Improvements in Compound Winding of Groups of Dynamos.
Year: 1891

page_text: Date of Application, 5th Dec., 1891
Complete Specification Left, 3rd Sept., 1892-Accepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in Compound Winding of Groups of Dynamos.
I, JOHN MACINTOSH MACKAY MUNRO, of 136 Bothwell Street, Glasgow,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
"
When in transmitting electrical energy it is desirable to maintain at a distributing
switch or feeding point a constant potential differance or a potential differance
varying in some definite way, the most usual method of doing so is to "compound"
or "over-compound" wind the dynamo so as to give such rising electro-motive force
at the dynamo terminals as will compensate for the varying loss of pressure with
varying current in the conductors which connect the dynamo with the switch or
point. This cannot be done by usual methods with groups of dynamos.
The same ends can be fairly well attained by such arrangements as the following.
Let there be say for example three dynamos each with an output of 100 amperes
situated one mile from the distributing switch and it is desired to keep the
distributing switch at a constant potential. Let the conductors be divided up so
that instead of one pair of conductors between dynamos and switch board giving a
fall of say 15 volts with 300 amperes there are three separate pairs of conductors
each giving 15 volts fall with 100 amperes. These pairs of conductors are then
connected together at the switch board but otherwise insulated the one from the
other. When one dynamo is working, only one pair of conductors is used and the
machine being over compounded in the usual manner for a 15 volt rise between
open circuit and full load the arrangement so far attains the end desired. But if
now a second dynamo is added on to meet a load say of a little over the capacity of
the one machine, the current in the compound (main) coils of the machine is reduced
and so too is the electro-motive force of the machine, consequently the fall in the
line is not compensated for. But at this juncture and by the same movement that
switches on the second dynamo the brushes of the two machines are connected
together the positive to the positive and the negative to the negative (this to avoid
reversal by back currents) and a second pair of main conductors is joined to the
first pair at dynamo end. Thus the rise of electro-motive force in the machines is
again brought approximately into relation with the fall in the main conductors.
This method, however, does not at all times fully utilize the copper in the line,
therefore I have devised the following arrangement which I will now proceed to
describe. Instead of separate pairs of conductors I use only one pair or its equiva-
lent, (unless of course in cases where the current is to be sent in various directions)
and instead of winding the magnet of each machine individually with its own main
wire carrying its own main current, I propose instead of, or in addition to this, to
pass the main line current or a shunted proportion of it in succession round the
coils on all the dynamos of the group. When any dynamo is not in use its coils
are bridged over by a switch to avoid wasting energy and maintaining magnetism
when not required. Let the group of machines be otherwise ordinary shunt wound
dynamos. When one or more of these are at work the main line current being
passed a few times round their magnets strengthens the magnetism and so equally
increases the electro-motive force of all the machines at work almost proportionately
to the total current in the line, and thus, the resistance of the line being practically
constant, counterbalances the fall in the line. Where each dynamo is driven by a
separate motor as when dynamos are coupled direct each to its own high speed
engine it may often serve the same purpose although the number of the turns or the
proportion of the main line current passed round the magnets is reduced in all but
one machine or even abolished altogether save in this one machine. When this one

page_text: machine (running say at constant speed) has its electro-motive force increased by
the increased line current passing round its magnets the other engines will speed
up a little to attain the same electro-motive force in their shunt wound dynamos
just as a row of engines driving dynamos feeding on to one omnibus bar con-
trolled more by load than by governor and with stop-valves full open can be
kept in fair unison by means of the stop-valve of any one engine, when the
balance and regulation can be thereby better effected; then in addition to this
main line current there may be a few turns of the main circuit of the separate
machines passed round their own magnets after the usual manner of under
compounding, but in this case when a machine is switched into circuit its brushes
may be connected with the brushes of the machines already at work so as to avoid
all risk of reversal.
Dated thin 4th day of Dasember 1901
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.
COMPLETE SPECIFICATION.
Improvements in Compound Winding of Groups of Dynamos.
I, JOHN MACINTOSH MACKAY MUNRO, of 136 Bothwell Street, Glasgow,
Electrical Engineer, 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 :—
<<
"
When in transmitting electrical energy it is desirable to maintain at a distributing
switch or feeding point a constant potential differance or a potential differance
varying in some definite way, the most usual method of doing so is to "compound
or over-compound" wind the dynamo so as to give such rising electro-motive
force at the dynamo terminals as will compensate for the varying loss of pressure
with varying current in the conductors which connect the dynamo with the switch
or point. This cannot be done by usual methods with groups of dynamos.⚫
The same ends can be fairly well attained by such arrangements as the following.
Let there be say for example three dynamos cach with an output of 100 amperes
situated one mile from the distributing switch, and it is desired to keep the dis-
tributing switch at a constant potential. Let the conductors be divided up so that
instead of one pair of conductors between dynamos and switch-board giving a
fall of say 15 volts with 300 amperes there are three separate pairs of conductors
each giving 15 volts fall with 100 amperes. These pairs of conductors are then
connected together at the switch-board, but otherwise insulated the one from the
other. When one dynamo is working, only one pair of conductors is used, and the
machine being over compounded in the usual manner for a 15 volt rise between
open circuit and full load the arrangement so far attains the end desired. But if
now a second dynamo is added on to meet a load say of a little over the capacity of
the one machine, the current in the compound (main) coils of the machines is
reduced, and so too is the electro-motive force of the machine, consequently the fall
in the line is not compensated for. But at this juncture, and by the same move-
ment that switches on the second dynamo the brushes of the two machines are
connected together, the positive to the positive and the negative to the negative
(this to avoid reversal by back currents) and a second pair of main conductors is
joined to the first pair at dynamo end. Thus the rise of electro-motive force in the
machines is again brought approximately into relation with the fall in the main
conductors.
This method, however, does not at all times fully utilize the copper in the line,
therefore I have devised the following arrangement which I will now proceed to
describe. Instead of separate pairs of conductors I use only one pair or its equi
valent (unless of course in cases where the current is to be sent in various directions)
and instead of winding the magnet of each machine individually with its own main

page_text: wire carrying its own main current, I propose instead of or in addition to this, to
pass the main line current or a shunted proportion of it in succession round the
coils on all the dynamos of the group. When any dynamo is not in use its coils are
bridged over by a switch to avoid wasting energy and maintaining magnetism when
not required. Let the group of machines be otherwise ordinary shunt wound
dynamos. When one or more of these are at work the main line current being
passed a few times round their magnets strengthens the magnetism and so equally
increases the electro-motive force of all the machines at work almost propor-
tionately to the total current in the line, and thus the resistance of the line
being practically constant, counterbalances the fall in the line. Where each dynamo
is driven by a separate motor as when dynamos are coupled direct each to its own
high speed engine it may often serve the same purpose although the number of the
turns or the proportion of the main line current passed round the magnets is reduced
in all but one machine or even abolished altogether save in this one machine.
When this one machine (running say at constant speed) has its electro-motive force
increased by the increased line current passing round its magnets the other engines
will speed up a little to attain the same electro-motive force in their shunt wound
dynamos just as a row of engines driving dynamos feeding on to one omnibus bar
controlled more by load than by governor and with stop valves full open can be
kept in fair unison by means of the stop-valve of any one engine, when the balance
and regulation can be thereby better effected; then in addition to this main line
current there may be a few turns of the main circuit of the separate machines
passed round their own magnets after the usual manner of under compounding, but
in this case when a machine is switched into circuit its brushes may be connected
with the brushes of the machines already at work so as to avoid all risk of
reversal.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The method of compounding or over compounding winding of groups of
dynamos (feeding on to one omnibus bar) by means of the whole or part of the
current in the omnibus bar, substantially as described.
2. The regulation of a group of dynamos by means of one of their number com-
pounded or over compounded with coils carrying all or a proportion of the current
in omnibus bar, substantially as described.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.