FIELD OF INVENTION
The present invention relates to a method and an enhanced local control box for
generating inbuilt power supply in the local control box to operate power
contactors and indication lamps in heating panels of ESP hoppers.
BACKGROUND OF INVENTION
Electrostatic precipitation is one of the most effective technology to control air
pollution generated by industrial emissions. This technique, highly effective in
controlling air pollution, is used for removal of undesirable particulate matter
from a gas stream by electrostatic precipitation. Electrostatic precipitator
(hereinafter referred to as ESP) is an air pollution control device designed to
electrically charge and collect particulates generated from industrial processes
such as those occurring in power plants, cement plants, pulp and paper mills and
utilities etc. The electrically charged particles are attracted towards electrode
plates, viz. discharge electrode and collection plate. ESP is divided into a plurality
of fields depending on the dust load. During the operation of an electrostatic
precipitator, the dust from collector plates, and discharge electrodes must be
periodically removed for further conveying of the collected dust and to ensure
effective precipitation of dust.
The dust collected/deposited on the collecting electrodes and discharge
electrodes are removed using rapping mechanism, and is collected in the
hoppers. This collected dust is periodically removed (approximately at the
interval of 8 hours) from the hopper using ash handling system. Between this
interval of 8 hours, the collected dust is retained in the hoppers. During this
period, the dust temperature has to be maintained above acid dew point

(90 deg.C) to avoid solidification of ash and ensure free flow of dust during
removal. For maintaining this surface temperature uniformly throughout l/3rd of
hopper wall surface, panel type heaters are used. The panel type of heaters are
controlled from local junction box. Further, for saving power during stabilized
operation of the boiler, 50% of hopper heaters are normally switched off using a
half curtain arrangement. This half curtain switching is achieved at the local
control box using power contactors.
According to prior art, the local junction box requires separate control supply for
controlling the auxiliary power contactors. For this purpose, separate control
supply is taken from the Auxiliary control panel to a distribution junction box.
From the distribution junction box, this control supply is distributed to around 40
nos. of local junction box for a 500 MW boiler. This involves a lot of cabling
between Auxiliary control panel and the local junction box plus a distribution
junction box in between Auxiliary control panel and a local junction box.
OBJECTS OF THE INVENTION
It is therefore an object of invention is to propose an enhanced local junction
box enabled to generate inbuilt power supply to operate power contractors and
indication lamps in heating panels of boilers, which eliminates the external
control supply, cables for external control supply and distribution junction.
Another object of the invention is to propose an enhanced local junction box
enabled to generate inbuilt control supply to operate power contractors and
indication lamps, in heating panels of boilers, which simplifies the erection work
and ease out the process of troubleshooting.

A further object of the invention is to propose a method for generating in-built
power supply in the local control box to operate power contractors and indication
lamps in the heating panels of boilers.
SUMMARY OF THE INVENTION
The purpose of the invented device is for distribution of 415 volt power supply to
the panel type hopper heaters. Half curtain is provided for the hopper heaters,
which enables switching OFF 50% of the hopper heaters during stabilized
operation of boiler. This is done by controlling the contactors of 50% of the
hopper heaters. For controlling this contactors, 110V control supply is generated
using step down transformers from the main 415V powers supply.
The present invention enables generation of a control supply from the main
supply within the local control box by using step-down transformers. This control
supply will be used to control the auxiliary contactors in the local control box.
Based on requirement a single or dual transformer is provided to generate the
local control supply. In dual transformer system, at least two nos. of the
transformers will be used for redundancy purpose.
The inventive method avoids external control supply, accessories like control
cables, selector switches and control distribution junction box, thereby increasing
the reliability and simplifying the erection and trouble shooting.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is hardware block diagram of the invented enhanced Local control box.

Figure 1 - Schematically illustrates the difference between the prior art and
invention.
DETAILD DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The hardware block diagram of the invented enhanced Local control box for
controlling the auxiliary contactors is shown in figure 1.
In the hardware block diagram, blocks (CSTl) and (CST2) is the control supply
transformer used to generate the 110 Volt local control supply. This control
supply is used to control the block (POWER CONTACTOR K) which is feeding the
415V power supply to the heaters.
Figure 2 shows the differences in the prior art method and the inventive method
as well as the differences between the prior art LCB and the LCB modified
according to the invention.
In the prior art method, block DPSW is used for selecting any one of the two
control supplies for redundancy purpose. The block CJBOX is used for distributing
the control supply to all the LCB's. The block 3C-2.5 is the cables used for
distributing the power supply from CJBOX to all the LCB's.
In the new method with modified LCB shown, all these blocks (DPSW), (CJBOX)
and (3C-2.5) are eliminated without affecting the existing performance.

According to the invention, the local power supply is generated in the control box
itself thereby avoiding external power supply and cables for external
powersupply. The local control box as modified according to the invention is used
for controlling the hopper heaters of the electrostatic precipitator. The local
junction box of the invention is provided with a glowing 'LED' to indicate error in
case of any faults.

WE CLAIM :
1. A method for generating in-built power supply in the local control box
to operate power contactors and indication lamps without adapting
external power supply from distribution junction box in an ash-
handling system of a boiler equipped with electrostatic precipitator, the
method comprising the steps of:
- providing at least two control supply transformers in the local control box
which are enabled to step down the main power supply of 415V to 110V,
control the auxiliary power contactors, and switch off the pre-determined
number of hopper heaters of the ash-handling system during stabilized
operation of the boiler.
2. A method for generating in-built power supply in the local control box
to operate power contactors and indication lamps in an ash-handling
system of a boiler equipped with electrostatic precipitator as
substantially described and illustrated herein with reference to the
accompanying drawings.

The invention relates to a method for generating in-built power supply in the
local control box to operate power contactors and indication lamps without
adapting external power supply from distribution junction box in an ash-handling
system of a boiler equipped with electrostatic precipitator, the
method comprising the steps of : providing at least two control supply
transformers in the local control box which are enabled to step down the
main power supply of 415V to 110V, control the auxiliary power contactors,
and switch off the pre-determined number of hopper heaters of the ash-handling
system during stabilized operation of the boiler.