Method and Apparatus for Dividing, an Alternating Current into Two Currents, whose phases, are shifted, relatively to each other, more particularly applicable for. Working or Starting single phase alternate Current Motors
Year: 1897

page_text: Date of Application, 30th Jan., 1897
Complete Specification Left, 29th Oct.,
1897-Accepted,
11th Dec.,
1897
PROVISIONAL SPECIFICATION.
n°
34
"Method and Apparatus for Dividing, an Alternating Current into
Two Currents, whose phases, are shifted, relatively to each
other, more particularly applicable for. Working or Starting
single phase alternate Current Motors."
: 4
'est
We, SIEMENS BROTHERS & Co., LIMITED, of 12 Queen Anne's Gate, Westminster
in the County, of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Siemens and, Halske,
of 94 Markgrafenstrasse, Berlin, in the German Empire, Electrical Engineers) to be
as follows:-
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3. k
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f.
This invention relates to a method according to which, by the division of a single
alternating current two alternating currents of differing phase are obtained, which
can then be used in combination for producing a rotary electro-magnetic field... -
.. According to this method, every desired shifting of the phases between the two
currents, can be obtained; in particular it,, is suitable for producing two currents
whose phases are shifted, by, 90°. The rotary electromagnetic field produced by
these currents therefore enables for example, single phase alternate current motors
to be started with considerable power.
convenient method of producing a phase shift of 90° between the currents
producing a rotary field is of particular value, if the rotary field is to be, employed to
actuate the pointers of a measuring instrument, or to drive an armature the speed of
rotation of which is, required to., represent the measure of the electrical energy
consumed, because with these instruments it is. necessary that the two currents shall
have their phases shifted accurately 90°, from each other.,,,
[
For explaining the above statement we will, refer to Figures, 14 and 1 of the
accompanying drawing which shew the known diagram of a Ferraris rotary
phase current motor. AA is an. iron ring, built up of, sheet metal, and intermediate
layers of insulating material and having,, four polar extensions B, В ВВ
surrounding a similarly, constructed iron core E. Between the polar, extensions and
the core E is an air space in which is introduced a cylinder F of conducting material
such as sheet copper, which, can rotate freely on the axis. G. On the polar
extensions B, B₁ are fitted two windings C C of thick wire which are connected
either in parallel, or, in series; on, the, polar extensions B2, B₁ are fitted two
windings D..D of thin wire which are, similarly connected. If an alternating
current I, passes through the windings C C, and an alternating current I, through
the windings D D and if their phases are shifted to the extent, then the turning
moment exercised on the stationary drum F will be equal to
.

page_text: K = C I, I, sin = C₁ I₁ E₁ cos ₁
if, represents the phase-shift between I, and E₁.
The turning moment of the drum F F in this case indicates the work I, E₁ cos p.
The drum may be provided with a spiral spring which imparts to it a certain
position of rest and which in every position holds a certain turning moment in
equilibrio so that the position of the drum constitutes a measure for the work. A
measuring instrument is thus obtained which indicates the work of an alternating
current, or, if the pressure E₁ be regarded as constant, the working component of the
strength of current namely I₁ cos ₁. The drum can however also be made to revolve
and be connected with a counter, for employing the instrument, when combined
with a suitable braking arrangement, directly as a Watt-hour meter.
Such arrangements are well known, as are also others in which for instance the
cylinder is replaced by a circular disc, and they are only mentioned here for pointing
out that with such instruments the necessary condition for correct working consists
in that the current I, shall be proportional to the pressure E, and that both shall be
shifted as regards their phase by exactly 90°.
The present invention has for its object an arrangement which enables a
phase-shift of exactly 90° to be established between I, and E. The extent of
the phase-shift between I, and E, will, with a certain arrangement, be dependent
upon the current curve of the current that is to be measured. The arrangement
hereinafter described enables also this phase-shift to be adjusted to 90° without
much difficulty for different current curves.
The arrangement according to this invention is shewn diagrammatically at
Figure 2.
The means for effecting a phase shift of 90° between the current I2 and the
pressure E₁ consists in introducing the windings D D in the bridge wire of a
Wheatstone bridge. The bus bars S, and S, are assumed to be connected to the
source of current, and from these the working current is taken for feeding the
lamps K or motors I. The two terminals P and Q are connected to the bus
bars S₁, S.
Between P and are introduced two parallel branches P. M. Q. and P N Q, of
which the opposite sides P M and Q N have a large self induction with small
resistance while the sides P N and Q M have each a considerable resistance with
small self induction. Under these circumstances a considerable pressure will exist
between M and N and this pressure has a phase shift relatively to the pressure
between P and Q, that is to say, relatively to the working pressure which may be
of any extent.
Such phase-shift can be made smaller or greater than 90° according to the
choice of the resistances and the self-induction co-efficients R and L in the
branches P M Q and P N Q. If there is no current in the bridge branch M N,
the condition may be easily established for giving the pressure between M and N a
90° phase shift relatively to the pressure between P and Q.
If the sides P N and Q M have no self-induction and an equal resistance R₁ and
if the sides P M and Q. N have equal resistances R, and an equal self-induction
co-efficient L (Figure 3), then with a sine current the condition for the phase shift
of 90° is:-

page_text: of the bridge need not be great and the entire apparatus requires no considerable
expenditure of electric energy.
The equality of the self induction co-efficients and resistances in opposite branches
of the bridge was only assumed for the sake of simplicity.
The object aimed at can also be attained if for instance the branch P. N. Q has no
self-induction. Capacity can also be substituted for ohmic resistance. The condition
that the current flowing between M and N shall have a phase shift of 90° relatively
to the pressure between P and Q can be fulfilled in various ways.
.
It is furthermore not necessary that for the production of the two self-induction
co-efficients two different apparatus should be employed; two coils can be used which
are wound one over the other and have a common iron core.
The adjustment of the phase shift is effected in a simple manner, by varying
either the self-induction or the resistance in one or both branches P MQ and P N Q.
For this purpose the one coil of a sensitive dynamometer, which with resistance in
series shall have exactly the same resistance and the same self induction as the coils D D
with the resistance W in series with them, can be introduced between M and N,
while through the other coil a current is sent which has the same phase as the
working pressure.
The dynamometer will swing to the one side or the other according as the angle
of the phase shift is greater or smaller than 90°, and it will remain in the middle
position if the angle is exactly 90°, so that it will be seen that the desired phase-shift
of 90° can by this means be accurately and readily adjusted.
An arrangement for working or for starting single phase current motors is shown
at Figure 4. CC is the winding through which the current flows continuously and
which is connected up by the switches A, A,. D D is the auxiliary winding which
produces a second magnetic field, whose axis with a bi-polar motor such as shewn, is
situated at right angles to the axis of the field produced by C. C.
The winding D D as a rule only receives current for starting, and can therefore he
cut out by the switches A, and A. This auxiliary winding is connected up as bridge
of the bridge connection between M and N.
As electromotive forces will appear in the auxiliary winding D D when the motor
is running a cutting out switch A must be provided in order that when the switch A
is open, currents may not appear in the bridge. Experiments shew that with this
arrangement a very powerful torque can be obtained at starting.
Dated this 30th day of January 1897.
ABEL & IMRAY
Agents for the Applicants.
"Method and Apparatus for Dividing an Alternating Current into
Two Currents, whose phases are shifted relatively to each
other, more particularly applicable for Working or Starting
single phase alternate Current Motors."
We, SIEMENS BROTHERS & Co. LIMITED, of 12 Queen Anne's Gate, Westminster, in
the County of London, Electrical Engineers, do hereby declare the nature of this in-
vention (which has been communicated to us from abroad by Siemens & Halske of
94 Markgrafenstrasse, Berlin, in the German Empire, Electrical Engineers) and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement:-
This invention relates to a method according to which, by the division of a single

page_text: alternating current two alternating currents of differing phase are obtained, which
can then be used in combination for producing a rotary electro-magnetic field.
f
According to this method every desired shifting of the phases between the two
currents can be obtained, in particular it is suitable for producing two currents whose
phases are shifted by 90°. The rotary electro-magnetic field produced by these cur-
rents therefore enables for example, single phase alternate current motors to be
started with considerable power.
A convenient method of producing a phase shift of 90° between the currents pro-
ducing a rotary field is of particular value if the rotary field is to be employed to
actuate the pointers of a measuring instrument, or to drive an armature the speed of
rotation of which is required to represent the measure of the electrical energy con-
sumed, because with these instruments it is necessary that the two currents shall
have their phases shifted accurately 90° from each other.
'
For explaining the above statement, we will refer to Figures 1A and 1B of the draw-
ing accompanying our provisional specification which shew the known diagram of a
Ferraris rotary phase current motor AA is an iron ring, built up of sheet metal and
intermediate layers of insulating material and having four polar extensions B, B, B, B
surrounding a similarly constructed iron core E. Between the polar extensions and
the core E is an air space in which is introduced, a cylinder F of conducting material
such as sheet copper, which can rotate freely on the axis G. On the polar exten-
sions B, B, are fitted two windings C C of thick wire which are connected either in
parallel or in series; on the polar extensions B₂ B, are fitted two windings D D of thin
wire which are similarly connected. If an alternating current I, passes through the
windings CC, and an alternating current I, through the windings D D and if their
phases are shifted to the extent, then the turning moment exercised on the
stationary drum F will be equal to
1.U,
When rotation ensues, a farther term is introduced which however can be neglected
for slow speeds. If now I, is proportional to the working current in a certain circuit,
if furthermore, is proportional to the pressure E₁ of this current, but shifted in
phase accurately 90° relatively to the pressure E, then
if represents the phase-shift between I, and E.
Φι
The turning moment of the drumm F F in this case indicates the work I, E₁ cos p.
The drum may be provided with a spiral spring which imparts to it a certain posi-
tion of rest and which in every position holds a certain turning moment in equilibrio
so that the position of the drum constitutes a measure for the work. A measuring
instrument is thus obtained which indicates the work of an alternating current, or, if
the pressure E, be regarded as constant, the working component of the strength of
current namely I, cos The drum can however also be made to revolve and be con.
nected with a counter, for employing the instrument, when combined with a suitable
braking arrangement, directly as a Watt hour meter.
:
Such arrangements are well known, as are also others in which for instance the
cylinder is replaced by a circular, disc, and they are, only mentioned, here, for pointing
out that with such instruments the necessary condition for correct working consists in
that the current I shall be proportional to the pressure E, and that both shall be
shifted as regards their phase by exactly 90°.
T
The present invention has for its object an arrangement which enables a phase-
shift of exactly. 90° to be established between I, and E. The extent of the phase-
shift between I, and E, will, with a certain arrangement, be dependent upon the
current curve of the current that is to be measured. The arrangement hereinafter
described enables also this phase-shift to be adjusted to 90° without much difficulty
for different current curves.

page_text: The arrangement according to this invention is shewn diagrammatically at Figure 2
The means for effecting a phase-shift of 90° between the current I, and the
pressure E..consists in introducing the windings D D in the bridge wire of a Wheatstone
bridge. The bus bars S, and S, are assumed to be connected to the source of current,
and from these the working current is taken for feeding the lamps K or motors I.
The two terminals P and Q are connected to the bus bars S₁ and S.
Between P and Q are introduced two parallel branches P M Q and P NQ, of which
the opposite sides P M and Q N have a large self induction with small resistance
while the sides P N and Q M have each a considerable resistance with small self
induction. Under these circumstances a considerable pressure will exist between M
and N and this pressure has a phase-shift relatively to the pressure between P and Q,
that is to say, relatively to the working pressure which may be of any extent.
Such phase-shift can be made smaller or greater than 90° according to the choice
of the resistances and the self induction co-efficients R and L in the branches PM Q
and P N Q. If there is no current in the bridge branch M N, the condition may be
easily established for giving the pressure between M and N a 90° phase-shift relatively
to the pressure between P and Q.
If the sides P N and Q M have no self-induction and an equal resistance R, and if
the sides P M and Q N have equal resistances R, and an equal self-induction
co-efficient L₂ (Figure 3), then with a sine current the condition for the phase-shift of
where n is the frequency of the current.
Measuring apparatus of the above described kind can be constructed of great
sensitiveness, so that only very small currents or quantities of energy need exist in
the windings D D. Correspondingly, the currents in the branches PM Q and PN Q
of the bridge need not be great and the entire apparatus requires no considerable
expenditure of electric energy.
The equality of the self induction co-efficients and resistances in opposite branches
of the bridge was only assumed for the sake of simplicity.
The object aimed at can also be attained if for instance the branch P N Q has no
The
self induction. Capacity can also be substituted for ohmic resistance.
condition that the current flowing between M and N shall have a phase-shift of 90°
relatively to the pressure between P and Q can be fulfilled in various ways.
It is furthermore not necessary that for the production of the two self-induction
co-efficients two different apparatus should be employed; two coils can be used
which are wound one over the other and have a common iron core.
The adjustment of the phase-shift is effected in a simple manner, by varying
either the self-induction of the resistance in one or both branches P M Q, and
PNQ.
For this purpose the one coil of a sensitive dynamometer, which with resistance in
series shall have exactly the same resistance and the same self-induction as the coils
DD with the resistance W in series with them, can be introduced between M and N,
while through the other coil a current is sent which has the same phase as the
working pressure.
The dynamometer will swing to the one side or the other according as the angle
of the phase-shift is greater or smaller than 90°, and it will remain in the middle
position if the angle is exactly 90°, so that it will be seen that the desired phase-
shift of 90° can by this means be accurately and readily adjusted.
An arrangement for working or for starting single phase current motors is shewn
at Figure 4. CC is the winding through which the current flows continuously and
which is connected up by the switches A, A₂. D D is the auxiliary winding which
produces a second magnetic field, whose axis with a bi-polar motor such as shewn, is
situated at right angles to the axis of the field produced by C C.
The winding D D as a rule only receives current for starting, and can therefore be

page_text: cut out by the switches A, A. This auxiliary winding is connected up as bridge of
the bridge connection between M and N.
As electromotive forces will appear in the auxiliary winding D D when the motor
is running a cutting out switch A must be provided in order that when the switch A
is open, currents may not appear in the bridge. Experiments shew that with this
arrangement a very powerful torque can be obtained at starting.
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. Method of dividing a single alternating current into two alternating currents
whose phases are shifted relatively to each other through any desired angle consisting
on the one hand in directly employing the said alternating current, or a branch
thereof having the same phase, and, on the other hand, employing a branch circuit
which constitutes the bridge wire of a Wheatstone's bridge introduced between the
terminals of the working circuit, and whose main branches contain, in addition to
Ohmic resistances, either suitably distributed self induction or capacity or both,
substantially as described.
2. A measuring apparatus operating according to the method referred to in the
first claim, consisting of two coils or groups of coils shifted in space relatively to each
other and influencing a rotatable suspended cylinder or equivalent device of any
suitable metal, in combination with a Wheatstone's bridge device such as is referred
to in the first claim, in such manner that the one coil or group of coils is included in
the working circuit while the other is included in the bridge wire of the Wheatstones
bridge, substantially as described.
3. The employment of apparatus operating according to the method set forth in
the first claim for working or starting single phase alternate current motors,
substantially as described.
Dated this 20th day of October 1907