, respectively, with ‘C1’ and ‘C2’ being shorted with each other.
5. The relay circuit assembly (200) as claimed in claim 3, wherein a changeover type is provided for the normally open (NO) and the normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) with the normally open (NO) and the normally closed (NC) being connected to a single common terminal ‘C1’.
6. The relay circuit assembly (100, 200) as claimed in claim 1, wherein the relay circuit assembly (100, 200) is connected between a motor control center (MCC)/ switch gear (SWGR) and a distributed control system (DCS)/ programmable logic controller (PLC).

Dated this 23rd day of March, 2022

SOMA RANI MISHRA
PATENT AGENT
IN/PA – 1159
OF L. S. DAVAR & CO.,
APPLICANT’S AGENT

, Description:A RELAY CIRCUIT ASSEMBLY FOR ELIMINATION OF INDUCED PARASITIC VOLTAGE

FIELD OF THE INVENTION

[0001] The present disclosure relates to a relay circuit assembly and an associated electrical control scheme for reduction/removal of induced parasitic voltages in AC relay circuits. In particular, the present disclosure relates to the scheme, where the scheme employs extension of neutral wire of a supply line to the coil through either separate contacts or a changeover contact.

BACKGROUND OF THE INVENTION

[0002] The background of the invention relates to use of AC relays in LT/HT (Low Tension/High Tension) switch gears in which long cabling is used. AC relays are used in wide variety of circuits from complex to simple ones. They can be used in the place of other forms of switches, or they can be specifically designed based on different factors like required amperage.
[0003] Now, the relays comprises of two main circuits, namely, one at a primary side and another at a secondary side. The primary circuit provides control signal to operate a relay and this could be controlled by a manual switch or some other type of sensor. On the other hand, the secondary circuit contains a load that is to be controlled. On the primary circuit, there is provided an electromagnetic coil which create magnetic field when the current passes through it. This magnetic field can be controlled by simply controlling the current passing through it. Moreover, there is provided an armature pivoted at an end of the electromagnetic coil. When the electromagnet energises it attracts armature and when it de-energises, the armature goes back to its original position with the help of a spring, connected to armature. There are two types of relays present in the electromagnetic coil, namely a normally open (NO) and a normally closed (NC). In normally closed (NC) relay, the circuit on the secondary side closes when the armature is detached from the electromagnet.
[0004] Due to an increased length of the multicore wire, parasitic voltages are getting induced in the cores of the multi core cables by an electromagnetic induction effect happening inside the multicore cable, when the wires are placed very nearby.
[0005] At a particular time, as shown in Figure 1, some of the relays are energised and some are not which is connected together in the multicore cable coming from a switch gear (SWGR)/ motor control center (MCC) to a distributed control system (DCS)/programmable logic controller (PLC) based relay panels for contact interrogation. Even when the contact in SWGR/MCC is open, there is no conduction of current through multicore wire but due to the electromagnetic induction an unwanted voltage is getting induced in the open wires, also known as parasitic induced voltage. Due to this parasitic induced voltage, the relay is unable to drop out even when the contact in the field is open. Moreover, parasitic induced voltage is not favourable in the circuit as it can damage AC relays, or it can also result in malfunctioning of other devices.
[0006] Presently the malfunctioning of AC relays due to parasitic induced voltage is solved by using special relays which employs RC circuits internally or by use of an external RC circuit along with the normal AC relay. Another way to solve this issue is to have higher voltage rating relays than the applied voltage in the relay control scheme. However, these techniques are relatively costly and also large quantity (more than 600 numbers) of these relays are used in each projects as per the field requirements. Therefore this is not a feasible method to overcome the above mentioned challenges.

[0007] Towards this direction, the present disclosure proposes a relay circuit assembly and a scheme to overcome the above-mentioned drawbacks/disadvantages with cheaper alternatives and can easily be used in different circuits.

OBJECTIVES OF THE INVENTION

[0008] It is an object of the present subject matter to overcome the aforementioned and other drawbacks existing in the prior art systems.

[0009] It is a principal object of the present subject matter to provide a scheme that eliminates parasitic induced voltage in multi core control cables.

[0010] It is another significant object of the present subject matter to provide a scheme that does not require add on components to the normal relays to avoid malfunctioning of AC relays.

[0011] It is another object of the present subject matter to provide a scheme that will help in eliminating voltage fluctuation due to parasitic induced voltage.

[0012] It is yet another object of the present subject matter to provide a scheme that is cost effective in nature.

[0013] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taking into consideration with accompanied drawings in which preferred embodiments of the present subject matter are illustrated.

SUMMARY OF THE INVENTION

[0014] This summary is provided to introduce a scheme related to reduction/removal of induced parasitic voltages in AC relay circuits. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0015] According to the present subject matter, there is provided a plurality of first set of relay coils (R1, R2, R3,……,RN) arranged parallel to each other with each of the plurality of first set of relay coils (R1, R2, R3,……,RN) having a normally open (NO) contact and a normally closed (NC) contact with the ‘NO’ contact connected to a supply voltage, and a plurality of second set of relay coils (K1, K2, K3,….,KN) arranged parallel to each other with each of the plurality of second set of relay coils (K1, K2, K3,….,KN) connected to each of the plurality of first set of relay coils (R1, R2, R3,……,RN), respectively, via a single multicore cable. Herein, normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) is extended to a neutral line through a separate core in the single multicore cable in order to eliminate an induced parasitic voltage in the relay circuit assembly during long distance transmission of AC voltage while in operation.
[0016] In an aspect, in the relay circuit assembly, the single multicore cable extends beyond a length of 500 meter.
[0017] In an aspect, in the relay circuit assembly, the normally open (NO) and the normally closed (NC) contact in each of the plurality of first set of relay coils (R1, R2, R3,……,RN) are separate with respect to each other, alternatively are provided with a changeover.
[0018] In an aspect, in the relay circuit assembly, the normally open (NO) and the normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) are separately connected to a common terminal ‘C1’ and ‘C2’, respectively, with ‘C1’ and ‘C2’ being shorted with each other.
[0019] In an aspect, in the relay circuit assembly, a changeover type is provided for the normally open (NO) and the normally closed (NC) contact of each of the plurality of first set of relay coils (R1, R2, R3,……,RN) with the normally open (NO) and the normally closed (NC) being connected to a single common terminal ‘C1’.
[0020] In an aspect, the relay circuit assembly is connected between a motor control center (MCC)/ switch gear (SWGR) and a distributed control system (DCS)/ programmable logic controller (PLC).

[0021] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.

[0022] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which numerals represent like components.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING(S)
[0023] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number or alphabets identifies the figure in which the reference number or alphabets first appears. The same numbers and alphabets are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which

[0024] Figure 1 illustrates a scheme of existing relay circuit scheme having DCS relay coil connected to MCC relay contacts;

[0025] Figure 2 illustrates an exemplary scheme of a relay circuit assembly for eliminating induced parasitic voltages, in contacts where change over type is not available in accordance with an exemplary embodiment of the present disclosure; and

[0026] Figure 3 illustrates an exemplary scheme of a relay circuit assembly for eliminating induced parasitic voltages, in contacts where change over type are available in accordance with an exemplary embodiment of the present disclosure.

[0027] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF INVENTION WITH REFERENCE TO THE DRAWINGS OF THE PREFERRED EMBODIMENTS

[0028] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such a detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0029] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0030] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.

[0031] The present disclosure relates to a relay circuit assembly (100) electrical control scheme for reduction/removal of induced parasitic voltages in AC relay circuits. The scheme employs extension of neutral wire of supply line to the coil through either through separate contacts or through a changeover contact.

[0032] Figure 2 illustrates an exemplary scheme of a relay circuit assembly (100) for eliminating induced parasitic voltages, in contacts where change over type is not available in accordance with an exemplary embodiment of the present disclosure. In an aspect, as shown in Figure 2, a plurality of first set of relay coils (R1, R2, R3,……,RN) is arranged parallel to each other with each of the plurality of first set of relay coils (R1, R2, R3,……,RN) having a normally open (NO) contact and a normally closed (NC) contact. The ‘NO’ contact is connected to a supply voltage.

[0033] In an aspect, there is provided a plurality of second set of relay coils (K1, K2, K3,….,KN) arranged parallel to each other with each of the plurality of second set of relay coils (K1, K2, K3,….,KN) connected to each of the plurality of first set of relay coils (R1, R2, R3,……,RN), respectively, via a single multicore cable.

[0034] In an aspect, ‘NO’ and ‘NC’ denotes normally open contact and normally close contact of A and A’, respectively. C1 and C2 are the common terminals for ‘NO’ and ‘NC’ contacts of A, similarly C1’ and C2’ are the common terminals for NO and NC contacts of A’.

[0035] In an aspect, herein, the plurality of second set of relay coils (K1, K2, K3,….,KN) are present in a DCS/PLC panel system for contact interrogation. ‘A’ and ‘A’’ are relay in the MCC/SWGR panel, ‘Z1’, ‘Z2’ and ‘Z3’ are the long wires (preferably more than 500-meter length multi core control cable). ‘Z2’ wire connects the DCS/PLC relay coil to MCC/SWGR relay contacts with an AC supply being connected to ‘NO’ contact of relay ‘A’ and ‘A’’ in MCC/SWGR via a ‘Z1’ wire. One side of coil of the plurality of second set of relay coils (K1, K2, K3,….,KN) is connected to neutral of supply via a ‘Z3’ wire.

[0036] Now the idea of incorporation of the ‘NC’ or ‘NO’ contacts are to eliminate the induced parasitic voltage which is otherwise transmitted to all the relays connected in the existing arrangement. As shown in Figure 2, dotted lines are connections made for eliminating the induced voltages in the cable during long distance transmission of AC voltages. With these connections C1 and C2 are short-circuited with A, similarly C1’ and C2’ are also short-circuited with A’. ‘NC’ contact is wired to the neutral of the AC supply through a separate core in the same multi core cable, which is used for wiring an interrogating contact. ‘NC’ contacts of A, A’ are also looped in a fashion as shown in Figure-2.

[0037] In an aspect, during operation, when the A of the plurality of first set of relay coils (R1, R2, R3,……,RN) is getting energized via the ‘Z1’ wire ‘NO’ and ‘C1’ makes a close contact and the resulting voltage gets transmitted to the coil of relay ‘K1’ of the plurality of second set of relay coils (K1, K2, K3,….,KN) of making relay of ‘K1’ of the plurality of second set of relay coils (K1, K2, K3,….,KN) contacts in pick up condition.

[0038] In an aspect, during the pickup condition, all combinations of ‘A’- K2’, etc. of the plurality of first set of relay coils (R1, R2, R3,……,RN) and the plurality of second set of relay coils (K1, K2, K3,….,KN) can be in energized or in de energized conditions, depending on the process requirements. Due to this energized condition, normally a current flows through the wires connected resulting in an unwanted induced voltage.

[0039] In an aspect, at this point upon de-energizing the relay coil R1 of the plurality of first set of relay coils (R1, R2, R3,……,RN), the contacts between ‘NO’ and ‘C1’ contact gets disconnected. However, as discussed, there remains a voltage induced across the coil of relay ‘K1’ of the plurality of second set of relay coils (K1, K2, K3,….,KN). This voltage is getting induced due to a phenomenon of electromagnetic induction happening at the multi core cable due to long distance of ‘Z1’ and ‘Z2’. The proposed scheme provides a path (shown in dotted lines in Figure 2) that helps to de energize the coil and directs the resulting unwanted parasitic voltage towards the ‘NC’ of relay ‘A or ‘A’’, where this unwanted voltage gets out of the relay circuit and connects with the neutral line following a flow path as shown via dotted line in Figure2.

[0040] Figure 3 delineates an exemplary scheme of the relay circuit assembly (200) for eliminating the induced parasitic voltages, in contacts where change over type is not available in accordance with an exemplary embodiment of the present disclosure. Herein, the components of the circuit as followed in the proposed scheme is same as discussed in Figure 2 and are not iterated here for the sake of brevity.

[0041] In an aspect, as shown in Figure 3, there are provided change over contacts across C1 and C1’. ‘NO’ is the normally open contact of A and A’. ‘NC’ is the normally close contact of A and A’ and C1 and C1’ are the common contacts of A and A’. Due to the presence of changeover contacts, there is no requirement of C2 here unlike depicted in Figure 2.

[0042] In an aspect, the parasitic voltage developed as a result of the electromagnetic induction flows out from the relay of the plurality of first set of relay coils (R1, R2, R3,……,RN) following the path as shown with the help of dotted lines in Figure 3. Herein, ‘NC’ contact is wired to the neutral of the AC supply through a separate core in the same multicore cable that is used for wiring the interrogating contact. Moreover, ‘NC’ contacts of A and A’ is looped in a fashion as shown in Figure 2.

[0043] It is to be noted in this context, that the proposed scheme discussed in the present disclosure can be extended to any number of relays, which are connected via a single multi core cable from the MCC to the DCS/PLC.
[0044] Working of the invention has been discussed herein above with reference to Figure 2 and Figure 3, respectively.

Test Results
[0045] The test results are mentioned initially with reference to the existing arrangement as shown in Figure 1 followed by solving the problem as disclosed in the present invention.
[0046] According to Figure 1 ten (10) number of relays (R1, R2, ..R10) is connected in a single 12Pair multi core control cable from DCS to MCC, at a site where this combination of relays and distance between MCC and DCS is more than 500 meters.
[0047] All the relays (R1, R2,……,R10) are located at MCC and at a distance of more than 500 meter from the DCS panels. These relays (R1, R2,……..,R10) coils are energised at MCC and contacts are wired to DCS for interrogation to the coil of DCS relays (K1, K2,……,K10). The length of the single 12Pair multi core control cable is more than 500 meters. When any of the relays in MCC (R1, R2,……..,R10) are energised, 110V AC is extended to the coils of relays in DCS (K1, K2,….,K10) thereby energising the relays in DCS. If Relay ‘R1’ is energised in MCC corresponding relay K1 is energised at DCS. Similar situation occurs in case of K2-R2, K3-R3, K4-R4, K5-R5, K6-R6, etc. as well.
[0048] Now, at one particular time, when K1, K2, K3, K4, K5, K6 are energised in MCC, corresponding relays R1, R2, R3, R4, R5, R6 are energised at DCS. However, when K1 de energises in MCC, R1 does not get de-energised in the DCS, due to parasitic induced voltages in the multi core conductors (at this time conductors of K2,K3,K4,K5,K6 were energised).
[0049] At this juncture, a new scheme of connecting one of the spare core in the single 12Pair multi core cable to the neutral connection of the power supply in DCS has been introduced as disclosed in the present invention. All the relays in MCC (R1, R2,……,R10) were looped for NC contacts (as shown in Figure 2/Figure 3) and connected to the neutral core wire. By doing so the parasitic induced voltage gets discharged through the neutral wire to the power supply neutral. This allows the DCS side relay ‘K1’ to de energise whenever the corresponding relay de energises in MCC. The same has been tested for other combinations of relays and the arrangement was found in order. The voltage across the relay (K1, K2,….,K10) coil is found dropping to zero with the introduction of neutral wire connection.
[0050] In contrast, with an existing solution of RC circuits the voltage has been found to drop to some lower value and the small residual voltage remains across the coil.

Advantages
[0051] The relay circuit assembly (100, 200) as discussed in the present disclosure is having the following advantages:
a) Eliminates induced parasitic voltage in AC relay.
b) Facilitates the AC relay to operate reliably.
c) The proposed scheme provides an economical solution to the existing challenges by reducing cost of extra RC circuits or usage of special relays with inbuilt RC circuits.

[0052] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various systems that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.

[0053] Although embodiments for the present subject matter have been described in language specific to package features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/device of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

[0054] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone,
[0055] C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.).
[0056] In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0057] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.