An Harmonic Commutator for Alternating Currents.
Year: 1888

page_text: ROYIDIONAL DI MUIFICATION.
An Harmonic Commutator for Alternating Currents.
I AMBROSE MYALL of 21 Cockspur Street in the County of Middlesex Civil
Engineer do hereby declare the nature of this Invention which has been com-
municated to me from abroad by Walter Judd of Hong-Kong, Electrician, to be as
follows :-
The object of this invention is to automatically commutate alternating currents by
means of an harmonic reed or vibrator (preferably polarized) tuned to vibrate in
harmony with the number of alternating currents given out by the generator.
In a circuit which contains a transformer, the harmonic reed may be put into
vibration in the well known manner by an electro magnet operated by the primary
or main current and by means of suitable mechanism and contact pieces made to
reverse the direction of the secondary current with each upward and downward '
movement. The reed will automatically maintain its synchronism with the generator
so long as the latter is maintained at the speed for which the former is adjusted.
The contacts will only be broken when the reed attains its zero or middle position,
which will also be at the moment when the current is at zero, or nearly so.
To prevent sparking, condensers of suitable capacity or resistance, either in
combination with each other or singly may be inserted between the contact pieces in
the well known manner.
T 10th J
SML 1000

page_text: COMPLETE SPECIFICATION.
An Harmonic Commutator for Alternating Currents.
I AMBROSE MYALL, of 21 Cockspur Street, in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention, which has been com-
municated to me from abroad, by Walter Judd, of Hong Kong, Electrician, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
The object of this invention is to automatically commutate alternating currents,
by means of a harmonic reed, or vibrator (preferably polarized) tuned to vibrate in
harmony with the number of alternating currents given out by the generator.
In a circuit which contains a transformer, the harmonic reed may be put into
vibration in the well known manner by an electro-magnet operated by the primary
or main current, and by means of suitable mechanism and contact pieces made to
reverse the direction of the secondary current with each upward and downward, or
to and fro movement. The reed will automatically maintain its synchronism with
the generator so long as the latter is maintained at the speed for which the former
is adjusted. The contacts will only be broken when the reed attains its zero or
middle position, which will also be at the moment when the current is at zero or
nearly so. To prevent sparking, condensers of suitable capacity, or resistances, either
in combination with each other, or singly, may be inserted between the contact
pieces in the well known manner.
In the accompanying sheet of drawings, Fig. 1 represents diagrammatically the
arrangement of my harmonic commutator, as applied to commutate, or convert,
the alternating current, from a dynamo, into a continuous current for working al
motor, electric lamp, or other desired instrument.
In the said drawings D is a dynamo or generator producing an alternating current,
passing through the circuit dd. This circuit includes the primary coil of the transformer T
and the coils of the electro-magnets E E. R is a harmonic reed or vibrator, placed
between and actuated by the poles of the magnets E E. At its upper and free end
it carries two contact pieces r r, insulated from it and from each other. These
contact pieces play between four contact pieces c c c c, on the same principle as an
ordinary reversing switch, such as is used in electrical testing when it is desired to
reverse say the direction of a battery current through a galvanometer. These
contacts may be either fixed or sliding, or rendered yielding by a spring. The
secondary coil of the transformer T is connected to the contact pieces cccc, in the
manner shewn, while the motor, lamp, or other instrument M, required to be operated,
is connected as shewn to the contact pieces r r on the reed, so that the alternating
currents produced in the secondary coil of the transformer T, will, by the action of
the reed R be converted into a continuous current passing through and operating
the instrument M. It is obvious that if preferred the secondary coil of the
transformer T may be connected to the pieces, while the instrument M may be
connected to the pieces c c c c, as shewn in Fig. 2.

page_text: As an alternating current passes through a zero point at every change of direction,
the vibrating reed R will, if synchronising with these changes, be at its central or
zero position at the same time, viz. when there is no current passing from the
dynamo or generator. By careful adjustment it can be secured that the reed shall
break contact very nearly at this zero moment, thus reducing the difficulties due
to sparking. These may however be overcome by the insertion of! condensers, or
resistance coils, or both, in the well-known manner to absorb the current at the
infinitesimally short period of breaking contact.
As it is necessary that the rate of vibration of the reed R shall always keep time
with the rate at which the alternating currents are produced by the dynamo, i.e.,
with the speed of revolution of the latter, the following arrangement is shewn for
automatically causing the reed to synchronize with the dynamo, notwithstanding
changes in the rate of rotation.
S is a solenoid placed in a shunt circuit on the circuit of the primary coil of the
transformer T, and having a soft iron laminated core s, operating a plunger P in a
cistern of mercury, or other suitable fluid p. This cistern is connected by a tube V,
to a tube v attached to the reed R. As the current from a dynamo, other things
being equal, varies with its speed, it is clear that, the greater the current the
greater the effect upon the core s of the solenoid. And the plunger P operated by
the said core, being properly proportioned and adjusted, will so vary the height of
the mercury in the tube v, that the vibrations of the reed R will always keep time
with the rate at which the currents are produced by the dynamo, and it is obvious
that such regulation of the rate of vibration will be effected without interruption of
the action of the reed.
It will be understood that the arrangement shewn in the drawings is merely
diagrammatic, and that such arrangement may be modified in certain details
without departing from the essential principles of my invention; thus for example in
place of the transformer T, having a closed magnetic circuit, an ordinary induction
coil with an open magnetic circuit may be employed. Moreover I do not necessarily
confine myself to the employment of a solenoid operating a plunger in a cistern of
mercury for regulating the rate of vibration of the reed R, as any other device may
be used for this purpose, which will fulfil the required conditions."
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is :-
1. A harmonic commutator R for converting an alternating into a continuous
current, substantially as herein set forth.
2. The combination with a harmonic, commutator, for converting an alternating
into a continuous current, of a device for automatically regulating the rate of vibra-
tion, without interrupting the action of the said commutator.
3. In a harmonic commutator, for converting an alternating into a continuous current,
the device for automatically regulating the rate of vibration of the said commutator,
consisting of a solenoid S operating a plunger P in a cistern of mercury, or other
suitable fluid, in such manner as to vary the height of the said fluid in a tube
attached to the vibrating commutator, substantially as herein set forth.
Dated this 20th day of December 1888.
AMBROSE MYALL,
21, Cockspur Street, S.W: