Energy Meters for Alternating Currents.
Year: 1898

page_text: Date of Application, 2nd July, 1898-Accepted, 7th Jan., 1899
COMPLETE SPECIFICATION.
Electric Energy Meters for Alternating Currents.
We, FRITZ LAARMANN, Engineer, and HERMANN BROCKELT, Electrician, both of
14, Werderstrasse, Dresden, in the Empire of Germany, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The object of this invention is to provide an electricity meter for alternating
currents, the purpose of which is to measure the amount of work done in a current
curcuit, during any desired time, or, in other words to indicate the number of
rotations made by a rotary body in such time.
This meter is composed substantially of a metallic rotary body which is exposed
to the action of three magnetic fields with displacement or shifting of phase in
relation to one another, or of three groups of such fields, the phase shifting or dis-
placement being effected as follows:-The first field or first group of fields is
produced by the main current, the second field or second group of fields by means
of a solenoid of very considerable self induction, and which branches off from two
points of the current circuit, between which the work made use of is to be measured,
whilst the third field or a third group of fields is produced by the induction of the
second field. The magnetic fields however contrary to the known arrangement of
Ferraris do not cross in the rotary body, but pass through different parts thereof
independently of one another.
Figs. 1 and 2 represent a simple form of the meter with three magnetic fields.
The rotary body which is exposed to the action of the three fields b c d having
displacement or shifting of phase in relation to one another has in this instance the
form of a disc f which may be made of any desired metal, as copper, iron, brass,
aluminium, German silver or the like. If the winding of the electromagnet 6 be
introduced into the main current circuits; the primary winding n of the electro-
magnet c into the shunt current-circuit, and the secondary winding o be connected
with the electromagnet d (see Fig. 3 in which a indicates a source of alternating
current, and e current consumers in parallel); the disc f is set in rotation. The
direction of rotation is determined by the manner in which the two electro-
magnets b and c are put into circuit; if this be done so that both have apparently
the same polarity, the direction of the lines of force is the same in both without
shifting of the phases; and the rotation is effected from the electromagnet b of the
main current circuit to the electromagnet c of the shunt current circuit. If the
electromagnets b and c be put into circuit in a contrary manner (dissimilar polarity)
the direction of rotation will also be contrary in relation to the first.
Instead of employing the whole of the principal or of the shunt current for
exciting the field b c D, a portion only may be utilised, in the manner known, with
the assistance of eligible resistances, and a proportional excitation of the fields b cd,
can be effectively obtained by the transforming of the principal or of the shunt
current.
The number of rotations will be indicated on a suitable indicating mechanism.
The explanation of this rotation is as follows: In consequence of the alternation
of the exciting currents in the disc f the electromagnets b as well as the

page_text: electromagnet & produce eddy currents (also known as Foucoult currents). The
course of the middle lines of this eddy current in the rotary body is indicated in
Figs. 4 and 5 by punctured curves p p¹ p2. If now the inductive resistance of the
primary shunt circuit winding n of the electromagnet c is very great in proportion to
the Ohmic resistance, the magnetic phase of the same is shifted in relation to that of
the main current electromagnet b to the extent of one fourth the length of the curve
(90 degrees), as shown in Figs. 6 and 7 in which k represents the magnetic curve of
the principal current, that of the shunt current and 2 that of the induced
consequently induction or auxiliary field. Fig. 6 illustrates the case in which the
electromagnets b c d possess apparently similar polarity. In this case in consequence
of inductive origin-the phase of the shunt current magnet c in relation to that of
the principal current magnet b and the phase of the auxiliary electro-magnet d in
relation to that of its producer-the shunt circuit magnet c is kept back;
consequently the phase of the eddy currents (Foucoult currents) produced in the
disc f by the shunt current magnet c is also kept back in relation to the eddy
currents induced by the principal current electromagnet b, and the eddy currents (2
produced in the disc f by the auxiliary field magnet dare again kept back in
relation or in opposition to the eddy currents of the shunt circuit magnet c, to
the extent of one fourth of the length of the curve, that is to say, if the eddy
currents of the one order (synonymous or equivalent for the electro-magnets b cd)
are at the positive maximum of their strength the others are at nil and opposite
(negative maximum). The eddy currents are indicated by wavy lines ¹ in Figs. 6
and 7.
6:
l
The maximum of the eddy currents (1 12 however fall together with those of the
magnetisings "kk¹² as shown in Fig. 6 and in fact so that the eddy currents/
are constantly drawn towards the shunt current magnet c (see Fig. 4-the arrow u)
and the eddy currents of the shunt current magnet c constantly repelled by the
principal current magnet b (Fig. 4-arrow u) whilst the eddy currents produced
by the auxiliary field dare repelled by the shunt current magnet c and the eddy
currents of the shunt current magnet c constantly drawn towards the
auxiliary electromagnet d (Fig. 4-arrow t) that is to say the rotation of the disc is
positively in the direction from the principal magnet 6 towards the shunt current
magnet c whilst the braking of the disc f is effected in an opposite sense to the
direction of rotation; therefore the direction of motion from the auxiliary field
electromagnet to the principal current electromagnet b, is positive and continuous.
Fig. 7 represents the case in which the electromagnets b c d are put in circuit with
apparently opposite polarity. From this figure it will be seen that the eddy
currents of the principal current electromagnet b are repelled from the shunt
current electromagnet c and the eddy currents of the shunt current electromagnet c
drawn towards the principal current electromagnet whilst this time also the
braking eddy currents 12 of the auxiliary field dare repelled from the shunt current
electromagnet c, and the eddy currents of the shunt current electromagnet c
drawn towards the auxiliary field electromagnet. The direction of motion of the
rotary body is therefore as shown by the arrow r in Fig. 5 and the direction of the
braking eddy currents is shown by the arrows in Fig. 5.
As
The rotation of the disc f through the three electromagnetic fields b c d again
produces in the disc f itself eddy currents, the course of which is to be seen from
Figs. 8, 9 and 10. These eddy currents m m¹ m² effect the braking of the disc
precisely as those eddy currents produced by the auxiliary field magnet d.
for the production of the eddy currents m m¹ and m² a certain working capacity or
energy is required which is obtained or taken from the attraction aud repulsion of
the electromagnets b c d acting on the eddy currents 112 produced by them. The
number of rotations of the rotary body will be so regulated as to express the
difference between each pair of forces, that of motion and that of braking, or
in other words, the number of rotations of the disc f will always be so adjusted
that the expenditure of work or energy will be equal to the working power o
work done.

page_text: As already mentioned, instead of three simple fields two groups each comprising
three fields may be caused to act on the rotary body f. Fig. 11 shows by way of
example an arrangement with two principal current electromagnets 661, two shunt
current electromagnets e e¹ and two anxiliary field electromagnets d d¹.
It may here be pointed out that, in order that the attracting and repelling actions
of the electromagnets 6 61 c c and d d¹ or the eddy currents thereby produced in
the rotary body, may be added together, the magnets (for example 6 and 6') belonging
to the same group must be connected or put in circuit with different polarity.
The manner of exciting the auxiliary field electromagnet d can be effected in
various ways without prejudice to what is essential in this meter. For instance in
Figs. 12 and 13 the secondary winding o o' of the electromagnet c is arranged on
the closing piece or terminal of the same. Fig. 14 shows a similar arrangement,
only that, in this case, the secondary winding o of the electromagnet c is transplaced
to one arm v of the same.
The outward form of the magnetic fields as well as their arrangement in relation
to one another is left entirely to the object of the constructor. In any case, however,
the magnetic fields bed must be independent of each other and must in no case be
connected (or equivalent) by means of magnetic metal. The magnetic fields should
not cross in any case or run mutually in any of their parts.
Instead of the auxiliary field, the current generated in the secondary solenoid o
may act on any other selected braking body that may be rigidly connected with the
rotary body 8. Fig. 15 shows an arrangement of the meter from this point of view,
in which the third field d is replaced by a metallic hollow cylinder placed in the
interior of a solenoid i. For diminishing the magnetic resistance, pieces of
magnetic iron may be placed inside the hollow cylinder.
The pieces of iron can be arranged firmly and immoveably, which would be
preferable, they can nevertheless rotate with the rotary body, thus are connected
with the same.
The action of the apparatus is exactly like that of the one previously described.
The actuating and braking eddy currents circulate in this case in the covering
surfaces of the hollow cylinder.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that we
claim is-
1. In an electricity meter for alternating currents, the arrangement of three
un-connected and independent magnetic fields, with shifting or displacement of phase
in relation to one another, of which fields one field is excited by the principal
current or a current proportional thereto, the second field c by the shunt current or
a current proportional thereto, whilst the third field d is produced by the induced
current of the field c in such a manner that the fields b c d act inductively and
dynamically on a metallic rotary body.
2. In an electricity meter as in Claim 1, the arrangement of several groups of
the fields b c d which act on one or more rotary bodies exactly as stated in
Claim 1.
3. In an electricity meter the replacing of the field or fields d by one or more
hollow cylinders rotating in the interior of a solenoid (Fig. 15) induced by the
field c in such a manner that this solenoid acts inductively and dynamically on the
cylinder h.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.