Note: Descriptions are shown in the official language in which they were submitted.
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LOAD CENTER WITH BRANCH-LEVEL CURRENT SENSORS INTEGRATED
INTO POWER BUSES ON A UNIT WITH ON-BOARD CIRCUIT BREAKER
MOUNTS
FIELD OF THE INVENTION
This invention is directed generally to the real-time remote monitoring
of loads powered by a load center, and more particularly to a load center
design that
incorporates power buses, branch-level circuit breaker mounts and pre-breaker,
branch-level current sensors into a single unit.
BACKGROUND OF THE INVENTION
Power lines for an industrial, residential, or commercial building are
provided through an electrical service entrance which is generally connected
to a
load center with a main circuit breaker. After passing through the main
circuit
breaker, the power lines are connected to a bus bar. A bus bar consists of
electrical
conductors (i.e. metal bars), one for each voltage to be distributed to branch
circuits,
with features that allow individual branch circuit breakers to make an
electrical
connection to the bus bar. Several branch circuit breakers are then connected
to a
bus bar to provide power to loads. Circuit breakers are well known in the art.
Examples of circuit breakers are given in U.S. Pat. Nos. 4,553,115; 4,642,726;
4,654,614; 4,887,057; 5,200,724; and 5,341,191. Typically a load center
contains
many branch circuit breakers that can switch power to the loads on the
respective
branch circuits. Loads that are common in location within a building or common
in
their function are typically grouped together on a branch circuit that can be
switched
by a single circuit breaker.
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An energy meter is part of the electrical service entrance to allow for
the electrical service provider to measure kWh for the purposes of billing.
Users of
the electricity are typically billed monthly for the previous month's
electricity use.
However, with the increasing number of electrical appliances and devices in a
household, business, or industrial plant, it is difficult for users to know
what
appliances and devices are large users of electricity, thereby making it
difficult to
know what changes should be made to reduce electricity use. Users interested
in
reducing energy use would benefit from both viewing real-time energy usage,
and
from viewing a more detailed breakdown of energy usage to be able to identify
the
appliances and devices that are the most significant energy users.
An example of a load center where the individual branch circuits are
monitored for the purpose of controlling remotely controllable circuit
breakers is
disclosed in U.S. Pat. No. 5,861,683. In this patent the branch circuits are
monitored
for the purpose of providing information on controlling remotely controllable
circuit
breakers locally using a power line carrier communication method (specifically
the
X10 communication protocol is used). The limitation of the power line carrier
communication method is that the power information cannot be viewed in a
location
= far removed from the building. This means that users cannot view real-
time energy
usage when they are away from the building using the energy. Remote access to
real-time energy information at the branch circuit level would allow users to
monitor
power at any time of day from any location in the world. There is a need,
therefore,
for users to view real-time power or energy usage of individual branch
circuits from a
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remote location, rather than only total building energy usage in time
increments of a
month from a fixed location.
U.S. Pat. No. 5,861,683 suggests the use of current sensors on branch
circuits on the opposite side of the circuit breaker from the main power
connection. A
typical circuit breaker panel consists of a bus bar that distributes power to
individual
branch circuits. The branch circuit breakers have a wire attached connected on
the
opposite side of the circuit breaker from the bus bar connection. This means
that
connecting a current sensor to the opposite side of the circuit breaker from
the bus
bar means that the current sensor must be added in series with a wire, or
around a
wire (depending on the type of current sensor). In either case, this is a
deviation in
the standard installation procedure used for commonly installing branch
circuit
breakers, which can add awkwardness the installation procedure. The side of
the
circuit breakers on which the current sensors are installed does not make a
difference to the function of the current monitoring, however, it does make a
difference to the implementation in terms of size and cost. Embedding the
current
sensor in the bus bar allows for a conventional breaker can be connected to
the bus
bar without any difference in the installation procedure. This would allow for
a lower
cost and more compact solution compared to a current solution where the
current
sensor is on the opposite side of the circuit breaker from the bus bar.
Therefore,
there is need for an improved apparatus for monitoring branch circuit power or
energy by integrating the branch current sensors into the power bus bar to
result in a
compact and low cost method for monitoring power or energy in branch circuits.
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Computerized Electricity Systems Inc., assignee of U.S. Patent
Application Publication No. 2009/0018706, has developed a load center that
employs "smart switches" that are installed in front of conventional branch-
level
breakers to control electricity consumption by branch circuits. The switches
include
current sensors measuring the current through the breakers, and the system
transmits data via the internet to offer remote monitoring possibilities. In
the load
center referenced on the company's website, the control functionality of the
system
results in a module of smart switches that occupies a substantially portion of
the load
center housing, leaving room for only a single-row bank of circuit breakers
mounted
separately from the smart switch module.
The applicant of the present application has developed a unique load
center that incorporates branch circuit current sensing and remote monitoring
functionality in a more compact, simplified design satisfying the needs
identified
above, as well as several others.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a load
center comprising:
a circuit board;
two power buses carried on the circuit board and each arranged for
conductive connection to a respective one of two incoming power lines intended
to
feed the load center;
conductive paths branching away from each power bus in conductive
connection therewith;
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respective branch circuit breaker mounting sites defined on the circuit
board and each conductively linked to a corresponding one of the two power
buses
by a respective one of the conductive paths, each branch circuit breaker
mounting
site being arranged to engagingly receive a branch circuit breaker in a
position
5 placing
said circuit breaker in electrically conductive connection with the respective
conductive path; and
current sensors mounted on the circuit board, each in association with
a respective one of the conductive paths branching off from the power buses to
provide an output responsive to current passing through said respective
conductive
path from the corresponding one of the two power buses to the respective
branch
circuit breaker mounting site.
Preferably a processor is mounted - on the circuit board in
communication with the current sensors to receive current level signals
indicative of
the current passing through the conductive paths.
Preferably a communication interface is located on the circuit board
and linked with the processor to transmit data from the processor to remote
locations
external to the load center.
Preferably the conductive paths comprise conductive branch traces on
the circuit board between the power buses and the branch circuit breaker
mounting
sites.
Preferably the current sensors comprise integrated circuit current
sensors mounted on the circuit board in conductive connection between the
power
buses and the conductive branch traces.
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Each power bus may comprise a respective power bus trace on the
circuit board.
Preferably there is provided a main circuit breaker mounting site on the
circuit board, said main circuit breaker mounting site being arranged to
engagingly
receive a main circuit breaker in a position placing contacts of said circuit
breaker in
electrically conductive connection with the power buses.
Preferably there is provided a voltage sensor arranged to produce
output responsive to a voltage level between the two incoming power lines to
provide voltage level signals indicative of said voltage level to the
processor.
There may be provided multiple layers of conductive traces on the
circuit board within a layout of the power buses and the conductive paths on
said
circuit board. In such instances, the conductive branch traces may include
traces on
opposing sides of the circuit board.
In one embodiment, the branch circuit breaker mounting sites are
arranged in rows comprising two circuit breakers each, the two circuit
breakers of
each row connecting to a same one of the two power buses via branch traces
found
among different layers on the circuit board. In such an embodiment, the branch
circuit breaker mounting sites may all be arranged to engage the branch
circuit
breakers on a same side of the circuit board, the respective conductive path
of one
circuit breaker in each row comprising a conductive trace extending along said
row
on the same side of the circuit board as on which the branch circuit breaker
mounting sites are arranged to engage the branch circuit breakers, and the
respective conductive path of the other circuit breaker in each row comprising
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another conductive trace extending along said row in a different layer of the
circuit
board.
There may be provided a neutral bus carried on the circuit board and
arranged for coupling thereof to an incoming neutral line associated with the
two
incoming power lines, and for connection to the neutral bus of branch circuit
conductors found in branch circuits on sides of branch circuit loads opposite
the
circuit breakers. Likewise a ground bus bar could be provided on the circuit
board,
but alternatively neutral and ground bus bars may be provided elsewhere in the
load
center, for example in the form of conventional neutral and ground bus bars
Mounted on an interior wall of a load center housing or enclosure in a
conventional
manner.
According to a second aspect of the invention there is provided a load
center comprising a housing and, mounted within the housing as a single pre-
fabricated unit of interconnected elements, two power buses, conductive paths
branching away from each power bus in conductive connection therewith,
respective
branch circuit breaker mounting sites each conductively linked to a
corresponding
one of the two power buses by a respective one of the conductive paths, and
current
sensors each association with a respective one of the conductive paths
branching
off from the power buses to provide an output responsive to current passing
through
said respective conductive path between the corresponding one of the two power
buses and the respective branch circuit breaker mounting site.
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Preferably the pre-fabricated unit comprises a carrier mounted to the
housing, and wherein the power buses, conductive paths, branch circuit breaker
mounting sites, and current sensors are all carried on the carrier.
Preferably the carrier comprises a single circuit board on which the
power buses, conductive paths, branch circuit breaker mounting sites, and
current
sensors are all carried.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate a exemplary
embodiments of the present invention:
Figure 1 is a block diagram of a load center of the present invention.
Figure 2 is a schematic illustration of a bus bar layout out of a
conventional load center.
Figure 3 is a schematic illustration of a layout of bus bars and circuit
breaker mounting sites in a single-sided printed circuit board of a first
embodiment
load center of the present invention.
Figure 4 is a schematic illustration demonstrating installation of circuit
breakers in the first embodiment load center layout of Figure 3.
Figures 5A and 5B are schematic illustrations of front and rear sides,
respectively, of a double-sided printed circuit board of a second embodiment
load
center of the present invention.
Figure 6 is a schematic illustration demonstrating installation of circuit
breakers on the front side of the second embodiment load center circuit board
of
Figure 5.
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Figure 7 is a schematic diagram of a front end power supply for a
processor of the load center of the present invention.
Figure 8 is a schematic diagram of a voltage measurement circuit of
the load center of the present invention.
Figure 9 is a schematic diagram of branch circuit current measurement
circuitry of the load center of the present invention.
Figure 10 illustrates input and output voltage waveforms of the voltage
measurement circuit of Figure 8.
DETAILED DESCRIPTION
The present application describes a load center for monitoring the
power or energy of individual loads switched by circuit breakers and
communicating
the power or energy remotely over a communication network, such as the
internet.
The load center includes a housing; a plurality of circuit breakers housed by
the
housing; a power bus bar with integrated current sensors for individual
circuits
housed by the housing; a load center processor housed by the housing; non-
volatile
memory for storing historical power or energy information; and a communication
port
connecting the load center processor to a communication network. The circuit
breakers, which switch a current from the current breaker to the load, are
common
circuit breakers well known in the art that are connected to a bus bar housed
within
the load center housing, which includes integrated current sensors for each
individual circuit switched by a circuit breaker. The current sensor outputs
are
measured by the load center processor, along with the voltage supplied to each
of
the circuits. The load center processor calculates the power or energy for
each
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individual cirauit and communicates this information over a communication
network,
to allow users to remotely view real-time power or energy use of individual
circuits. .
A load center of the present invention allows for remotely monitoring
branch circuit power or energy with current sensors integrated into the power
bus
5 bar. A block diagram of the load center is shown in FIG. 1. The load
center features
a housing (1) that accepts conventional circuit breakers (2), but with the
addition of
an array of current sensors (3), a load center processor (5), and a
communication
interface (6). The current sensors output a voltage relative to the current of
the
branch circuit loads (4). The sensor output voltage is measured by an analog
to
10 digital converter (7) to convert the voltage to a digital value that can
be read by the
load center processor.
Typical residential and commercial buildings feature a 3-wire service
where main power provided from the metered service entrance consists of two
power lines (labeled L1 and L2 in FIG. 1) and a neutral line (labeled N in
FIG. 1). L1
and L2 are connected to a main circuit breaker (8), which then connects each
of
these to the load center bus bar. The illustrated load centers of the present
invention
are designed for use in such typical 3-wire service applications.
The voltage provided to each of the branch circuits through the main
circuit breaker (8) is measured with an isolated voltage measure circuit (9)
that
outputs a voltage relative to the mains voltage, which is interface to the
analog to
digital converter (7). The load center processor reads the digital
representation of
the mains voltage and the digital representation of each of the branch circuit
currents. With this information that load center processor can calculate the
power
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consumption or energy usage of each of the branch circuit loads. This
information
can be transmitted using the communication interface (6) over a communication
network (10) to be viewed by users at remote locations using a common computer
(11) or handheld device (12). The power or energy information can be displayed
to
the user in many different formats. For example, the information can be
displayed
such that a user can view loading profiles over a selected period of time, or,
with the
additional information of the utility electricity rates, the user can
calculate the real-
time costs associated with the power or energy usage of devices on each branch
circuit. This information can be used to improve power efficiency by
determining the
devices that use the largest amount of energy, or the information can be used
to
determine if a branch circuit is too heavily loaded.
A notable difference between this invention and other power
monitoring products are that the current sensors are integrated circuit (IC)
components mounted on a printed wiring board or printed circuit board (PCB)
that
also has the main power bus bars carried or defined thereon. A conventional
circuit
breaker panel has power bus bars that are used to distribute the mains voltage
to
each of the branch circuit breakers. FIG. 2 shows the configuration of a
conventional
load center bus bar. The bus bars consist primarily of two electrically
conductive
pieces (13) (14) each with contact features (15) that allow circuit breakers
to make
an electrical connection to the bus bar on one side of the breaker. The other
side of
the breaker is configured to accept the end of a wire conductor that runs out
to a
load as part of a branch circuit. Voltage is connected to each bus bar through
the
main circuit breaker. In typical North American residential power systems
there is a
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voltage difference between the two conductive pieces or bars of about 240 VAC.
The contact features (15) differ between various load centers according to the
type
of circuit breakers intended to be connected to the bus bar.
The present invention features a bus bar configuration that has
integrated current sensors. FIG. 3 shows one possible implementation of a bus
bar
layout with integrated current sensors. The mains voltage is connected to
large
electrically conductive copper traces (17)(18) on a printed wiring board
through the
main circuit breaker connections (20)(21). The large traces 17, 18 are each of
inverted L-shape with their horizontal legs extending toward one another at
their
upper ends, one leg over the other to position the main breaker connections
20, 21
one over the other in alignment with each other so as to fit the contacts of a
conventional main breaker. Between the vertical legs of the large traces 17,
18,
smaller branch traces 19 extend laterally from adjacent each large trace
toward the
opposing large trace at vertically spaced locations along these large traces.
The
branch traces 19 of each large trace are arranged in exclusive pairs that jut
outwardly away from the large trace in a parallel direction, with one of the
branch
traces 19A of the pair being longer than the other 19B, and also being L-
shaped to
position the distal end of that branch trace past the end of the other branch
trace in
alignment therewith. Moving vertically along the large traces, the pairs of
branch
traces 19 alternate between which of the large traces they extend from.
Adjacent
the distal end of each branch trace, a branch circuit breaker connection 20 is
mounted to the printed wiring board in conductive contact with that branch
trace.
The vertical legs of the longer, wider traces 17, 18 thus cooperate with the
shorter
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narrower traces 19 to resemble a conventional bus bar arrangement of two bus
bars
with vertically running spine or trunk like sections and horizontally jutting
branches,
fingers, legs or stabs, each presenting two connection sites for two breakers
side by
side in a two-breaker row.
The circuit breaker connections (20)(21)(22) are metal components
mounted to the printed circuit board in conductive contact with respective
traces, and
that have features to allow conventional circuit breakers to plug directly
onto the
circuit breaker connections, thereby each making a direct electrical
connection
between the respective bus bar trace and the circuit breakers bus-bar contact.
As
mentioned above, many styles or designs of breaker/busbar contact arrangements
are known in the art, and so different types of breaker contacts may be
employed
within the scope of the present invention to form breaker mounting sites at
which
breakers are receivable in a manner engaging them into conductive connection
with
the branch traces of the busbar layout. In addition to the actual conductive
contact
for establishing electrical connection of the breaker's bus-bar contact with a
respective branch trace, the mounting sites may employ additional retention
features, for example positioned over or laterally outward from the main bus
bar
traces 17, 18, for the circuit breaker housings to clip, snap, hook, screw or
otherwise
fasten onto the board in a position establishing the electrical connection of
the
breaker to the bus bar.
A board mount current sensor (16) is connected between the main
voltage connections (larger traces 17, 18) and each smaller individual printed
wiring
board branch trace (19), which is then connected to branch circuit breaker
through
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the respective circuit breaker contact (22). The current sensors provide a
voltage
output relative to the current through the branch circuits, where the output
voltage is
electrically isolated from the branch circuit voltage. FIG. 4 shows the main
circuit
breaker (23) and several branch circuit breakers (24)(25) installed into
conductive
contact with the bus bar traces having the integrated current sensors from
FIG. 3. In
a conventional manner, the main circuit breaker has screws (26)(27) for the
connection of the mains voltage lines L1 and L2 (as labeled in FIG. 1). The
wire for
the L1 voltage is connected to one screw (26) and the wire for the L2 voltage
is
connected to the other screw (27). Also in a conventional manner, a wire
connecting
to a branch circuit load is connected to a screw (28) on the branch circuit
breaker
(25).
FIG. 5A and FIG. 5B show another possible implementation of a bus
bar with integrated current sensors. In this configuration the printed wiring
board is a
two layer or double sided board where vias 31, 32 are used to connect traces
on one
side of the board to the other. FIG. 5A shows the top side of the printed
wiring board
and FIG. 5B shows the bottom side of the board. Similar to the configuration
of FIG.
3, the mains voltage is connected to large copper traces (29)(30) of inverted
L-shape
on the front side of the printed wiring board for distribution to each of the
branch
circuit breakers connected to smaller branch traces linked to the larger
traces by
current sensors mounted on the board. In this configuration vias (31)(32) in
the
printed wiring board are used to connect a copper trace from one side of the
printed
wiring board to the other with a trace on the back side of the board (33).
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More particularly, unlike the first embodiment where the two branch
traces of each pair are disposed one above the other along the vertical leg of
the
respective larger trace, the two branches 19C, 19D of each pair of traces
defining a
two-breaker row of circuit breaker mounting sites instead initially jut
outward from the
5 larger trace to opposite sides thereof at the same position therealong.
The branch
19C jutting inwardly (i.e. toward the opposing larger trace) consists of a
single trace
extending from the current sensor 16 that connects the branch 19C to the
larger
trace to the respective circuit breaker contact 22. However, the other branch
19D
includes three traces: a first trace 19E jutting outwardly away from the
larger trace
10 on the front of the circuit board, a second trace 19F on the rear side
of the circuit
board running from the outer end of the first trace 19E past the inner end of
the other
branch 19C, and a third trace 19G on the front side of the board running from
the
inner end of the second trace 19F back toward the circuit breaker contact of
the
other branch 19C. A first set of vias 31 connect the first trace 19E to the
second
15 trace 19F, and a second set of vias 32 connect the second trace 19F to
the third
trace 19G.
This way, both branches can occupy the same surface area of the
printed circuit board by using opposing sides thereof to form two different
layers of
conductive tracing. If the branch traces of the circuit board need to be wider
than
the housing thickness of the circuit breakers the contacts 22 are designed to
accommodate, then this configuration has the advantage over the configuration
in
FIG. 3 terms of minimizing space between the circuit breakers of adjacent
rows,
thereby increasing the compactness of the overall collection of installed
branch
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circuit breakers. FIG. 6 shows the main circuit breaker (34) and several
branch
circuit breakers (35)(36) (37) (38) installed in the bus bar with integrated
current
sensors from FIG. 5A.
Low voltage DC supplies are required to power the electronics required
for the load center processor, the AID converter, voltage and current
measuring
interfacing circuitry, and the communication interface. FIG. 7 shows a
possible
implementation of the front end power supply used for the load center
electronics. A
transformer (39) is used for electrical isolation between the low voltage
electronics
power supply and the mains voltage, and to step down the mains voltage to a
lower
voltage that could be input into DC to DC voltage regulators. A full-wave
rectifier (40)
is used on the front end of the power supply, which would be used in
conjunction
with input capacitance to convert the AC voltage output of the transformer to
a DC
voltage. The electronics power supplies (41) would contain several voltage
regulators, that may be switch-mode buck-type voltage regulators or linear
regulators, depending on the current and voltage needs of the electronics.
FIG. 7
shows output voltages of +5 Volts and +3.3 Volts, which are typical voltage
rails
used for electronics, but these may differ on depending on the specific needs
of the
electronics to be powered.
FIG. 8 shows a possible implementation of the voltage measurement
circuit (represented by (9) in FIG. 1). The measured voltage output is
electrically
isolated from the mains voltage with the use of a step-down transformer (42).
The
voltage across L1 and L2 (typically 240 VAC), is stepped-down to a lower
voltage
AC voltage with the use of the transformer (42), and then it is rectified with
=a full-
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wave rectifier (43). The interface circuitry (44) at the output of the full-
wave rectifier
is used to scale the output of the voltage into the measurement range of the
analog
to digital converter. This voltage (labeled Vmeasure in FIG. 8) is then
converted to a
digital representation by the analog to digital converter and read by the load
center
processor. FIG. 10 shows examples of the waveform (51) that would typically be
across L1 and L2, and the resulting waveform (52) at the input to the analog
to
digital converter, where Vmax in FIG. 10 is the maximum voltage that can be
measured by the analog to digital converter. The load center processor samples
the
digital representation of the voltage read by the analog to digital converter
at a
frequency greater than four times the frequency of the AC mains voltage. The
load
center processor can then calculate the voltage across L1 and L2 by applying
the
scaling factors of the transformer (42) and the interface circuitry (44) and
accounting
for the full-wave rectification.
In an alternate embodiment, a neutral bus bar of the load center may
be mounted on circuit board and arranged for connection to the neutral bus of
branch circuit conductors found in branch circuits on sides of branch circuit
loads
opposite the circuit breakers. In such an embodiment, the voltage measurements
may be taken between each hot bus bar and the neutral bar, as opposed to
between
the two hot bus bars (i.e. measuring between L1 and N, and between L2 and N,
instead of between L1 and L2).
The branch circuit current sensors (as shown by (3) in FIG. 1) can be
implemented with several different technologies. Some possibilities are
transformers
that output a small current relative to the output of the branch circuit. This
current
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can then be converted to a voltage with a resistor network. However, the
preferred
solution of the branch circuit current measurement circuitry is shown in FIG.
9. FIG.
9 shows the connection of either L1 or L2 through the main circuit breaker
(45) to the
bus bar (46). The current sensor is implemented with an integrated circuit
that
measures current using the Hall-effect (47), where the strength of magnetic
field
produced by the branch circuit current flow is measured to determine the
magnitude
of the current. An example of a Hall-effect integrated circuit (IC) that could
be used
for the current sensor that is integrated into the bus bar is Allegro
Microsystems part
number ACS712. The Hall-effect current sensor allows the interface circuitry
to be
electrically isolated from the bus bar voltage.
An electrical connection is made through the current sensor to the
branch circuit breaker (50). The interface circuitry internal to the current
sensor (48)
is used create an output voltage that is relative to the current supplied to
the branch
circuit load. The interface circuitry external to the current sensor (49) is
then used to
scale the voltage to appropriate range to be measured by the analog to digital
converter. The load center processor can then calculate the branch circuit
load
current by applying conversion and scaling factors specific to the
implementation of
the interface circuitry. The load center processor samples the digital
representation
of each of the branch circuit current measurements at the same frequency that
is
used to sample the voltage across L1 and L2.
With both the voltage and the branch current measurements, the load
center processor can make calculations to determine a variety of useful
information.
For example, the voltage and current measurements can be used to calculate the
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peak instantaneous voltage, peak instantaneous branch current, and the
difference
in phase of the voltage and current. These can then be used to determine the
average power of the branch circuit load, the power factor of the branch
circuit load,
and the energy used in the load. This information can then be communicated
using
the communication interface to a user in a remote location. The price of
energy can
be included in the calculations, and the user can then see the cost of usage
of
energy in real-time, broken down to the branch circuit level.
The communication interface (6) shown in FIG. 1 can be implemented
with many different types of communication interfaces, one option being an
Ethernet
controller and physical layer interface to allow an Ethernet network cable to
be
connected for communication to the internet. The load center processor can act
as a
web server itself, such that the desired power information can be viewed with
a
commonly available web browsing software, or the load center processor can
pass
the information using a proprietary protocol and use custom software programs
on
the computers and/or handheld devices to display the information.
The processor 5 and communication interface 6 are mounted on the
same circuit board featuring the bus bar main and branch traces, the
integrated
circuit current sensors, the main and branch circuit breaker contacts and the
voltage
measuring circuit, thus providing a self-contained fully-functional assembly
in a
single pre-fabricated unit. Manufacture of a complete load center ready to
install
thus only requires the additional step of mounting this single unit within a
suitably
sized load center housing, which is easily achieved by simply mounting the
circuit
board to the housing interior, since all of the other components are already
mounted,
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carried or otherwise defined on the circuit board itself. Installation of the
load center
is kept simple, requiring only mounting of the housing in a conventional
manner,
installation of commercially available circuit breakers in a conventional
manner,
connection of the incoming power lines in a conventional manner, and
connection of
5 branch circuits to the branch circuit breakers in a conventional manner.
Furthermore, the layout of the various components can be selected to reflect
the
appearance of a conventional load center, as described herein above for the
example of vertically stacked rows of two breakers each, in which the two
breakers
in each row connect to the same bus bar, and adjacent rows connect to opposing
10 bus bars. Thus users or installers of the load center will not be
intimated by an
unfamiliar layout of breakers and connection points.
With a current sensor as the only electronic element between the main
breaker and each branch circuit breaker that provides any function beyond
completion of the electrically conductive path therebetween, branch-circuit
controls
15 or other more complex electronics are avoided, keeping the load center
compact,
easy to manufacture, and cost and material efficient, while still providing
monitoring
capabilities.
While the illustrated embodiments employ printed traces to form the
hot power buses and employ integrated circuit current sensors (current sensor
20 chips), other configurations are also contemplated that would still
benefit from design
as a substantial all-in-one prefabricated unit embodying bus-bars, circuit
breaker
contacts, pre-breaker sensors, and measurement processing devices. For
example,
the main run of the bus bar trace from which the branches or fingers extend
may be
CA 02808735 2013-02-27
21
a piece of bar fixed to the circuit board. The bar may be in conductive
contact with
branch traces incorporating the integrated circuit current sensors, or other
current
sensor types may be employed, for example at a wired connection from the bus
bar
to the respective circuit breaker contact site.
The use of directional terms such as vertical, horizontal, front, rear,
back, upper, lower, top and bottom are used in the above description in the
context
of the orientation in which the load center would typically be mounted in a
conventional manner, i.e. with the housing mounted to a wall in a vertical
orientation
placing a substantially closed rear wall of the housing against the wall, a
front wall of
the housing located at an open side of the housing facing away from the wall,
and
the circuit board mounted in the housing between the front and rear walls to
position
the circuit breakers in side-by-side vertical columns (i.e. vertical stacks of
two-
breaker rows). In a conventional manner, openings in the front wall can be
employed to allow the circuit breaker toggles to be manipulated even with the
front
wall installed/closed to prevent inadvertent contact with live components
inside the
housing, while opening or removal of the front wall provides access to the
interior
components for service, upgrade, inspection, etc. The aforementioned
directional
terms are not intended to limit the present invention to installation in any
particular
orientation or position.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
CA 02808735 2013-02-27
22
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
