FIELD OF INVENTION
[001] The present disclosure relates to a contactor used in motor starter. More
specifically, the present invention relates to a DC coil with a latch operated
contactor& Digital Overload relay.
BACKGROUND
[002] Switching mechanisms form the basis for operation of any appliance.
Electronic switching mechanisms mainly consist of contactors and relays which have
long been used in switching applications including motor starters, auto changeover,
lightning automation devices, etc.
[003] Motor starters are used for safe operation of three phase motors and therefore,
a motor starter which is able to operate in a wide band of voltages is desirable for an
overall protection of motor. However, relays are not considered to be a preferred
choice for switching in heavy load applications as there is a constant risk of short
circuit. Moreover, conventional contactors also pose disadvantages such as chattering
and coil burning for operation of low as well as high voltages which ultimately confer
inconvenience to the customer.
[004] Therefore, a cost effective technology which aims at overcoming the threats
posed by traditional switching mechanisms with applicability over a wide voltage
range is needed for safe and secure operation of appliances.
SUMMARY
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[005] In accordance with an embodiment, a motor starter is provided with a DC coil
latch operated contactor for switching a motor. The contactor includes two or more
DC Coils. The first coil has a first output terminal NO and a common output terminal
C while a second coil has a second output terminal NC and the common output
terminal C (or the third terminal C).The third terminal C is formed via a connection
strip disposed between the first and second coil. The first output terminal NO of the
contactor along with the common output terminal C provides a first output(normally
open connection) during one phase of power supply while the common output
terminal C and the second output terminal NC of the contactor provides a second
output (normally closed connection) during another phase of the power supply.
BRIEF DESCRIPTION OF DRAWINGS
[006] The summary above, as well as the following detailed description of
illustrative embodiments, is better understood when read in conjunction with the
appended drawings. For the purpose of illustrating the present disclosure, exemplary
constructions of the disclosure are shown in the drawings. However, the disclosure is
not limited to specific methods and instrumentalities disclosed herein. Moreover,
those in the art will understand that the drawings are not to scale.
[007] FIG. 1 is an exemplary architecture of a motor starter in accordance with an
embodiment of the present disclosure.
[008] FIG. 2 is an exemplary depiction of the PMC in accordance with an
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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[009] Prior to describing the invention in detail, definitions of certain words or
phrases used throughout this patent document will be defined: the terms "include" and
"comprise", as well as derivatives thereof, mean inclusion without limitation; the term
"or" is inclusive, meaning and/or; the phrases "coupled with" and "associated
therewith", as well as derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or with, couple to or with,
be communicable with, cooperate with, interleave, juxtapose, be proximate to, be
bound to or with, have, have a property of, or the like; Definitions of certain words
and phrases are provided throughout this patent document, and those of ordinary skill
in the art will understand that such definitions apply in many, if not most, instances to
prior as well as future uses of such defined words and phrases.
[0010] Wherever possible, same reference numbers will be used throughout the
drawings to refer to same or like parts. Moreover, references to various elements
described herein are made collectively or individually when there may be more than
one element of the same type. However, such references are merely exemplary in
nature. It may be noted that any reference to elements in the singular may also be
construed to relate to the plural and vice-versa without limiting the scope of the
disclosure to the exact number or type of such elements unless set forth explicitly in
the appended claims.
[0011] Particular embodiments of the present disclosure are described herein below
with reference to the accompanying drawings, however, it is to be understood that the
disclosed embodiments are merely examples of the disclosure, which may be
embodied in various forms. Well-known functions or constructions are not described
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in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore,
specific structural and functional details disclosed herein are not to be interpreted as
limiting, but merely as a basis for the claims and as a representative basis for teaching
one skilled in the art to variously employ the present disclosure in virtually any
appropriately detailed structure.
[0012] The present invention devises a motor starter incorporating a DC coil with
latch operated contactor which would now be addressed as “pre-magnetic contactor
(PMC)” hereon. The utilization of a PMC aims at overcoming the disadvantages of
traditional contactors by preventing chattering in low voltage applications and burning
of coil in high voltage applications. Therefore, the motor starter disclosed in the
present invention intends to provide a safe operation for the users.
[0013] In an embodiment of the present invention, the operating voltage of the motor
starter is 170-460 VAC. The motor starter may possess an automatic or a manual
setup for its operation.
[0014] However, the PMC incorporated in the motor starter of the present invention
may also be utilized for switching over a wide range of voltages in various other
applications such as lighting, heating, capacitor banks, thermal evaporators and other
electrical loads.
[0015] FIG. 1 depicts an exemplary architecture of the motor starter panel 100 of the
present invention illustrating different components: a push button 102, controller 104,
an overload relay 106, a miniature circuit breaker (MCB) 108, a PMC 110 and a
connection strip 112.
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[0016] In an embodiment of the present invention, the motor starter panel 100 is a
fabricated sheet metal cabinet with a compact design.
[0017] The motor starter panel 100 includes one or more push buttons 102 in order to
switch the motor on/off. The push buttons 102 may be constructed of any material
without limitation, plastic or metal with a flat or an embossed surface in order to be
smoothly depressed or pushed. In an embodiment of the present invention, three
separate smooth push buttons 102 including start; stop and run buttons are disposed
on the motor starter panel 100 for starting, stopping and running the motor
respectively. The push buttons 102 are capable of tripping off the motor on a sharp
settable voltage and current limit.
[0018] The motor starter panel 100 may comprise a switch for mode selection (not
shown in the FIG 1) which provides a choice for automatic or manual operation of the
motor starter. In an embodiment of the present invention, the motor starter
automatically starts the motor whenever the power resumes in all three phases if the
automatic mode is selected, while in the manual mode, one can manually start and
stop the motor instantly with the help of separate push buttons 102.
[0019] The controller 104 is a starter controller which controls the operation of the
motor through the motor starter panel 100 in a predetermined way. In an embodiment,
the controller 104provides protection against, without limitation, phase reversal, phase
unbalance and single phase prevention in multi-phase devices. In an embodiment, the
controller 104 does not allow the motor to start if any of the phases does not have the
power or if any two phases gets reversed.
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[0020] The overload relay 106 is an electronics device that protects the motor from
over/under load& voltage. The overload relay 106 may consist microprocessor based
electronic device, which is getting into action on excess current or voltage by the
motor, causing them to activating the trip mechanism depending upon the current
setting of the overload relay 106. In an embodiment of the present invention, the
overload relay 106 is a microprocessor based overload relay with digital metering.
The digital meter monitors and displays without limitation, voltage as well as current
thereby providing protection against over voltage, under voltage, dry run and
overload.
[0021] In an embodiment of the present invention, the overload relay 106 provides
accuracy and precision for parameters like over voltage, under voltage, dry run,
overload, run hour, ampere, and volt meter as well as a facility to read and control
these parameters on display. The motor starter may have without limitation, in-built
hour meter, digital ammeter as well as digital voltmeter. In an embodiment, the relay
range is up to 90 ampere.
[0022] In an embodiment of the present invention, the MCB 108 disposed on the
motor starter panel 100 provides an additional protection against overload.
[0023] The motor starter panel 100 includes a PMC 110 having a cost effective
design with smooth and instant switching capabilities. The motor starter panel 100
also have a connection strip 112 which is used for aggregating input as well as output
lines.
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[0024] In an embodiment, the operation of PMC 110 requires an electrical pulse for
few seconds in the coil rather than a continuous supply thereby, increasing the shelf
life of the coil as well as making it suitable for high voltages applications (elaborated
in FIG. 2). Moreover, the PMC 110 also prevents chattering as well as coil burning
which makes it perfectly suited for any automation application such as residential,
commercial, industrial, etc.
[0025] FIG. 2 illustrates the PMC in a motor starter. The PMC 303 may include two
DC coils 303a and 303b which are coupled to each other via a connection strip 303c.
The inputs of the two DC coils 303a (first coil) and 303b (second coil) are coupled to
the AC supply 301 while the output of the first and second DC coils 303a and 303b
are shown as first output terminal NO 305a and second output terminalNC305c
respectively. A third terminal C 305b representing common is provided via the
connection strip.
[0026] The two coils operate in conjunction with each other along with connection
strip to function as a magnetized switch.
[0027] In an embodiment of the present invention, the PMC 303 has an AC supply
301 driven coil inputs. The first input terminal of the first DC coil 303a is coupled to
the positive terminal of the AC supply 301 while the second input terminal of the
second coil 303b is coupled to the negative terminal of the AC supply 301.
[0028] During the positive cycle of the AC supply 301, an electrical current passes
through the first DC coil 303a which is coupled to the first output terminal NO305a.
Due to this, an electromagnetic field is generated in the magnetized switch thereby
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energizing the magnetized switch. The first output terminal NO 305a with the third
terminal C305b acts as normally open connection. Likewise, during the negative cycle
of the AC supply 301, the second DC coil 303b coupled to the second output terminal
NC 305c is energized. The second output terminal NC 305c with the third terminal C
305b acts as normally closed connection.
[0029] The connection strip 303c placed between the two DC coils, constitutes a third
terminal is also exposed to the electromagnetic field and drives the switch
mechanism. For example, during the positive cycle, the connection strip 303c operates
along with the positive terminal and switches off the motor. Likewise, during the
negative cycle, the connection strip 303c operates along with the negative terminal
and completes the circuit thereby switching on the motor. The connection strip 303c
remains in that position until it receives another electromagnetic pulse which may be
in the opposite direction (depending upon the positive and negative cycle). This action
may push the magnetized switch back to the other terminal.

CLAIMS:
We claim:
1. A motor starter system for operating a motor, the motor starter comprising:
a power source having a positive terminal and a negative terminal; and
a pre-magnetic contactor for instant switching of the motor, the pre-magnetic
contactor comprises:
a first coil having a first input terminal and a first output terminal NO, the first
input terminal coupled to the positive terminal;
a second coil having a second input terminal and a second output terminal NC,
the second input terminal coupled to the negative terminal; and
a connection strip disposed between the first and second coils, the connection
strip acts as a third terminal(C)which works with the first output terminal or the
second output terminal under the influence of an electromagnetic field
generated by the first or the second coil respectively to operate the motor.
2. The motor starter as claimed in claim 1, wherein the first coil and/or the second
coil is a DC coil.
3. The motor starter as claimed in claim 1, wherein the pre-magnetic contactor is
coupled to a microprocessor based overload relay with digital metering for
monitoring and controlling the power source.
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4. The motor starter as claimed in claim 1, wherein the operating voltage of the
motor starter is in the range of 160-470 VAC.