provements in Electric Motors and meters adapted for use with Alternating Currents.
Year: 1898

page_text: provements in Electric Motors and meters adapted for use with
Alternating Currents.
We, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, and FRANK
CONRAD, of 709, Whitney Avenue, Wilkinsburg, both in the State of Penn-
sylvania, United States of America, Electrical Engineers, do hereby declare
the nature of this invention to be as follows:-
:-
This invention relates to electric motors adapted to be operated by alternating
currents and more especially to such motors as are suited for use in electricity
meters.
The object of the invention is to provide a new meter operated by a shif
magnetic field upon principles now well known to electricians.
The novel feature of the present invention consists in the arrangements for
producing the shifting magnetic field, that is to say, for varying the distribution
of the magnetic flux through the secondary member such flux being due to one
coil and the variation being produced by another coil which is so disposed as
to reinforce the flux due to the first coil in one part of its magnetic circuit and
oppose the flux due to such coil in another part of its magnetic circuit. By
this method of varying the distribution, the fluxes due to the coils can be
strengthened and concentrated by the use of iron to a much larger extent than
has previously been possible with this class of meter and consequently the
amount of copper required in the coils of the motor reduced thereby rendering
the meter less expensive to construct.
In the accompanying drawings:-
-
Figures 1, 2 and 3 are views illustrating an electricity meter actuated by a
motor which operates on the principle underlying our invention.
Figure 1
being a front elevation, Figure 2 a vertical section at right angles to Figure 1
and Figure 3 being a plan with the counting mechanism removed.
Figure 4 is a diagram of the circuits of the instrument.
Figure 5 is a detail sectional view of the meter motor provided with an anti-
retarding device.
Figure 6 is a front elevation of the motor shewn in Figure 5, the windings
being diagrammatically indicated.

page_text: Figure 7 is a view similar to Figure 6, but embodying certain modifications
in the windings.
Figure 8 is a diagrammatic end elevation of a modified form of motor, and
Figure 9 is a similar view of a further modification.
The
Referring now to Figures 1 to 7, 1 is the core of the primary member built
up of laminæ clamped between two plates 7 and having a pole piece 2 on one
side and two pole pieces 3 and opposite the same with a gap 6 between, the
gap 6 may be filled up with nonmagnetic material. The shape of the core is
best seen from Figure 6. The secondary member which consists of a circular
metal disc 14 which is fixed to a spindle 15 supported in bearings 16 projects
into the gap 5 between the pole piece 2 and the opposite pole pieces 3 and 4.
The upper part of the spindle 15 engages with a suitable counting device indi-
cated at 17 with indicating dials 18. The magnetization of the core 1 is pro-
duced by two coils one of which 11 is wound upon the pole piece 2 and the
magnetic flux due to this coil has a choice of two paths one through the pole
piece 3 passing round the left hand branch- of the core and the other passing
through pole piece 4 and round the right hand branch (see Figure 6).
other coil is made in two parts 8-8 one on each branch of the core and the
two parts of this coil are arranged so as to magnetize the core as a simple ring
the flux passing practically across the gap 6 and only a small amount of leakage
occurring at the gap 5. It will therefore be seen that the magnetic flux due
to the coil 8-8 reinforces that due to the coil 11 in one branch of the core and
opposes that in the other branch of the core. In the diagrams Figures 6 and 7
the coil 11 is indicated as being in series with the circuit 9, 10 the energy
supplied to which it is desired to measure, the coil 8-8 shunting the said
circuit. For reasons well known to electricians it is desirable that the mag-
netic fluxes due to the two coils 8-8 and 11, should be exactly in quadrature
and for securing this various devices may be employed, for example, an induc-
tive resistance 12 may be joined in series with the shunt coil 8--8, or two
coils 13 forming a closed circuit may be placed one at each branch of the core
connected if desired by a variable resistance 13¹, or any other suitable phase
adjusting device may be used.
In order to retard the speed of the disc 14 it may be caused to rotate between
the poles of a permanent magnet 19 or other suitable means may be employed.
Since the series coil of the instrument tends to retard the speed of the disc
to a greater or less extent depending upon the volume of current flowing
through it, it may be found desirable in some cases to employ magnetic plates
or shields 20 adjustably supported by a bracket 21 (see Figures 5 and 6) in
order to divert some of the lines of force in the direction of rotation of the
disc. The distortion of the field due to these plates will obviously vary as the
current through the coil 11 varies, and it will therefore counteract the variable
retarding effect which would be otherwise incident to a varying current in
the series coil.
To compensate for the mechanical friction in the moving parts there is pro-
vided a coil 22 of high resistance located upon or adjacent to one of the coils 8,
or a single turn of copper wire 221 connected through the high resistance 2211
may be used as shewn in Figure 6. The effect of this coil is to increase the
leakage across the gap 5 and it should be so adjusted that the effect upon the
disc will be a little less than that required to start the same when the maximum
voltage is applied to the shunt coils only.
The operation of the meter which is embodied in the instrument just described
is dependent upon a difference in phase between the magnetic flux or fluxes
due to the current in the shunt coils and the flux or fluxes due to the current
in the series coil. This difference is preferably, as has already been stated 90°
for a condition of no inductive load. on the work circuit.
cuits which have substantially
In cir-
no inductive load, however, such
those supplying incandescent lamps, the phase difference between
as
the

page_text: two fluxes may be less than 90° and the instrument calibrated to
give a correct registration of the energy delivered to the translating devices.
We will assume however, for the purpose of describing the theory of operation
that the phase difference between the shunt and series currents and between the
corresponding magnetic fluxes is 90° for a condition of no lag in the external
or work circuit. When the series current is at zero and the shunt current is at
its maximum positive value, there will be little or no magnetic flux across the
air gap 5. From this point to that where the shunt and series currents are
both positive and equal, the gradually increasing magnetic flux across the air
gap 5 due to the series current will be reinforced in one half of the core 1 and
opposed in the other half. This will result in crowding the resultant flux
mainly or wholly to one side of the air gap, for example, to that portion
between the pole piece 3 and the corresponding side or edge of the pole piece 2.
As the series current increases and the shunt current decreases from this point, the
resultant flux across the air gap 5 will gradually spread out until the series
current reaches a maximum and the shunt current becomes zero, when the resul-
tant flux will be symmetrical as regards the poles 2, 3 and 4 and the air gap.
As the shunt current approaches a negative maximum and the series current
decreases from its maximum positive value, the resultant flux will be shifted
more and more to the other side of the air gap 5, until the shunt and series
currents attain the same value. This resultant flux will be maintained at the
same side of the air gap, but will decrease in volume until the series current
reaches zero and the shunt current attains its maximum negative value, when
the flux across the gap 5 will either cease altogether or be limited to a stray
field due to the shunt current only. The operation during the remaining por-
tion of the period or cycle will be the same as that described, except that at
each corresponding instant of time, the resultant flux will be in the reverse
direction. Each succeeding cycle or period is obviously the same as that which
preceded it and the shifting magnetic field thus produced serves to rotate the
disc at a speed dependent upon the cosine of the angle of lag in the work cir-
cuit, assuming that the current and impressed electromotive force are constant.
This alternate shifting of the resulting flux from one side to the other of the
air gap 5 by reason of the alternate reinforcement and opposition of the fluxes
at these two sides will obviously be at a maximum where there is a phase
difference of 90° between the shunt and series current, and this resultant shift-
ing field will decrease in strength and duration as the phase angle between
the two currents decreases, until the two currents are in step, when the resul-
tant field will be mainly or wholly located at one side of the air gap 5. Under
this condition the resultant flux will be alternately reversed in direction, but
will not shift to the other side of the air gap, and hence there will be no rota-
tion of the disc.
It will be obvious that the meter may be used with slight modifications for
measuring other currents than single phase currents. Furthermore, the primary
member of the motor may be duplicated at the opposite edge of the disc or
secondary member the coils being connected in a separate circuit the currents
of which need not be in phase with that in the first circuit in such a case the
meter will indicate the total energy consumed by both circuits.
In Figures 8 and 9 the application of the principles above described for pro-
ducing a shifting magnetic field is shewn to a motor the secondary member or
armature being indicated in Figure 8 by 141, the core of the primary member
is shewn in four parts with gaps between them and having pole pieces 31
and 4. One of the operating coils 11¹ is wound round each pair of pole pieces
so as to make them of the same sign, the other coil being wound between the
polepiece as shewn at S¹ and adapted to magnetize the ring-shaped core as a
whole.
The operation of the motor will be readily understood from the description
hereinabove given. In Figure 9 the coil 11' is wound on a stationary core 24

page_text: the secondary member 141 taking the form of a ring or cylinder. For the pur-
pose of starting the motors we have shewn a circuit closing switch 24 for both
sets of coils and a variable resistance 25 in the circuit of the coils 11.
Dated the Tenth day of May 1898.
Improvements in Electric Motors and Meters adapted for use with
. Alternating Currents.
We, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, and FRANK
CONRAD, of 709, Whitney Avenue, Wilkinsburg, both in the State of Penn-
sylvania, United States of America, Electrical Engineers, 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:-
This invention relates to electric motors adapted to be operated by alternating
currents and more especially to such motors as are suited for use in electricity
meters.
The object of the invention is to provide a new meter operated by a shifting
magnetic field upon principles now well known to electricians.
In the meter constructed according to this invention there is a secondary
member which is acted upon inductively by the magnetic flux which is due to
currents circulating in coils wound upon a magnetic core and forming with it
the primary member. This magnetic core is so constructed that the magnetic
flux has more than one path open to it and the path which it takes is determined
by means of another magnetic flux which is produced by a coil having a current
passing through it which is different in phase from the current passing through
the coil which produces the first mentioned or main magnetic flux. The varia-
tion in the path of the total flux acts on the secondary member of the motor in
a well known manner and causes it to rotate and the number of rotations are
registered in the ordinary way. In such a meter, however well made the parts
are, there is always mechanical friction, and, moreover, the secondary member
sticks at the starting and in some cases will not start when very small currents
only are passed through the meter. To overcome this mechanical friction and
sticking of the secondary member, we provide another coil which is not
directly connected to the circuit in any way, but which is acted upon by a current
flowing in the flux varying coil. This auxiliary or compensating coil is placed
so that substantially all the magnetic flux due to it passes round only one of the
two paths formed by the magnetic core of the primary member.
In the accompanying drawings:
-
Figures 1, 2 and 3 are views illustrating an electricity meter actuated by a
motor which operates on the principle underlying our invention. Figure 1
being a front elevation, Figure 2 a vertical section at right angles to Figure 1,
and Figure 3 being a plan with the counting mechanism removed.
Figure 4 is a diagram of the circuits of the instrument.
Figure 5 is a detail sectional view of the meter motor provided with an anti-
retarding device.
Figure 6 is a front elevation of the motor shewn in Figure 5, the windings
being diagrammatically indicated.

page_text: Figure 7 is a view similar to Figure 6, but embodying certain modifications
in the windings.
Figure 8 is a diagrammatic end elevation of a modified form of motor, and
Figure 9 is a similar view of a further modification."
Referring now to Figures 1 to 7, 1 is the core of the primary member built
up of lamina clamped between two poles 7 and having a pole piece 2 on one
side and two pole pieces 3 and 4 opposite the same with a gap 6 between, the
gap 6 may be filled up with non-magnetic material. The shape of the core is
best seen from Figure 6. The secondary member which consists of a circular
metal disc 14 which is fixed to a spindle 15 supported in bearings 16 projects
into the gap 5 between the pole piece 2 and the opposite pole pieces 3 and 4.
The upper part of the spindle 15 engages with a suitable counting device indi-
cated at 17 with indicating dials 18. The magnetization of the core 1 is pro-
duced by two coils one of which 11 is wound upon the pole piece 2 and the
magnetic flux due to this coil has a choice of two paths one through the pole
piece 3 passing round the left hand branch of the core and the other passing
through pole piece 4 and round the right hand branch (see Figure 6). The
other coil is made in two parts 8-8 one on each branch of the core and the
two parts of this coil are arranged so as to magnetize the core as a simple ring
the flux passing practically across the gap and only a small amount of leakage
occurring at the gap 5. It will therefore be seen that the magnetic flux due
to the coil 8-8 reinforces that due to the coil 11 in one branch of the core and
opposes that in the other branch of the core. In the diagrams Figures 6 and 7
the coil 11 is indicated as being in series with the circuit 9, 10 the energy
supplied to which it is desired to measure, the coil 8-8 shunting the said
circuit. For reasons well known to electricians it is desirable that the mag-
netic fluxes due to the two coils 8-8 and 11, should be exactly in quadrature
when there is no induction or capacity in the circuit 26, and for
securing this various devices may be employed, for example an induc-
tive resistance 12 may be joined in series with the shunt coil 8--8, or two
coils 13 forming a closed circuit may be placed one at each branch of the core
connected if desired by a variable resistance 131, or any other suitable phase
adjusting device may be used.
In order to retard the speed of the disc 14 it may be caused to rotate between
the poles of a permanent magnet 19 or other suitable means may be employed.
Since the series coil of the instrument tends to retard the speed of the disc
to a greater or less extent depending upon the volume of current flowing
through it, it may be found desirable in some cases to employ magnetic plates
or shields 20 adjustably supported by a bracket 21 (see Figures 5 and 6) in
order to divert some of the lines of force in the direction of rotation of the
disc. The distortion of the field due to these plates will obviously vary as the
current through the coil 11 varies, and it will therefore counteract the variable.
retarding effect which would be otherwise incident to a varying current in
the series coil.
1
To compensate for the mechanical friction in the moving parts and to cause
the meter to start with a small current we provide a coil 22 of suitable resistance
on one branch of the primary member, such a coil as shewn at 22 in Figure 7
which consists of a suitable number of turns of wire closed upon itself and placed
so as to be acted upon inductively by the current flowing in one of the coils 8.
The effect of this coil is to increase the leakage across the gap 5 of the magnetic flux
due to the coils S, because the flux due to it will rather tend to pass across the
gap 5 than to go entirely round the other branch of the magnet circuit; there
is therefore a slight distortion of the magnetic flux produced, which is sufficient
to overcome the mechanical friction and cause the meter to start; the coils
should be so adjusted that the effect upon the disc 14 will be a little less than
that required to start the same rotating when maximum voltage is applied to.
the shunt coils of the meter only.
'

page_text: In Figure
the coil 22 is indicated as consisting of a single turn of copper
wire 22 connected through a resistance wire 22", the resistance and number of
turns being adjusted to suit the particular meter.
gap
The operation of the meter which is embodied in the instrument just described
is dependent upon a difference in phase between the magnetic flux or fluxes
due to the current in the shunt coils and the flux or fluxes due to the current
in the series coil. This difference is preferably, as has already been stated 90°
for a condition of load on the work circuit in which the current is in
phase with the E.M.F. In circuits which have substantially no inductive
load, however, such as those supplying incandescent lamps, the phase difference
between the two fluxes may be less than 90° and the instrument calibrated to
give a correct registration of the energy delivered to the translating devices.
We will assume, however, for the purpose of describing the theory of operation
that the phase difference between, the shunt and series currents and between the
corresponding magnetic fluxes is 90° for a condition of no lag in the external
or work circuit. When the series current is at zero and the shunt current is at
its maximum positive value, there will be little or no magnetic flux across the
air gap 5. From this point to that where the shunt and series currents are
both positive and equal, the gradually increasing magnetic flux across the air
due to the series current will be reinforced in one half of the core 1 and
opposed in the other half. This will result in crowding the resultant flux
mainly or wholly to one side of the air gap, for example, to that portion
between the pole piece 3 and the corresponding side or edge of the pole piece 2.
As the series current increases and the shunt current decreases from this point, the
resultant flux across the air gap 5 will gradually spread out until the series
current reaches a maximum and the shunt current becomes zero, when the resul-
tant flux will be symmetrical as regards the poles 2, 3 and 4 and the air gap.
As the shunt current approaches a negative maximum and the series current
decreases from its maximum positive value, the resultant flux will be shifted
more and more to the other side of the air gap 5, until the shunt and series
currents attain the same value. This resultant flux will be maintained at the
same side of the air gap, but will decrease in volume until the series current
reaches zero and the shunt current attains its maximum negative value, when
the flux across the gap 5 will either cease altogether or be limited to a stray
field due to the shunt current only. The operation during the remaining-por-
tion of the period or cycle will be the same as that described, except that at
each corresponding instant of time, the resultant flux will be in the reverse
direction. Each succeeding cycle or period is obviously the same as that which
preceded it and the shifting magnetic field thus produced serves to rotate the
disc at a speed dependent upon the cosine of the angle of lag in the work cir-
cuit, assuming that the current and impressed electro-motive 'force are constant.
This alternate shifting of the resulting flux from one side to the other of the
air gap 5 by reason of the alternate reinforcement and opposition of the fluxes
at these two sides will obviously be at a maximum where there is a phase
difference of 90° between the shunt and series current, and this resultant shift-
ing field will decrease in strength and duration as the phase angle between
the two currents decreases, until the two currents are in step, when the resul-
tant field will be mainly or wholly located at one side of the air gap 5. Under
this condition the resultant flux will be alternately reversed in direction, but
will not shift to the other side of the air gap, and hence there will be no rota-
tion of the disc.
It will be obvious that the meter may be used with slight modifications for
measuring other currents than single phase currents. Furthermore, the primary
member of the motor may be duplicated at the opposite edge of the disc or
secondary member the coils being connected in a separate circuit the currents
of which need not be in phase with that in the first circuit in such a case the
meter will indicate the total energy consumed by both circuits.

page_text: In Figures 8 and 9 the application to a motor of the principles above described
for producing a shifting magnetic field is shewn, the secondary member or
armature of said motor being indicated in Fig. 8 by 14 and the core of the
primary member being shewn in four parts with gaps G¹ between them and hav-
ing pole pieces 31 and 4¹. One of the operating coils 11¹ is wound round each
pair of pole pieces so as to make them of the same sign, the other coil being
wound between the pole pieces as shewn at 8¹ and adapted to magnetize the ring-
shaped core as a whole."
The operation of the motor will be readily understood from the description.
hereinabove given. In Figure 9 the coil 111 is wound on a stationary core
the secondary member 14' taking the form of a ring or cylinder. For the pur-
pose of starting the motors we have shewn a circuit closing switch 24 for both
sets of coils and a variable resistance 25 in the circuit of the coils 111.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is:
-
1. An electric motor or meter constructed and operating substantially as
described.
2. In an electric meter of the kind described a closed circuit coil which is
acted upon inductively by the current flowing through one of the magnetizing
coils so as to distort the magnetic field passing through the secondary member
and thereby cause a tendency for the secondary member to rotate sufficient to
overcome the mechanical friction of the pivots.
Dated the 9th dev of Fohru 1800
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.