Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE FOR MONITORING CONSUMPTION
OF ELECTRICAL POWER
_ _ , ... . .
The principal object of -the present invell-tion is to
satisfy a need for a convenient and economical device to en-
able users to monitor, and thus gain control over, -the amount
of AC electrical power being consumed by appliances at any
given time.
Without such a monitoring means, the user is apt to
leave the premises with a number of electrical appliances turned
j on, which could or should be turned off during the user's
absence. A safe-ty or fire hazard can sometimes be created
when heav~ current consuming appliances are left unat-tended.
At the present time, no ready economical means is
available for power consumption monitoring without utilizing
¦ relatively expensive instrumentation, including means to
penetrate or otherwise make con-tact with the conductors of
, 15 power supply cables, which is impractical and in some cases
¦ illegal.
j While certain snap-on meters are known in the prior
art-which do not require pene-tration of a cable sheath, these
devices are not operable with the multiple (two and three)
conductor power supply cables presently in wide use.
j The essence of the present invention therefore re-
sides in the provision of a non-penetrating, externally applied
sensing unit particularly constructed to coact with AC power
supply cables, by electromagnetic induction, or as a Hall
j 25 effect sensor. An AC signal from the sensor is converted in
; a 2 volt AC meter which can be read in kilowatt equivalents.
The device is based on the following principles:
(l) The concentric magnetic field around any con-
~¦ ductor is directly proportional to the current flowing in
j 30 the conductor.
(2) Magnetic fields around parallel supply con-
ductors are in opposing relationship, thus creating elliptical
I fields where the major elliptical axes are across the axes
I of the parallel conductors.
. . .
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j (3) Lines of magneti.c flux cutting across a con-
I ductor will induct current flow in that conductor. A similar
i . effect can be obtained by the placement of a Hall effect sensor
¦ in the flux field generated by a conductor.
¦ 5 An object of the invention is to provide a device
I of the above-mentioned -type for monitoring power consumption
in the home or elsewhere which, except for the sensor, can be
~ constructed from commercially available economical components,
¦ thus enabling the manufacturing and sale of -the device at
relatively low cost.
Another object is to provide a device of the mentioned
type which is entirely practical and reliable.
' Other objects and advantages of -the invention will
j become apparent during the course of the following detailed
description in which:
Figure 1 is a plan view of an externally applied
non-penetrating sensing unit in association with a conventional
SE/USE power supply cable, the cable being shown in cross
section;
¦ 20 Figure 2 is a side elevation of the sensing unit:
Figure 3 is a horizontal section taken on line 3-3
of Figure 2 with parts omitted;
Figure 4 is an enlarged cross sectional view of an
~l induction sensor according to the invention applied externally
to the SE/USE cable;
~: Figure 5 is a similar view of a Hall effect sensor
j : applied to the cable;
¦ Figure 6 is a schematic view o~ circuitry involved
j in the device;
Figure 7 is a rragmentary vertical cross section
I taken through the wall of a building on which the invention is
li installed;
Figures 8 and 9 are schematic viaws of other two
and three conductor cables with which the power consumption
monitor can be used; and
. . Figure 10 is a view similar to Figure 1 in cross
J~
section depicting a sensor unit having only a single
magnetically permeable core and electrical sensing element.
The device shown and described herein is a current
measuring device, calibrated for power. As used herein, the
term "power" is employed in the sense that the average
household consumer of electrical power uses and understands the
term.
DETAILED DESCRIPTION ACCORDING T~ THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
.
Referring to the drawings in detail wherein like
numerals designate like parts, an electrical power consumption
monitoring device comprises essentially two main components,
namely a commercial digital voltmeter 10 which can be read in
kilowatt equivalents and a sensor unit 11, Figure 4, or 11',
Figure 5, which can be applied externally to a mul-tiple
conductor power supply cable 12.
Figure 7 shows a typical installation of the
monitoring device, wherein the numeral 13 designates a building
wall on the interior of which is mounted the customary circuit
breaker or fuse box 14. An exteriorly mounted junction box 15
and watt hour meter I6, supplied by the power company, are
connected in the power supply cable 12 which may pass through
the building wall 13 as indicated at 17 for suitable connection
with the box 14. As illustrated, the sensor 11 is mounted
externally on the power supply cable 12 between the meter 16
and the point where the cable enters the building. It should
be unserstood, however, that the sensor can be applied to the
cable 12 at any convenien-t point outside or inside of the
building where the cable is exposed, and in this sense the
invention is not limited to the particular arrangement shown in
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Figure 7. The power consumption indicating meter 10 is
installed at any convenient location within the building9 as on
the wall 13, or elsewhere is preferred.
It should also be understood that in some cases the
invention including the sensor 11 and meter or read-out device
10 may be completely portable, whereby a user can apply the
sensor 11 to the cable 12 at any point while reading the
portable meter. Furthermore, the sensor 11 of the portable
unit may be integrated with the meter in some cases to monitor
any AC power consuming device having a two or three conductor
power supply cable.
; The illustrated cable 12, typically a SE/USE power
supply cable commonly in wide usage, comprises two side-by-side
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parallel conductors 18 surrounded by spirally wrapped shield-
ing conductors 19 which carry the neutral or imbalanced re-
mainder of the current. In this invention, the imbalance is
negated ~rom the high supply side ancl added to the low supply
5 side in terms of flux induced voltage. The cable 12 which has
a suitable insulating sheath is generally elliptical in cross
section. The invention may also be used with non-shielded
two and three conductor cables 12a and 12b of the types illus-
trated in Figures 8 and 9. To allow ma~imum readings on -the
1~ meter 10, the cables 12a and 12b should be oriented relative
to the sensor 11, as shown in Figures 8 and 9.
The heart of the invention resides in the induction
or Hall effect sensor 11 or 11'. ~he sensor 11, which utilizes
the induction effect in its operation, comprises two identical
15 opposing laminated iron cores 20 placed 180~ apart in the
plane common to the parallel conductors 18. Each iron core is
wrapped with a multi-turn coil 21 of conducting wire and each
iron core with its coil is encapsulated in epoxy 22 or equival-
ent non-conducting and non-magnetic material. The epoxy
20 encapsulation is recessed as at 23 to snugly engage the oppo-
site sides of the cable 12 when the sensor is applied thereto.
Bosses 24 are molded on the encapsulating material and these
bosses have aligned openings 25 receiving a clamping bolt 26
carrying a winged nut 27, whereby the two cores 20 and their
25 encapsulated coils 21 can be clampingly engaged with opposite
sides of the cable 12 without any penetration of -the cable
sheath and without establishing a physical connection with the
two conductor branches 18.
As shown in Figure 6, the two induction coils 21 are
30 electrically connected in series aiding relationship, whereby
the total voltage signal produced by the coils is sent to the
meter or read-out device 10.
Additionally, as shown in Figure 6, 12~ volts AC
is applied through on-off switch 28 -to transformer 29. A
35 conventional center tapped full wave rectifier using diodes
30 and 31 provides pulsating DC ts) filter capacitor 32 and 5
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volt regulator 33. Regulated 5 volts DC is supplied to DC
meter 10. Resistor 34 is used to limit dissipation in regulator
33 and provides surge protection for diodes 30 and 31.
Diodes 35 and 36 are connected as conventional half
wave rectifiers for positive and negative voltage output and
capacitors 37 and 38 are filter capacitors. Resistance 39
and diode 40 form a conventional zener regulator circui-t for
~15 volts DC regulator 33, and resistor 41 and diode 42 form a
similar regulator circuit for -15 volts DC.
1~ The +15 volts supplies provide operating voltages
for integrated circuit module 43, an operational amplifier
working in conjunction with associated components to provide
RMS to DC conversion in the converter circuit 44. Potentio-
meter 45 is for calibration adjustment.
Due to the elliptical fields of flux generated around
parallel conductors 18, Figure 4, the two iron cores 20 collect
and channel the bulk of the magnetic flux through the cores,
which induces an AC voltage in the two coils 21 in direct
proportion to the current flowing in the parallel conductors
20 18, the coils 21 being connected in series aiding relationship.
This voltage is delivered to the converter 44, as described.
~; In an alternate embodiment of the invention shown
in Figure 5, the sensor 11' is a Hall efect sensor instead of
; an induction sensor and the induction coils 21 are omitted.
- 25 In lieu thereof, two laminated iron cores 46 are placed rela-
tive to the cable assembly 12 in the same manner previously
described, namely, 180 apart in a plane passing through the
axes of the two parallel cable conductors 18. Two Hall effect
devices 47 are placed within gaps of the two iron cores 46
30 with their output terminals connected to the wires 48 and 49,
Figure 6. The system operates with the Hall effect devices
in the identical manner that it operates with the two induction
coils, with relation to the cable assembly 12. The Hall
effect devices 47 are of a type manufactured by Ohio Semi-
35 tronics, Inc., 1205 Chesapeake Ave., Columbus, Ohio 43212,Model No. HP 316 or equivalent devices.
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In either embodiment of the invention, it is only
necessary to apply the sensor 11 or 11' externally to the cable
assembly 12, as shown in the drawings, and to close the switch
28 to activate the power supply. The AC signal from the sensor
11 or 11' is instantly converted to a DC signal in the RMS
to DC converter 44, which signal is read in kilowatt equival-
ents on the DC meter 10.
As shown in Figure 10, it is not essential to the
operation of the system to provide two opposing magnetically
permeable cores each having an induction coil or Hall effec-t
element, as previously describe~. Instead, Figure 1~, the power
cable attached sensor unit 50 may include a single magnetically
permeable (iron) core 51 whose particular shape is not critical.
A single induction coil 52 is wound on the core 51, as shown.
In some cases, a Hall effect sensor, as disclosed in Figure 5,
may be used, in which case only a single core element 46 and
Hall effect device ~7 is utiiize~.
With continued reference to Figure 10, the single
core element 51 and coil 52 are encased in epoxy 53 shaped to
provide a boss 5~ having a bolt receiving aperture 55.
For securing the sensor unit 50 to the power cable
12 where only a single core 51 is utilized, an opposing blank
block 56 formed of epoxy or sturdy plastics material having
the same shape as the core and coil containing element is pro-
vided. The block 56 contains no electromagnetic components.
The block 56 has an aperture 57 to register with the opposing
aperture 55 and receive a bolt 58 serving to secure the single
core sensor unit 50 in assembled relationship with the power
cable 12.
The same arrangement is employed if the sensor unit
is of the Hall effect type, shown in Figure 5. In this case,
only one magnetically permeable core is utilized and the oppos-
ing unit on the other side of the power cable is a blank block
serving only to complete the attachment of the sensing unit
clampingly to the exterior of the power supply cable 12 without
penetrating the latter.
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The mode o~ operation of the device constructed with
either one or two magnetically permeable cores and associated
induction coil or coils or Hall effect element or elements is
essentially as described. The circuitry shown in Figure 6 for
a dual core and coil embodiment is also basically unchanged
by the elimination of one core and coil.
The present invention can be utilized in single phase
or three phase AC power systems or in DC power systems, withou-t
any significant change in the circuitry of Figure 6.
A home owner or other user of the invention, by
observing the meter 10, can readily determine at any time whether
normal power consumption or excessive consumption is occurring.
A normal reading on the meter 10 might be reflected by the
numeral 2 or 3, while an excessive reading would be anything
above 2 or 3. If excessive power consumption is occurring,
corrective steps can be taken as by shutting of F or turning
down high energy consuming appliances. The device can indicate
~power consumption of individual appliances or entire household
power consumption.
