Apparatus for Determining Differences Between the Phases of Two Electric Alternating Currents of like Number of Alternations, applicable also to the Regulation of Alternating Current Dynamos.
Year: 1892

page_text: Date of Application, 15th Dec., 1892-Accepted, 22nd Apr., 1893
COMPLETE SPECIFICATION.
Apparatus for Determining Differences Between the Phases of Two
Electric Alternating Currents of like Number of Alternations,
applicable also to the Regulation of Alternating Current Dynamos.
We MICHAEL VOX DOLIVO-DOBROWOLSKY Electrician and the Company
"ALLGEMEINE ELEKTRICITÄTS-GESELLSCHAFT," both of No. 22 Schiffbauer
Damm, Berlin, Prussia 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 present invention relates to an apparatus which allows of the detection and
measurement of any difference that may occur between the phases of two electric
alternating currents of like number of alternations. The said invention also com-
prises a special arrangement whereby the said apparatus will shew and measure any
lag or advance that may have taken place between the phases of the current
furnished by an alternating current dynamo or alternator and those of the electro-
motive force or pressure of this current, and finally an arrangement by means of
which the said apparatus is caused to correct automatically the said difference
between the current and pressure-phases.
In order to make the invention fully understood we first describe the principle
on which it is based, reference being made to the diagram Figure 1.
Supposing a metallic body S. be arranged so that it can be rotated in the
magnetic fields of two conductors or coils, a and b, placed at an angle to each
other. Supposing further each of these coils be fed with an alternating current
and that the two currents have a like number of alternations. As is well known
a rotary movement will be imparted to the body S provided the phases of the
two currents be altered relatively to each other. This principle of producing
rotary movement has already been made use of to construct electric motors. Now,
if simultaneously a counter-force (such for instance as the action of a weight to
be lifted, or of a spring to be wound up, or the attraction of a magnet) be caused
to interfere so as to check the rotation of the said metallic body, the amount of
counterforce absorbed in arresting the rotation and the direction of said force
furnish a means for determining the impulsive momentum or momentum of inertia
produced by those two currents. With a given number of alternations the momentum
of inertia imparted to the metallic body is dependent on the angle formed by the
two inagnetic fields or coils, a and b, on the strength of the two currents, and on the
amount or angle by which their phases are shifted relatively to each other. Under
otherwise similar conditions the said momentum reaches a maximum when the latter
angle is equal to the angle at which the two magnetic fields are set to each other.
In accordance with what is stated above, the apparatus or phase meter consists
principally in the combination, with two stationary coils or sets of coils arranged
at an angle to each other, of a metallic body rotatably placed within the magnetic
fields produced by the said coils, a counteracting device and means for indicating
the angle of oscillation.
Figs. 2 to 7 show diagrammatically ways in which the said phase meter may be
constructed.
In Figure 2 S is a metal disc fixed on a spindle mounted in suitable bearings in
the base-plate of the meter and in the cross bar c which is fixed on the base plate.
F is a spiral spring attached at one end to the spindle and at the other end to the
cross bar c. a, a, and b, b, are two pairs of coils arranged normally so as to surround
the disc S say at right angles to each other. A,,A,, are two binding screws to
which the ends of the coils a, a are connected and B₁, B, are two binding screws to
which the ends of the coils b,b are connected. The spindle of the disc S is provided

page_text: with pointers moving in proximity to scales T. There may however be but one
pointer and one scale.
If one of the two alternating currents to be compared one with another be caused
to flow through the coils a, a, by means of the binding screws A₁, A, and if
simultaneously the other current be permitted to circulate through the coils b, b, by
way of the binding screws B, B2, the disc S will be given a rotative impulse,
provided the phases of one current be shifted relatively to those of the other
current. This rotation will be towards the right or towards the left accordingly
as the phases of one or the other current are in advance of or are lagging behind
those of the other current. The rotation of the disc has the effect of winding up
the spring F. Consequently the rotation will be arrested as soon the tension of
the spring exerts a force equal to that of the rotary impulse, i.e. the momentum of
inertia created by the cooperation of the two currents. When the disc rotates, the
pointers Z rotate with it, and come to a standstill at the time the disc is arrested
by the tension of the spring. The extent of movement made by the pointers is
read off on the scales T. In order, to be independent of the strength of the
currents, the coils, are made moveable so that they can be shifted round the
disc S. In using the apparatus the coils b. b are first shifted until the amplitude
of the pointer Z reaches its maximum by reason of the current in the coils a and b
the angle formed at this moment between the coils a, a and b b being equal to the
angle by which the phases of the two currents are shifted relatively to each other.
This latter angle is indicated on a second scale, T¹, by a pointer Z¹ fixed to the
movable coils.
In many cases this shifting of the coils b, b will not be necessary either because
the two currents are always alike in strength or because it is only required to
determine whether and in what direction a shifting of the phases has taken place.
In such cases the meter may be simplified by fixing both pairs of coils b, b, because
the readings of the scale T are sufficient for the purpose. Such a phasemeter is
represented in Figure 3.
The coils a, a and b may be provided with iron cores to strengthen their effect.
In this case the arrangement can be made in different ways, some of which are
shown in Figures 4, 5, and 6.
According to Figure 4 two groups of coils, a, a and b are wound on a stationary
iron ring M diametrically opposite to each other (as in a Teslamotor). This ring
encompasses another ring, S¹, of iron or other metal, which is mounted on an axis
so as to rotate when acted upon by the currents caused to circulate in the said
coils. In this instance a weight ġ is employed to check the ring S',
In the phase-meter shewn in Figure 5 magnetic attraction is made use of as the
counteracting force. The coils a, a and b are wound on the ends of two iron
cores, M arranged at opposite sides of the moveable disc S, which has attached
to it a piece of iron V, and in proximity of this is arranged a steel magnet N. S.
In the modified arrangement Figure 6 the rotation of the disc is counteracted
by the attraction of an electromagnet M2 having a pole P so arranged as to face
the iron piece V. The coils of this electro magnet are formed by the same
coils, a and b, which are fed with the two currents to be compared with each
other. Thus the said currents simultaneously act to rotate the disc S and to
excite the arresting electro magnet. Such an arrangement possesses the advantage
of making the oscillations of the disc independent of the strength of either
current, as the attractive power of the pole P decreases as the currents diminish
in strength and vice versa.
In the apparatus shewn in Figure 7 the metal body to be rotated consists of a
segment of a ring S2 and is suspended on a spring F¹ so as to form a kind of
pendulum. a and are the two coils which are represented as wound on an iron
core M³ of segmental shape. T is the fixed scale, and Z is a countermark arranged
on the pendulum S2 opposite to the said scale.
A phase-meter organised as described can be used to indicate any difference
arising between the phases of an alternating current and those of the electro-

page_text: motive force or pressure of the same current. For this purpose one coil of the
apparatus has to be wound with wire of such thickness as to be capable of con--
ducting the full current, whilst the other coil has to be composed of a great
number of fine wire windings so that it affords a considerable resistance. The
former coil is inserted in the working circuit and the latter in a shunt from the
said circuit.. Such an arrangement is shown in Figure 8 in which D is the
alternator, E its exciter I. 1' the main or working circuit, R a current consuming
apparatus, P the phase meter and i. i the said shunt. The current circulating
through the latter and consequently through the fine wire wound phase meter coil
has an intensity which is proportional to the electromotive force or pressure at e-
existing between the connecting ends d. d' and a phase that is nearly equal to the
phase of the pressure.
e,
it then
If the working current coincides in phase with its electromotive force
nearly coincides in phase with the pressure measuring current in the shunt i. i¹ and
the phase meter stands at the zero point. If however, according to the nature.
of the consuming apparatus R the working current be caused to lag relatively
to the pressure or to be in advance of the same a like difference will arise between.
the phases of the working current and those of the shunt current and cause the
movable part of the phase meter to oscillate to the right or to the left.
With regard to Figure 9 supposing a number of alternating current generators.
work parallel on the same main circuit, a phase-meter being combined with each
generator in the manner above described. As long as the work of all of the
generators is normal, all of the phase-meters will act in the same manner i.e. they
will depend on the consuming apparatus only. Under "normal" working is to be
understood that each alternator receives as much power as corresponds to the
excitement of the electro magnets, so that the work is done without the
synchronizing power of the alternator intervening. Now experience has shown
that the alternators easily get out of step when their excitement is not in proportion
to the power received. Before however this getting out of step takes place,.
deflections differing in direction are observed in the individual phase-meters, viz.,.
those meters which are combined with generators subjected to stronger excitement
will be seen to oscillate to one side, whilst the meters of those generators which
receive a weaker excitement oscillate to the other side. Thus the various exciting
currents can be corrected according to the indications of the phase meters and
thereby the alternators be prevented from getting out of step.
In order to dispense with necessity for constant observation of the meters, the
arrangement can be made so as to cause each meter to automatically correct the-
excitement of the alternator with which it is used. Such an arrangement is shown
in Figure 10. In this figure P is the phase meter, S the movable part of the
same, G the series of resistance coils for regulating the exciting current and H the
handle by means of which the resistance coils are put into and out of the exciting
circuit. As shown this handle is connected with the movable phase meter part S.
If with this arrangement, any sensible difference takes place between the current
and pressure phases, the part S, in turning to the right or to the left moves the
handle H with it so as to augment or to diminish the number of resistance coils in
the exciting circuit until the proper excitement is restored.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is ;-
1. An apparatus for determining and measuring differences between the phases
of two electric alternating currents of like number of alternations the said apparatus
being composed of two coils or groups of coils set at an angle to each other, a
metallic body rotatably arranged in the magnetic fields of the said coils or groups.
of coils, a device for opposing a counterforce to the rotation of the said metallic body,.
and means for indicating the movements of the latter, one of the two currents being.

page_text: caused to circulate in one coil or group of coils, and the other current being
caused to circulate in the other coil or group of coils, substantially as hereinbefore
described.
2. The combination with the working circuit of an alternator and current con-
suming apparatus connected thereto, of a shunt circuit derived from the two wires
of the working circuit, and a phase meter such as is claimed by the preceding
claiming clause one of the coils or group of coils of the meter being inserted in
the working circuit and the other coil or group of coils in the shunt circuit,
substantially as hereinbefore described.
3. The combination with the working circuit of an alternator and current con-
suming apparatus connected thereto, of a shunt circuit, a phase meter such as is
claimed in the preceding first claiming clause one coil or group of coils of which
phase meter is inserted in the working circuit whilst the other coil or group of
coils is inserted in the shunt circuit, and a counection between the oscillating part
of the meter and the handle for actuating the resistance coils in the exciting
circuit of the alternator substantially as and for the purpose hereinbefore set
forth.
Dated this with day of Dreamboy 1000
J. H. JOHNSON & Co.,
Agents.