FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Arc Runner for electrical switching device
2. APPLICANT(S)
(a) NAME : Larsen and Toubro Ltd.
(b) NATIONALITY: Indian
(c)ADDRESS : L&T House, Ballard Estate, Mumbai-400 001, India.
3. PREAMBLE TO THE DESCRITION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble -"I/We claim" on separate page)
6. DATE AND SIGNATURE (to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the separate page)
Note:
*Repeat boxes in case of more than one entry
*To be signed by the applicant(s)or the authorized registered patent agent
*Name of the applicant should be given in full, family name in the beginning
*Complete address of the applicant should be given stating with postal index no. / code, state and
country
* Strike out the column which is/are not applicable

FIELD OF THE INVENTION
[001] The invention relates to switching devices, and more particularly to an arc runner arrangement for electrical switching devices. BACKGROUND OF THE INVENTION
[002] Electrical switching apparatus, such a switch disconnector provides safety isolation for
any low voltage circuits and suitable for diverse applications in motor control centers,
switchboards and as main switches in various equipment and machines. These switches are ideal
for breaking stalled motor current, switching highly inductive loads, capacitor banks, DC loads
etc. Typically, switching devices comprises a housing, a contact arrangement including a fixed
contact and a moving contact enclosed within the housing, an operating mechanism to operate
the contacts, and an arc chute to quench the arc.
[003] The operating mechanism of the switching device during the fault condition will separate
the contacts, and at this instant an arc is generated and an arc root is formed between the fixed
contact and the moving contact, and the arc is pushed into the arc chute to quench the arc.
However life of contacts of device and erosion rate of the contacts is dependent on arc quenching
period i.e. the amount of time taken to extinguish the arc. The arc quenching period is dependent
on how fast the arc runner drags the arc away from the contact region.
[004] Typically, the arc quenching period is 15ms in conventional switching devices. Hence the
arc takes time to penetrate the arc chute. This leads to contact erosion and decrease life of the
contacts.
[005] In view of the above, there is a need in the art to reduce erosion of the contacts and
increase life of the contacts.

SUMMARY OF THE INVENTION
[006] Accordingly, the present invention in one aspect provide an arc runner arrangement for an electrical switching device, the switching device having a fixed contact, a moving contact connected to the fixed contact when the device is in ON condition, wherein an arc runner is provided on the fixed contact, the arc runner has a curved edge covering edge of the fixed contact such that the arc runner increases mobility of the arc and drags the arc towards the curved edge when the moving contact opens.
[007] In another aspect, the present invention provides an electrical switching device, the switching device having a contact arrangement, the contact arrangement comprising fixed and moving contacts, wherein an arc runner is provided on the fixed contact, the arc runner has a curved edge covering the fixed contact edge such that the arc runner increases mobility of the arc and drags the arc towards the curved edge when the moving contact opens. BRIEF DESCRIPTION OF THE DRAWINGS
[008] Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows a contact arrangement with an arc runner arrangement in accordance with an embodiment of the invention.
Figure 2 shows a fixed contact with the arc runner arrangement in detail in accordance with an embodiment of the invention.

Figure 3 shows an arc runner in detail in accordance with an embodiment of the invention.
Figure 4 shows an electrical switching device in accordance with an embodiment of the invention
DETAILED DESCRIPTION OF THE INVENTION
[009] Various embodiments of the present invention provide an arc runner arrangement for an electrical switching device, the switching device having a fixed contact, a moving contact connected to the fixed contact when the device is in ON condition, wherein an arc runner is provided on the fixed contact, the arc runner has a curved edge covering edge of the fixed contact such that the arc runner increases mobility of the arc and drags the arc towards the curved edge when the moving contact opens.
[010] Figure 1 shows a contact arrangement 100 in accordance with an embodiment of the invention. Contact arrangement 100 includes a fixed contact 102 and a moving contact 104 and an arc runner 106.
[011] In an embodiment of the invention, fixed contact 102 has arc runner 106. Fixed contact 102 is shown in detail in figure 2. In an embodiment of the invention, arc runner 106 is positioned such that when an arc is generated, the arc runner increases the mobility of the arc. [012] In an embodiment of the invention, arc runner 106 is positioned on fixed contact 102 near edge of fixed contact 102 i.e. near breaking point of contacts 102 and 104. In an embodiment of the invention, arc runner is positively attached to fixed contact 102.
[013] In an embodiment of the invention, arc runner 106 has a curved edge 108 as shown in figure 3. Curved edge 108 increases mobility of the arc, and drags the arc towards curved edge 108 when moving contact 104 opens. Advantageously, curved edge 108 reduces the arc immobility time. According to the present invention, arc runner 106 is provided nearer to the

breaking point so that when an arc is formed, the arc will jump quickly on arc runner 106 from position (i) to position (ii) as shown in figure 1 due to less gap and less reluctance of material. [014] In an embodiment of the invention, arc runner 106 is electro-magnetic material. The electro-magnetic material increases the blowout force and thereby reduces arcing time.
Figure 4 shows an electrical switching device 400 in accordance with an embodiment of the invention. Electrical switching device 400 includes a top housing 402, a bottom housing 404,
[015] a contact arrangement having- a fixed contact 406 and a moving contact, an arc chute
408 for each of pair of contacts and a plurality of phase barriers 410.
[016] Contact arrangement of electrical switching device 400 shown in figure 4 is similar to
contact arrangement 100 with arc runner 106 shown in figure 1. In an embodiment of the
invention, fixed contact has an arc runner. The arc runner is positioned such that the arc runner
increases mobility of the arc, increasing the arc voltage and reducing the arc immobility time.
Further the arc runner has a curved edge the curved edge increases the mobility of the arc and
drags the arc towards the curved edge when the moving contact opens, further reducing
immobility time of the arc.
[017] In an embodiment of the invention, electrical switching device 400 is capable of
interrupting alternating current and direct current at high voltages (more than 415V).
[018] In an embodiment of the invention, contact arrangement with arc runner can be adapted
to electrical switching devices such as switch disconnector (SD), miniature circuit breaker
(MCB), moulded case circuit breaker (MCCB), air circuit breaker (ACB) and switch
disconnector with fuse (SDF) etc.
[019] In an embodiment of the invention, during a fault condition, contacts (fixed contact and
moving contact) are opened and an arc is formed. The fixed contact has an arc runner positioned
such that mobility of arc increases. Further the arc runner has a curved edge, the curved edge

increases mobility of the arc to move away from the contacts, elongating the arc and thereby
increasing the arc voltage and reducing the arc immobility time. Thus the contact arrangement
with arc runner, increases motion of the arc, increases length of the arc and hence increases arc
voltage to quench the arc.
[020] According to the present invention, contact arrangement with arc runner reduces the arc
quenching period by at-least 9 ms i.e. it reduces the arc quenching period from 15ms (prior-art)
to 6ms.
[021] Advantageously, the arc runner arrangement of the present invention reduces arc
quenching period, reduces erosion rate of contacts thereby increasing life of the contacts.
[022] While the present invention has been described with respect to certain embodiments, it
will be apparent to those skilled in the art that various changes and modification may be made
without departing from the scope of the invention as defined in the following claims.

We claim:
1. An arc runner arrangement for electrical switching device, the device comprising;
At least one terminal;
A moving contact connected to the said terminal when device is in ON condition;
An arc runner connected to the said terminal; the said arc runner is bent to cover the
terminal edge;
Wherein, the arc runner drags the arc towards bend portion when the moving contact opens.
2. The contact arrangement as claimed in claim 1, wherein the arc runner is electro
magnetic material.