A Method of and Apparatus for Starting Alternating Current Electro- motors or Bringing them up to Synchronism.
Year: 1899

page_text: Date of Application, 11th Apr., 1899 - Accepted, 17th June, 1899
A Method of and Apparatus for Starting Alternating Current Electro-
motors or Bringing them up to Synchronism.
I, WILLIAM Du Bois DUDDELL, of 47, Hans Place, Chelsea, in the County
of London, 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:-
-
My invention relates to the starting of alternate current motors, and is
especially applicable to motors of the Froment or attracted iron type and to
motors which while not intended to work as attracted iron motors when running
at their synchronous speed may yet be brought up to synchronism by using them
as attracted iron motors by means of my invention. By the attracted iron type
of motor I mean not only those motors in which stationary electro-magnets
solenoids or windings attract, when a current flows through them, movable pieces
of soft iron, but also those motors in which movable electro-magnets coils or
windings attract, when a current flows through them, fixed pieces of iron, so
as to move.
I will now proceed to describe my invention by reference to the accompanying
drawing, which represents, in diagrammatic elevation, my invention applied to
a motor having moving soft iron pieces and stationary electro-magnets.
Referring now to Figure I, I attach to the shaft 1 of the motor a cam or
equivalent device 2, which actuates a contact maker 3 of any convenient type.
This cam makes and breaks contact as many times in each revolution of the
moving part as there are pieces of iron to be attracted during each revolution
of the said moving part. Thus in the case illustrated contact is made and broken
four times in each revolution. This contact maker 3 is in series with the electro-
magnets 4, 5; and the cam is fixed on the shaft in such a position relative to the
pieces of iron 6, 7, 8 and 9 that when the contact is closed the alternating
current flows through the magnets 4, 5 causing them to attract the pieces of
iron 6, 8 respectively thus turning the shaft and the cam until the said pieces
of iron 6, S are opposite the poles of the magnets 4 and 5. The cam then causes
the contact to be broken and the attraction of the magnets to cease.
The pieces
of iron and shaft continue to turn on account of their moment of inertia until the
next pieces of iron 9, 7 are near the magnets 4 and 5 respectively, when the
cam again causes the contact maker to complete the circuit and the magnets to
attract the iron as before. This cycle of operations is repeated with gradually
increasing frequency and the shaft caused to rotate with increasing speed. When
the synchronous speed is reached the contact maker may be prevented from in-
terrupting the circuit any more either by short circuiting it or preferably by
turning the contact maker on the centre 10 into the position shown in broken
lines so that the cam no longer works it when the motor will continue to run as
a synchronous motor.
I have indicated the circuit by the leads 11, 12, 13, 18, from which it will

page_text: be seen that the circuit is made and broken between the contact points 14, 15
attached to the springs 16, 17 carried on the lever 18 of insulating material.
Instead of the cam 2 and separate contact maker 3 I sometimes use a rotating
contact maker either driven by the shaft of the motor, or preferably fixed on it,
the said rotating contact being arranged so as to make and break the electric
current the same number of times as there are either fixed or moving pieces of
iron to be attracted.
It is obvious that my invention may be used in the case of motors in which the
electro-magnets or coils which carry the current rotate and the attracted iron is
stationary.
To apply my invention in the case of motors which are not of the attracted
iron type I may add auxiliary pieces of iron which can be attracted or, prefer-
ably, I may use the iron cores poles or polar projections or other suitable iron
parts of the motor as the pieces of iron to be attracted. The invention may then
be applied as before described except that I provide a switch which may be
actuated by hand or automatically to change the connections, when the syn-
chronous speed is reached, from those for the attracted iron motor to those for the
synchronous motor of whatever type it may be.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:
1. The method of starting alternating current electro-motors or bringing them
up to synchronism substantially as set forth.
2. In apparatus for starting alternating current electro-motors or bringing
them up to synchronism the combination with the motor of a cam driven by the
said motor and a contact actuated by the said cam substantially as set forth.
Datod this 11th day of i„.61 1900
Datod this 11th day of April 1900
For the Applicant,
J. G. LORRAIN, M.I.E.E., M.I.Mech. E.,
Chartered Patent Agent.