An Improved Method of Automatic Regulation in Dynamo Machines.
Year: 1889

page_text: Date of Application, 26th Feb., 1889
Complete Specification Left, 26th Nov., 1889-Accepted, 28th Dec., 1889
'An Improved Method of Automatic Regulation in Dynamo
Machines.
I, JOSIAH SAYERS, of Twenty-four Glycena Road Lavender Hill, S. W. in the County
of Surrey Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
This invention has reference to an arrangement whereby the regulation of E.M.F.
in a dynamo, driven at a variable velocity, is automatically effected. The machine
thus automatically governed is separately excited by some external source of E.M.F.
which is approximately constant. A set of secondary batteries may be used with
advantage for this purpose. In the same circuit with this exciting battery and
actuated by the same driving shaft as the main dynamo, a small controlling dynamo
is interposed which is preferably shunt wound. This machine is so arranged as
to oppose the E.M.F. by which the main dynamo is excited. The characteristic
curves of magnetisation in the two machines may be so adjusted as to give approxi-
mately a constant potential difference at the brushes of the main machine under
very considerable variations in the speed, or the adjustment may be made so as to
cause this potential difference to vary in any desired manner with the speed.
Dated the 26th day of February 1889.
JOSIAH SAYERS.
An Improved Method of Automatic Regulation in Dynamo
Machines.
I, JOSIAH SAYERS of 24 Glycena Road, Lavender Hill in the County of Surrey,
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:-
This Invention has reference to an arrangement whereby the regulation of electro-
motive force in a dynamo driven at a variable velocity is automatically effected.
The machine thus automatically governed is separately excited by some external
source having a constant or approximately constant electromotive force. A secondary
battery may be used with advantage for this purpose. In the same circuit with this
exciting battery, and connected to the same motor or driving shaft as the main
dynamo, so as to be subject to the same relative variation of speed, a small controlling
dynamo is interposed, this machine being so arranged as to oppose the electromotive
force, by which the main dynamo is excited. The working of the two machines is so
arranged with reference to their characteristic curves of magnetisation as to give a
constant or approximately constant potential difference at the brushes of the main
machine under very considerable variations in the speed, or the adjustment may be
made so as to cause this potential difference to vary in some desired manner with the
speed.
I will now describe more particularly one way of carrying out my invention.
Fig. I. Sheet I of the drawings accompanying & forming part of this my complete
specification, shows diagrammatically the manner in which I prefer to carry out my
invention. I do not however bind myself to this actual arrangement of the connections
here shewn and described, as it may be varied to produce the same results without
departing from the principle of, the invention.
represents the main machine of which the electromotive force at the brushes is
required to be, for instance constant, although subject to variation of speed, and of

page_text: which the field magnet F. F. is separately excited by the current due to the resultant
electromotive force of the combination in series, of the opposing electromotive forces
of the accumulator B and the controlling machine C.
In the case of a dynamo which is required to have a fairly constant electro-
motive force through a large range of speed, it is preferable to so arrange the
proportions of the combination that at the minimum speed at which the combination
shall be required to be self regulating, the magnetisation of the controlling machine C
shall be at or about the value which on the characteristic curve of magnetisatiou
would be indicated by the upper end of the nearly straight part of the curve, that is at
the valve above which the permeability of the iron begins to rapidly decrease.
The controlling machine C may be shunt wound, but I prefer that it should be
excited by a combination of a shunt winding S acting together with a winding St in
series with the external circuit of the controlling machine C, that is in series with the
field. magnet coils or winding f, f, of the main machine M. As an illustration, I have
found that with certain machines I obtained good results by making the proportions
of the two windings S and S¹ of the controlling machine C such that at the minimum
required speed before mentioned, the number of ampère turns of each coil were equal
or nearly so, but this ratio will depend upon the design and proportions of the other
parts of the machines.
The magnetisation of the main machine M at the minimum speed at which regulation
is to commence may advantageously be as nearly as possible at the same point of
the characteristic of magnetisation, as in the case of the controlling machine C, that is
at the top of the very nearly straight part of the curve.
I have given certain proportions above for the purpose of illustration but I do not
limit myself to these proportions.
The proportion of the electromotive force of the accumulator in this arrangement to
the opposing electromotive force of the controlling machine C at the minimum speed
depends upon the range of variation of speed, through which it is desired that the
combination shall be self-regulating.
It will be understood from the foregoing description and explanation that the con-
trolling machine C, acting as it does to oppose or partly neutralise an electromotive
force higher than its own is in reality an electric motor, as its speed is never high
enough to enable it to send a current in the direction proper to it as a generator.
The word dynamo is, in this Specification, used indifferently for generator or
motor.
Fig. II. Sheet II of the accompanying drawings shews diagrammatically the
application of this Invention to an ordinary case of electric lighting where the lamps
are used in combination with a secondary battery B, which battery, or it may be a
portion of it, is made to act as the constant electromotive force constituent of the self-
regulating combination which is the object of this invention.
Similar parts in
Figs. I & II are indicated by similar letters.
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 use, for the purpose of regulating a dynamo subject to variations of speed,
of another dynamo subject to the same relative variations of speed, in combination
with a constant or approximately constant source of E.M.F., such as a secondary
battery, substantially and as in the manner, described.
Dated this Twenty-sixth day of November 1889.