FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention:
COMPACT CURRENT TRANSFORMERS AS A POWERING DEVICE
2. Applicant(s):
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400
001, State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to an improved current transformer adapted for measurement and powering purposes. More particularly, the present invention relates to an improved current transformer as powering device adapted to offer relatively flat VA output characteristics so as to satisfy the purpose of supplying power for metering, signal processing, annunciation and operating actuating devices in limited space constraint.
BACKGROUND OF THE INVENTION
Current sensors like Rogowski coils and Hall effect transducers have gained large dominance as a current measurement technique owing to low cost, high reliability, high accuracy and wide measuring range.
The conventional technique of current measurement includes use of iron core current transformers which can be rather bulky and saturate quite early due to use of laminated iron cores. Air core Rogowski coils offer multiple advantages over the existing techniques.
However, such coils are incapable of delivering adequate power output for signal processing, annunciation or operating tripping devices. Also, other electronic sensors like hall effect sensors require auxiliary power. To overcome this disadvantage, Power CTs are used in conjunction with such sensors.
US 5726846 discloses a trip device comprises at least one current transformer for supplying power to electronic circuits. The current transformer comprises a magnetic circuit, surrounding a primary conductor, a secondary winding wound onto a part of the magnetic circuit forming a core, and a magnetic shunt branch connected on the magnetic core. The magnetic shunt comprises an air-gap. When the current flowing in-the primary conductor is of low value, the magnetic flux

stopped by the air-gap flows essentially via the core of the secondary winding. At high current levels the induction is greater and a large part of the magnetic flux passes through the shunt via the air-gap. The current transformer has a non-linear current response which limits excess power supplied to the electronic circuits and dissipated in the transformer. The trip device is useful, for example, in a circuit breaker.
US 6459349 discloses a circuit breaker assembly having an electronic trip unit used to detect an overcurrent condition in a protected electrical circuit. The electronic trip unit being electrically connected to a current transformer used to sense electrical current and provide operating power to the electronic trip unit.
WO 2007/045985 discloses a current transformer (10) comprises a coil (14) , a core (12) and a shunt member (16) . The core forms a magnetic circuit and has a first permeability. At least a portion of the core is encircled by the coil. The shunt member is coupled to the core and has a second permeability. The shunt member is continuous and forms a magnetically parallel path with the at least a portion of the core encircled by the coil . The current transformer may be incorporated in to a trip device.
All above prior art have invented the similar concepts but none of them have incorporated an external component for magnetic flux bypass.
Thus there is a need to provide an improvement in existing technology for drawing power from current flow in an electrical conductor by using an iron core current transformer.
As there exists an upper limit to the power requirement for the various operations, schemes are necessary to limit the power output by either restricting the flux through the iron core or bypassing it away from the secondary coil.

OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.
A basic object of the present invention is to provide an improved current transformer adapted for measurement and powering purposes.
Another object of the present invention is to provide an improved current transformer adapted complete electrical isolation of the sensor from the live conductor.
These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawing:
Fig. 1 illustrates embodiment 1.
Fig, 2 illustrates embodiment 2.
Fig. 3 illustrates embodiment 1 (Side view): Cross sections of bypass limb.
Fig. 4 illustrates embodiment 1 (Side view): Extruded Bypass limb.

Fig. 5 illustrates graph of Modified Power CT versus conventional CT.
SUMMARY OF THE INVENTION
According to one of the embodiment of the present invention there is provided an improved current transformer as powering device, said device comprising
a secondary coil;
a conductor;
an core;
a bypass limb having a flux bypass path substantially adhered to said core and
said limb placed between conductor and secondary coil;
plurality of spacers substantially placed between said bypass limb;
such that said spacers adapted to provide with the air gap in bypass path.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improved current transformer as powering device, said device comprising a secondary coil; a conductor; an core; a bypass limb having a flux bypass path substantially adhered to said core and said limb placed between conductor and secondary coil; plurality of spacers substantially placed between said bypass limb. The spacers adapted to provide with the air gap in bypass path . The bypass path comprises of laminated ferromagnetic preferably iron. The spacer is plastic. The bypass limb is fixed between said conductor and secondary coil. The bypass limb having various shapes and cross section area such as rectangular, circular and like. The bypass limb extrudes out of the plane of said core to enhance the flux bypass feature.
Advantages:
• Compact
• Reliable and consistent power output applicable for AC systems

• Complete electrical isolation of the sensor from the live conductor.
• No temperature rise issues.
• Ease of manufacturability and assembly
Important Features:
• A robust, reliable and accurate power current transformer assembly using precisely positioned flux bypass component for providing power for sensors, metering, signal processing, annunciation and operating electromagnetic actuation mechanisms/other control and communication devices.
• Two potential configurations of assembly in conventional current transformers by placing an external laminated iron piece placed magnetically in parallel to the secondary coil.
• The assemblies placed across a single or multiple current carrying conductors for drawing power from the electrical supply line.
• Variants in dimensions and profile of the bypass component which are possible for retrofitting to obtain same performance characteristics.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the device has been discussed below to describe the way the device operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

According to one of the embodiment (1) of the present invention there is provided as explained in figure 1, a free standing laminated ferromagnetic (preferably iron) flux bypass path is adhered to an existing current transformer core. The bypass limb is held in place using plastic spacers held at each end. The bypass structure is placed between the conductor and secondary coil.
When current passes through the primary conductor, the magnetic field flux generated by the conductor due to current flow links with the laminated iron core and thereby an EMF is induced in the secondary coil owing due Faraday's induction principle. The power delivered by the secondary coil depends on the net iron weight of the core.
As a limited output is only needed in general cases, the output can be clamped by ensuring that the main iron core saturates at a very low operating currents and then the flux is partially diverted to the bypass piece separately connected to the CT.
The scheme not only ensures that output power is clamped effectively after a particular magnitude of current but also the ratings of electronic components which are required for rectification and efficient utilization of derived power get reduced. This scheme presents a very compact technique for drawing operational power in conjunction with a Rogowski coil or any other current sensor.
According to another embodiment (2) of the present invention there is provided as explained in figure 2, an alternate arrangement is proposed along the similar principles. The only difference being that the bypass arrangement is completely external to the current transformer.
Any of the two above proposed embodiments can be used depending on the space available in a given electrical unit or system.

The second system is slightly more advantageous as it would need lesser magnetizing power due to small iron core path in the similar space configurations. However, this method also has a disadvantage that the output would not get absolutely clamped as some part of the flux from the primary conductor can get directly linked to the secondary coil. An external clamping assembly is provided to hold the outer bypass limb in place.
In both the concepts, the spacers decide the air gap in the bypass route and are thereby instrumental in deciding percentage of flux that gets diverted after primary core saturation.
A notable feature of the present invention is that the bypass path is an external component which be easily assembled in an existing current transformer configuration. Also, the concept delivers the flexibility of using other lower permeability materials as any specific design may demand. The structure also offers the advantage of choosing any shape or cross-section as demanded by space constraints (rectangular, circular or any other arbitrary shape). This may be referred in figure 3.
In certain designs, it may also be modified to have the bypass limb extruding out of the plane of main iron core path so as to enhance the flux bypass feature (refer figure 4).

WE CLAIM
1. An improved current transformer as powering device, said device
comprising
a secondary coil;
a conductor;
an core;
a bypass limb having a flux bypass path substantially adhered to said core
and said limb placed between conductor and secondary coil;
plurality of spacers substantially placed between said bypass limb;
such that said spacers adapted to provide with the air gap in bypass path.
2. Device as claimed in claim 1 wherein said bypass path comprises of laminated ferromagnetic preferably iron.
3. Device as claimed in claim 1 wherein said spacer is plastic.
4. Device as claimed in claim 1 wherein said bypass limb is fixed between said conductor and secondary coil.
5. Device as claimed in claim 1 wherein said bypass limb having various shapes and cross section area such as rectangular, circular and like.
6. Device as claimed in claim 5 wherein said bypass limb extrudes out of the plane of said core to enhance the flux bypass feature.
7. An improved current transformer as powering device as herein substantially described and illustrated with the accompanying drawings.