Improvements in Electrical Distribution and in Starting Rotary Electric Converters.
Year: 1899

page_text: Date of Application, 11th Nov., 1899-Accepted, 27th Oct., 1900
COMPLETE SPECIFICATION.
Improvements in Electrical Distribution and in Starting Rotary
Electric Converters.
We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of our
said invention (which has been communicated to us from abroad by William
B. Potter, of Schenectady, in the County of Schenectady, State of New York,
United States of America, Electrical Engineer,) and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:-
Our present invention relates to means for starting rotary electric converters,
the object being to pernut such apparatus to be started in a distributing station
where a direct current circuit is not available. We accomplish this result by
employing an induction motor driven from the source of alternating current
supply, by which a small, direct current generator is operated and employed to
start up the rotary converters. By this system we avoid the employment of
starting resistances, reactances or transformers, and also avoid the great rush of
idle current which is so serious in practice when rotary converters are started
from the alternating current side.
The motor generator may be provided with a starting resistance and with an
adjustable resistance in its field magnet circuit for varying its voltage, or the
starting resistance may be entirely dispensed with by providing the direct
current side of the motor generator with two armatures and two independent
field magnets arranged for connection respectively with the armatures and field
maguets of the several rotary converters.
By this plan of procedure a plurality of rotary converters may be started by
the employment of a single auxiliary machine of small capacity as compared with
that of the several converters and a single small starting resistance, or with the
double armature arrangement above referred to the starting resistance may be
entirely dispensed with.
The several features of novelty will be particularly described hereinafter,
and will be definitely indicated in the claims.
In the accompanying drawings, which diagrammatically illustrate our inven-
tion, Fig. 1 is a view of a distributing station containing a plurality of rotary
converters, and an auxiliary starting generator driven by an induction motor
for starting up any of the converters; and Fig. 2 is a modification in which the
induction motor drives two separately excited direct current armatures.
Referring first to Fig. 1, 1, 2, and 3, represent the supply wires of the alter-
nating current side of a station containing a plurality of rotary converters
4, 4, 4. Current passes from the wires through a three pole switch 5, 5º, 5º,
and to three ring contacts, as indicated in the diagram, connecting respectively
with symmetrical points of the windings of the armatures of the rotary con-
verlers, the commutated sides of which discharge through brushes 6, 7, etc.,

page_text: adapted to be connected by a two pole switch 8, 8, 8, with a pair of bus burs
communicating with a direct current distributing circuit.
the
In ordinary practice the converter is brought up to speed by current from
the alternating mains, through a reactance or auto converter, the field circuit
being open, and after synchronous speed is attained or nearly attained
field circuit is closed and the rotary falls into step, when it
can bo thrown on to the direct current muins. This operation in
practice is exceedingly difficult and troublesome, and requires a current frequently
largely exceeding in voltage the current which the machine tukes in normal
operation.
Under our present plan, we dispense with these auxiliary starting resistances
and employ an auxiliary induction motor, the rotary magnetic field or primary
member of which is indicated at 9, and the secondary member at 10.
The latter is indicated as the well known type of squirrel cage winding, the
construction of which is well understood by those familiar with induction motors.
The motor may be fed from the same leads or bus-bars 1, 2, 3, which supply the
rotary converters.
The system is shown as applied to a tri-phase circuit; it will of course be
understood, however, that the invention is applicable to an alternating current
system of any type or number of phases. The rotary member of the induction
motor drives a direct current armature 11, the field magnet, 12, of which is
governed by a variable resistance, 13, to vary the potential of the machine. The
machine is coupled through an adjustable resistance, 14, and a two-pole switch 15,
with the direct current side of the rotary converter, 4. Switches 15, 15³, in
series relation with the switch 15, may be employed to start up the converters 4⑈
and 4b; these several switches are so arranged that only a single converter can
be started at a time. The arrangement will be clear from an inspection of the
diagram where it will be seen that any one of the switches 15, 15 or 15 can
draw current from the non-starting position of either of the other two switches
between it and the starting generator. No claim is herein made, however, to
this arrangement as it is not of our invention. With this organization, when
the controlling switch for the induction motor is closed, the alternating current
drives the auxiliary machine 11. The switch may then be closed, assuming
that machine 4 is to be started, and placed in the position indicated in the
diagram. The starting resistance 14 will then be gradually cut out, thus
admitting more current gradually to the direct current side of the rotary con-
verter and increasing its speed. Its speed may be still further increased by
strengthening the field magnet 12 of the auxiliary generator by suitable adjust-
ment of the regulating switch 13. When the converter has been raised to a
speed where it is in synchronism with the alternating source, the switch 5 may
be thrown and the machine then becomes self exciting, and the switch 15 may
be opened. The controlling switch for the distributing circuit, shown at 8, may
be then closed on the direct current bus-bars. Similarly, any other machine
of the group installed in the station may be started.
With an organization such as above described, the several rotary converters
may he started one at a time by a small auxiliary machine of from five to
ten per cent. of the capacity of each rotary converter, and with a single auxiliary
resistance.
In the plan employed in Fig. 2 the starting resistance 14 is dispensed with,
and the induction motor driven generator is provided with two independent
armature 11, 11, adapted to be independently connected, respectively, with
the field magnet and armature on the direct current side of the rotary generator.
Two independent trains of controlling switches for the armature and field magnet
are employed as shown at 16, 16, 17, 17. In the field magnet circuit is inter-
posed a circuit breaker or switch 18, 18, to permit the closing of but a single
field magnet circuit at a time when the station is being started up. Switches 8.8.
similar to those described in connection with Fig. 1, for connecting the direct

page_text: current side of the several rotary converters with the distributing bars of the
direct current circuit are provided. Each field magnet of the auxiliary generator
is provided with an independently regulable resistance 13, 13, both in paralle
branches of the armature circuit which supplies the field magnet of the rotary
converters. Thus, in starting up the machines, with this organization, the
induction motor 9 is first started by closing its switch on the alternating current
side. The switch 18 in the field magnet of the converter is then closed, and
the switches 16 and 17 put in the position indicated in the diagram, thereby
closing the two armature-circuits of the auxiliary generator upon independent
circuits of the rotary converter. As the latter accelerates in speed, its armature
current may ho increased by adjusting the resistance 13 and increasing the
field magnet strength of the machine 11, as the field magnet coil 13 is in shunt
to the field coil 13 it may be built up more gradually than if in circuit with
the armature of the rotary converter. The field regulating resistance 13 may
then be adjusted to increase the voltage on the field magnet of the rotary con-
verter and when the latter rises to synchronous speed, its switch may be thrown
so as to couple it in circuit with the alternating current source of supply.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is:-
1-In a system of electrical distribution, the combination of a plurality of
rotary converters, means for coupling them into operative relation to alternating
or direct current circuits, a direct current generator for starting said rotary con-
verters into operation upon the direct current side, and an induction motor
driven by the alternating current source for operating said auxiliary generator.
2-A system of electrical distribution, comprising a plurality of rotary con-
verters connecting on its several sides with direct and alternating current
circuits, respectively, controlling switches for said circuits, an auxiliary starting
generator and switches for connecting it with the direct current side of the
several rotary converters, means for regulating the potential of said generator,
and an induction motor fed from the alternating current source of supply, for
operating said generator.
3-A system of electrical distribution comprising a rotary converter, means for
connecting its two sides with direct and alternating current circuits respectively,
an auxiliary direct current starting generator coupled to an induction motor in
operative relation to the alternating source, said generator being provided with
independent windings, means for independently varying the voltage of each
winding, and connections for said windings with the field magnet and armature
of the rotary converter on its direct current side.
4-A system of electrical distribution comprising a plurality of rotary converters,
switches for coupling them independently into direct and alternating circuits at the
two sides, a direct current starting generator provided with two windings of inde-
pendently-regulable voltage, and a switch in the field magnet circuit of the
several converters.
5-A system of electrical distribution comprising a rotary converter having
a direct current starting generator provided with armature windings rotating in
independently regulable fields of force. said windings connected respectively
with the field magnet and armature of the converter, both field magnet coils of
the starting machine being connected with the field magnet charging circuit of
the rotary converter.
G-The combination with a source of alternating current of a rotary converter
fed therefrom, means for transforming current from said mains to direct current,
and means for causing said direct current to start the rotary converter.
7 The method of supplying direct current to a distribution system or trans-
lating device, which consists in generaling alternating current, converting a
portion of said current into unidirectional current, utilizing said unidirectional

page_text: current to start a transforming device, and thereafter utilizing said transforming
device to transform said alternating current to direct current and supplying said
direct current to the system or translating device.
Noted this Uct dor of October 1800
THE BRITISH THOMSON-HOUSTON Co. LTD.,
ALFRED CLEMENTS,
Assistant Secretary.
A. R. MONKS,, }
Directors.