FIELD OF THE INVENTION:
The present invention relates to a residual-current device (RCD). In particular, the
present invention relates to a compact two-module residual current circuit breaker
with overload protection (RCBO) with a toggle switch having switched neutral,
for use in distribution systems at the most downstream circuits such that it is fit
able in standard switch and socket outlets. More particularly, the invention relates
to a retrofittable twin-module residual circuit breaker device to provide overcurrent,
short-circuit and leakage current protection to one or more interconnected
electrical appliances.
BACKGROUND OF THE INVENTION
The RCBO is used for both protection of overload/short-circuit and leakage
current fault. Generally, the existing RCBOs are larger in size so that they are
suitable for distribution board, but cannot be installed in socket outlets for
localized or additional discriminatory protection at downstream level. The
switching devices in distribution boards are used to protect a wider range of
circuits in a premises. When there is any fault, the power goes off for the entire
group of devices which causes inconvenience and hindrance to other activities. In
case of tripping, the users need to go to the main distribution board every time to
reset the switching device, which is inconvenient as the distribution board is
sometimes located quite farther away. Moreover in such cases, the fault detection
is also difficult and time – consuming. Very often, frequent tripping of residual
current devices and the associated inconvenience is a reason to bypass crucial
leakage current protection. These problems can be overcome if RCBOs are
available for dedicated localized protection of downstream circuits and can be
installed in socket outlets nearer to the user.
-3-
Publication No. WO2009005374 (A1) relates to residual current circuit breakers.
The RCCB can be manufactured compactly, and can be fitted as a modular
component, along with other modular components, to assemble an electrical
socket with a 'trip' capability. The breaker as described above is small and
compact enough to be used with a PDL 500 or 600 size modules.
Indian Publication No. 3045/MUM/2009 relates to an improved arrangement for
tripping of single Modular Electronic RCBO. The tripping on a single modular
electronic RCBO can be done by a single trip pin in case of leakage as well as
short circuit condition.
Compact RCBOs are known, but conventional RCBOs occupy a large space and
are typically used for installation in distribution boards only. Those are not
suitable for installation in socket outlets for localized or additional discriminatory
protection at downstream level. Further compact MCBs or RCCB in 1 or 2
module standard socket size are available, but they either provide only
overcurrent/short-circuit protection or leakage fault protection but do not provide
all the protection.
To overcome the drawbacks of prior art, the present invention provides a RCBO
whose mechanism is incorporated in a compact design to occupy a small space
and which is enabled to detect localized or additional discriminatory leakage,
over-current and short-circuit, and provide protection at downstream level.
The present invention is directed to provide a compact 2-module Residual Current
Circuit Breaker with overload protection (RCBO) with a toggle switch having
switched neutral, which is fit able in standard switch and socket outlets. For
incorporating the mechanism within the small space constraints, design
optimization has been done.
-4-
OBJECTS OF THE INVENTION:
It is therefore an object of the present invention is to propose a retrofittable twinmodule
residual circuit breaker device to provide over-current, short-circuit and
leakage current protection to one or more inter-connected electrical appliances.
Another object of the invention is to propose a retrofittable twin-module residual
circuit breaker device to provide over-current, short-circuit and leakage current
protection to one or more inter-connected electrical appliances, which is compact
and can be mounted in downstream switchboards and wired in series such that the
incoming terminals of device are connected to phase and neutral wire coming
from the main distribution board and the outgoing terminals of the device are used
to supply phase and neutral points of downstream circuits.
A still another object of the present invention is to propose a retrofittable twinmodule
residual circuit breaker device to provide over-current, short-circuit and
leakage current protection to one or more inter-connected electrical appliances,
which is provided with a toggle switch having switched neutral and capable for
localized protection nearer to the point of application.
Yet another object of the present invention is to propose a retrofittable twinmodule
residual circuit breaker device to provide over-current, short-circuit and
leakage current protection to one or more inter-connected electrical appliances,
which provides additional discriminatory protection of downstream circuits, that
is to say, the device disconnects power supply only to a few connected circuits in
the region of fault and prevents other loads in the main distribution board from
going out of supply.
A further object of the present invention to propose a retrofittable twin-module
residual circuit breaker device to provide over-current, short-circuit and leakage
current protection to one or more inter-connected electrical appliances , which is
disposed nearer to the point of application and exhibits the advantages of easy
fault detection and easy resetting to the user.
-5-
SUMMARY OF THE INVENTION:
The present invention provides a compact two module residual current circuit
breaker with overload protection (RCBO) with a toggle switch having switched
neutral, which is fit able in standard switch and socket outlets. It can be used for
localized or additional discriminatory over-current, short-circuit and leakage fault
protection for few appliances as per requirement. In case of fault it only
disconnects power to a few connected circuits in the region of fault and prevents
other load in the premises from going out of supply. It includes the mechanism for
RCBO that has been incorporated in a compact design which would occupy a
small space such that the device can be easily fitted in the socket outlets. It is easy
to reset, being near to the user. Since it is used for few dedicated appliances, fault
detection is also easy.
In a preferred embodiment of the present invention, there is provided a
retrofittable twin-module residual circuit breaker device to provide over-current,
short-circuit and leakage current protection to one or more inter-connected
electrical appliances , which incorporates a toggle switch having switched neutral,
attachable to any standard switch and socket outlets. In order to incorporate the
complete RCBO device within a small space constraints such that its width is
limited to 2-module and height is limited to that of standard socket outlets.
One of the two modules is dedicated to a live pole and incorporates the
mechanism for overcurrent and short-circuit fault protection such as incoming and
outgoing terminals, a bimetal piece, an arc chute assembly, a contact assembly, a
solenoid. The other module is dedicated to a neutral pole and incorporates the
mechanism for leakage fault protection such as a PCB, a solenoid, a current
transformer (CT), incoming and outgoing terminals, a shroud, a test button
mechanism, and an indicating mechanism.
-6-
a) a phase wire is brought from the solenoid in the live pole, via a cut in the
chassis, to the neutral pole side, passing it through the CT and then it is
taken back to the live pole via the same cut in chassis, wherein the phase
wire is welded to the bimetal piece;
b) an incoming neutral wire also passes through the CT in the same direction,
both of these form the primary core of the current transformer;
c) the secondary core of the current transformer gives signal to the PCB
whenever there is a current leakage, which actuates the solenoid, which in
turns trips the device;
d) and a trip bar disconnects both the live and neutral poles together in case
of fault.
In another embodiment of the present invention, for overcoming the space
constraints, the test button mechanism has been uniquely designed such that there
is a direct spring linkage with a metallic pin in the PCB. On pressing a test button,
the springs short the phase and neutral internally, to pass a leakage current for
testing purpose.
In yet another embodiment of the present invention, the load and supply
terminals of the neutral pole have been brought to the same side and are staggered
with respect to each other, with a shroud between them giving electrical
clearance. These changes give space benefit for incorporating the PCB, the
current transformer, the solenoid, the test button mechanism and other RCD
circuitry. The neutral is switched and its moving contact being longer in size as
compared to the moving contact of the phase pole give advance of the neutral
feature.
-7-
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
It is to be noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be considered for limiting
of its scope, for the invention may admit to other equally effective embodiments.
Figure 1 shows an external view of the compact RCBO device according to the
present invention;
Figure 2 shows an internal view of a neutral pole – leakage protection
mechanism;
Figure 3 shows an internal view of a live pole – overload and short-circuit
protection mechanism;
Figure 4 shows load and supply terminals of the neutral pole of the compact
RCBO according to the present invention.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Accordingly the present invention provides a compact two module residual
current circuit breaker with overload protection (RCBO) with a toggle switch
having switched neutral, which is fit able in standard switch and socket outlets. It
can be used for localized over current, short-circuit and leakage fault protection of
appliances.
In general, RCDs (Residual Current Device) can be divided into two categories
based on the technology used:
I. Voltage independent (VI) RCDs, which use the residual current as the
source of energy for operation of the RCD. These are sometimes referred
to as conventional or electromechanical RCDs
II. Voltage dependent (VD) RCDs which use the mains supply voltage as the
source of energy to operate the RCD. These are sometimes referred to as
electronic RCDs.
-8-
RCD is a generic term which includes both RCCBs and RCBOs:
A. RCCB: a residual current circuit breaker without over current sensing.
B. RCBO: a residual current circuit breaker with over current sensing.
An RCCB will open automatically only in response to a residual current. An
RCBO will open automatically in the event of a residual current or an overload or
short-circuit fault.
Referring to the figure 1, figure 2, figure 3 and figure 4, in the present invention,
the mechanism for overload, short-circuit and leakage current protection is
miniaturized and the RCBO is designed in a compact size. The mini RCBO (100)
according to the present invention having a toggle switch (1) for ON/OFF
purpose, a test button mechanism (13) for testing purpose, an indication
mechanism (3) for giving an indication of on/off or trip/non-trip status of the
RCBO so that it can be fitted in standard socket outlets and give the user localized
or additional discriminatory protection at downstream level with easy resetting
and fault detection option. In order to incorporate the mechanism within a small
space constraints, design optimization is done. One of the two modules is
dedicated to a live pole (4) and incorporates means for overcurrent and shortcircuit
fault protection such as incoming and outgoing terminals, a bimetal piece,
an arc chute assembly, a contact assembly, and a solenoid. The second module is
dedicated to a neutral pole (5) and incorporates means for leakage current fault
protection such as the PCB, the solenoid, a current transformer, incoming and
outgoing terminals, a shroud, the test button mechanism, and the indicating
mechanism. A phase wire (6) is brought from the solenoid into the live pole (4),
via a cut in a chassis, to the neutral pole (5) side. The phase wire (6) is passed
through the CT (Current Transformer) (8) and then it is taken back to the live
pole (4) via the same cut in the chassis, wherein the phase wire is welded to the
bimetal piece. An incoming neutral wire (7) also passes through the CT (8) in the
-9-
same direction, both of these forms the primary core of the current transformer
(8). The secondary core of the current transformer (8) provides a signal to the
PCB (9) whenever there is a current leakage, which actuates the solenoid (10)
which in turn trips the device. In case of any fault, a trip bar (11) turns off both
phase and neutral wires (6,7) together thereby disconnecting the downstream
circuits. An indication mechanism (3) gives an indication of on/off or trip/non-trip
status of the RCBO device.
For overcoming the space constraints, the test button mechanism (13) has been
uniquely designed such that there is a direct spring linkage with a metallic pin
(12) on the PCB (9). On pressing a test button (2), the springs short the phase and
neutral internally, to pass a leakage current for testing purpose. The neutral is
switched and its moving contact being longer in size compared to the moving
contact of phase pole to give advance neutral feature. The load and supply
terminals of neutral pole (15, 16) as shown in figure 4 have been brought to the
same side and are staggered with respect to each other, with the shroud (14)
between them giving an electrical clearance. These changes give the space benefit
for incorporating the PCB (9), the current transformer (8), the solenoid (10), the
test button mechanism (13), and other RCD circuitry.
The RCBO (100) is thus useful to protect people against direct contact from live
parts or earth leakage, or from over current and short-circuits faults and is suitable
for use in distribution systems, even at the most downstream circuits. The RCBO
according to the present invention can also be used as an upgrade to provide
additional protection to specific circuits for which leakage protection provision
was not originally provided in the main distribution board. Consider for example
a location where water is present such as washrooms, kitchen and involving risk
of electrocution or fire hazard. The RCBO can be installed in the socket board and
connected in series with appliances such as geyser, washing machine etc. and
other socket outlets which require earth fault protection as well as over
-10-
current/short-circuit protection. This is beneficial because in case of a fault only a
few particular devices downstream of the RCBO, and in the region of fault will be
disconnected in contrast to a wider range of circuits when a prior art switching
device is used for common protection at the distribution board. Moreover this
arrangement will also give the advantage of easy fault detection and easy resetting
to the user. The user would also not need to go to the distribution board, which
may be located farther away, to reset the switching device again and again or
detect faulty circuit which is cumbersome and time-consuming.
Numerous modifications and adaptations of the system 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 true spirit and scope of this invention.

WE CLAIM:
1. A retrofittable twin-module residual circuit breaker device to provide overcurrent,
short-circuit and leakage current protection to one or more interconnected
electrical appliances, characterized in that a first of said twin modules
is dedicated to a live pole and incorporates means for overcurrent and short-circuit
fault protection, and a second of said twin modules is dedicated to a neutral pole
and incorporates means for leakage fault protection, and in that the device is
turned on/off by means of a toggle switch.
2. The device as claimed in claim 1, wherein the means for overcurrent and
short-circuit fault protection consisting of incoming and outgoing terminals, a
bimetal piece, an arc chute assembly, a contact assembly, and a solenoid.
3. The device as claimed in claim 1, wherein the means for leakage fault
protection consisting of a PCB, a solenoid, a current transformer, incoming and
outgoing terminals, a shroud, a test button mechanism, and an indicating
mechanism.
4. The device as claimed in claim 1 wherein the load and supply terminals of the
neutral pole are on the same side and are staggered with respect to each other and
wherein the shroud separating the load and supply terminals.
5. The device as claimed in claim 1 wherein the test button mechanism is
provided with a direct spring linkage with a metallic pin on the PCB and on
pressing a test button, the spring shorts the phase and neutral wires internally, to
pass a leakage current for testing purpose.
6. The device as claimed in claim 1 wherein both the live and neutral poles are switched such that in case of overload/short-circuit or leakage current fault, a trip bar disconnects both the neutral and live pole together thereby protecting the downstream circuits.
7. The device as claimed in claim 1 wherein the moving contact of the switched neutral is longer in size as compared to the moving contact of the phase pole to give an advance neutral feature.