Method of and Appliances for Regulating at Will the Power and Speed of an Alternate Current Motor.
Year: 1890

page_text: Date of Application, 2nd.Aug., 1890
Complete Specification Left, 16th Apr., 1891-Accepted, 11th July, 1891
PROVISIONAL SPECIFICATION.
Communicated from abroad by the firm of SIEMENS & HALSKE.. of 94, Mark-
grafen Strasse, Berlin, Germany, Electrical Engineers.]
Method of and Appliances for Regulating at Will the Power and
Speed of an Alternate Current Motor.
We, SIEMENS BROTHERS AND COMPANY LIMITED, of 12 Queen Anne's Gate,
Westminster, in the County of Middlesex, do hereby declare the nature of this
invention to be as follows:-
The alternate-current motors heretofore constructed are only equal in respect of
efficiency to continuous current motors so long as they run at a definite (synchro-
nous) speed. If this speed be departed from, the synchronous motor ceases to run,
while with a non-synchronous alternate current motor an amount of energy is
uselessly consumed which is in proportion to the deviation of the speed from
synchronism. If for example in working with variable speed with the existing
synchronous alternate current motors, it were desired to produce the great torque
required in starting at the said determined speed, the motor would have to be con-
structed of very large dimensions. If on the other hand the motor could at times
work usefully at a less speed and if at the same time its torque were correspondingly
increased, it would only be possible to develop the great torque required in starting
with a medium load.
This invention has for its object to attain this result. It consists in a method
which enables the speed and torque of an alternate current motor to be varied
inversely within certain limits.
The simplest means for regulating the speed of the armature, is to vary the
number of the active poles, and this is effected by varying the coupling of
the motoribobbins.
On the accompanying drawing this method is shewn carried out by way of
example in connection with an alternate current motor such as is described in the
Specification to Lake's (Tesla's) Patent No. 6481 of 1888. The method. mayıhow-
ever also be employed with other constructions of alternate current motors.
In the drawing A is the armature and R an iron ring built up of thinly divided
iron on which by way of example 12 bobbins are arranged. The ends of the
bobbins pass to 24 contact pieces mumbered from 1 to 24. The current.is supplied
through the four conductors P N and P N¹ connected to two rows of contacts I
and II.
If the 24 contact pieces are for instance, slid on to the row of contacts I there
are obtained in the ring R two rotating poles; if they are slid on to the row of
contacts II, four such poles will be obtained. With two poles the armature will
consequently make one half of a revolution during one change of polarity while
with 4 poles it will make one quarter of a revolution. The armature has con-
sequently with 2 poles its minimum torque, as it has its greatest speed, and the
product of torque and speed can be at most equal to the maximum quantity P H.
With four, poles, when it only requires to make half the number of revolutions, its
torque will be twice as great.
In the same way, with .a further row of contacts in connection with a suitable
number of exciting bobbins, the motor may receive 6. 8. 10 n poles with a simple
change of contacts, so that its synchronous speed will be proportioned. to that with
two poles as,
ኪ
to

page_text: sections as will produce with a certain combination of bobbins, the desired number
of poles.
The ring R can be provided with a continuous winding of the same direction
which for each row of contacts is divided into a suitable number of sections, in such
manner that each section is quite independent of the rest.
The coupling up of the bobbins can be effected by a coupler worked either by
hand or automatically.
Doted this and of Arount 1800
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Method of and Appliances for Regulating at Will the Power and
Speed of an Alternate Current Motor.
We, SIEMENS BROTHERS AND COMPANY LIMITED, of 12 Queen Anne's Gate,
Westminster, in the County of Middlesex, 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 :-
The alternate current motors heretofore constructed are only equal in respect of
efficiency to continuous current motors so long as they run at a definite (synchro-
nous) speed. If this speed be departed from, the synchronous motor ceases to run,
while, with a non-synchronous alternate current motor, an amount of energy is
uselessly consumed which is in proportion to the deviation of the speed from
synchronism. If for example in working with variable speed with the existing
synchronous alternate current motors, it were desired to produce the great torque
required in starting at the said determined speed, the motor would have to be con-
structed of very large dimensions. If on the other hand the motor could at times
work usefully at a less speed and if at the same time its torque were correspondingly
increased, it would only be possible to develop the great torque required in starting
with a medium load.
This invention has for its object to attain this result. It consists in a method
which enables the speed and torque of an alternate current motor to be varied
inversely within certain limits.
The simplest means for regulating the speed of the armature, is to vary the
number of the active poles, and this is effected by varying the coupling of
the motor bobbins.
On the drawing accompanying our Provisional Specification this method is
shewn carried out by way of example in connection with an alternate current motor
such as is described in the Specification to Lake's (Tesla's) Patent No. 6481
of 1888. The method may however also be employed with other constructions of
alternate current motors.
In the drawing A. is the armature and K an iron ring built up of thinly divided
iron on which, by way of example, 12 bobbins are arranged. The ends of the
bobbins pass to 24 contact pieces numbered from to 24. The current is supplied
through the four conductors P N and P N connected to two rows of contacts I
and II.
If the 24 contact pieces are, for instance, slid on to the row of contacts I there
are obtained in the ring R two rotating poles; if they are slid on to the row of
contacts II, six such poles will be obtained. With two poles the armature will
consequently make one half of a revolution during one change of polarity while
with 6 poles it will make one sixth of a revolution. The armature has consequently
with 2 poles its minimum torque, as it has its greatest speed, and the product of
torque and speed can be at most equal to the maximum horse power. With four
poles, when it only requires to make half the number of revolutions, its torque will
be twice as great.

page_text: In the same way, with a further row of contacts in connection with a suitable
number of exciting bobbins, the motor may receive 8, 10, n poles with a simple
change of contacts, so that its synchronous speed will be proportioned to that with
2
two poles as, to 1.
"
It is not necessary to provide the exciting ring with as many equal bobbin
sections as will produce with a certain combination of bobbins, the desired number
of poles.
The ring R can be provided with a continuous winding of the same direction
which for each row of contacts is divided into a suitable number of sections, in such
manner that each section is quite independent of the rest.
The coupling up of the bobbins can be effected by a coupler a simple form of
which is a cylinder with rows of contacts upon it, which can be turned to bring any
row into action.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The method of regulating the speed in synchronous alternate current motors
wherein the torque is increased simultaneously with a decrease of speed by varying
the number and distance apart of the active poles by means of a coupler, substan-
tially as described.
2. The use, for regulating the speed of synchronous alternate current motors as
set forth in the preceding claim, of coupling mechanism, in combination with a
series of exciting bobbins in such manner that a greater or less number of such
bobbins are rendered active in order to increase or decrease the number of polar
fields inversely to the speed of the machine.
Dated this 16th day of April 1891.
ABEL & IMRAY,
Agents for the Applicants.