Improvements in Cooling Appliances for Alternating Current and Rotary Phase Current Motors.
Year: 1899

page_text: Date of Application, 5th Jan., 1899-Accepted, 11th Mar., 1899
Improvements in Cooling Appliances for Alternating Current and
Rotary Phase Current Motors.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, Westminster,
in the County of London, Electrical Engineers, do hereby declare the nature of
this invention (as communicated to us from abroad by Siemens & Halske Aktion
Gesellschaft, of Markgrafen Strasse 94, Berlin, S.W., Electrical Engineers),
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
-
In alternating current or rotary phase current motors there are often provided
in the rotor, for the purposes of effectual cooling by air currents, one or more
slits or channels arranged at right angles to the axis, and also openings near the
axis and parallel thereto. By means of the centrifugal action set up in the said.
slit or slits, the air is drawn in through the openings parallel with the axis,
and is expelled through the narrow annular space between the rotor and stator,"
so that in coming in contact with extended surfaces the air currents have a cooling
effect thereon. It has been found that unless special preventive means be em-
ployed a portion of the warmed air issuing at both ends of the annular space
between rotor and stator is again drawn in through the said openings near the
axis, and thus the intended useful effect of the arrangement is to a great extent.
neutralised. It is also very desirable to utilise the outer surface of the stator.
iron for increasing the cooling effect, and also, for the same purpose, to cause
the cool circulating air to come in close contact with the bends or the connecting
pieces of the windings situated at the end surfaces of the stator and rotor.
The present invention relates to appliances to such motors for accomplishing.
the above named purposes which we will describe with reference to the accom-
panying drawings, in which Fig. 1 shews a longitudinal section of a motor with
the said improvements applied thereto, Fig. 2 shews a part end view and part
cross section, and Fig. 3 shews a modification. The stator S, constructed in the
known manner of sheet iron with grooves for the winding is carried by ribs RR
on the inner side of the casing G, so that between the latter and the stator
there is an annular space which communicates by means of opening O with the
outer air.
The rotor has parallel to its axis, the central passages LL, and in the middle
of its length the slit T communicating with those passages and formed by the
distance pieces Z Z Fig. 2.
At the left hand end face of the rotor are fixed fan blades F F (assuming the
winding to be of the bar kind with end connecting loops) while at the right
hand end, which is shewn with wire windings the end loops together with the
protecting ring P constitute a fan.
Lastly there are provided inside the end covers D D guiding shields B B
which are formed so as to approach near to the fan blades For the ring P and
have a central hole of such a size as to leave an annular opening round the axis.
In place of the guiding shields being formed separate from the casing they
might of course be formed in one therewith.

page_text: On the rotation of the rotor the air will be drawn in through the annular
openings of B by the centrifugal action of the fan blades or their equivalents at
the end surfaces and of the middle slit T and a portion will pass radially outwards
into the space between the shields B and the end surfaces of the rotor and
stator, being thereby brought into close contact with the end loops or connecting
pieces of the windings, and after passing thence over the outer periphery of the
stator winding the air will eventually escape into the atmosphere through the
openings 0 0.
Another portion of the entering air will, on the other hand after being drawn
through the longitudinal channels L of the rotor into the middle slit and on
being propelled radially outward through this will then pass along the narrow
annular space between the rotor and stator to the ends of these, where it will
mix with the before described portion of the air passing
at such ends and
will escape together with the same through the openings O
as
By thus causing the air to escape at a point as far distant as possible from the
points of inlet it is brought to the greatest possible extent in contact with parts
of the motor that require to be cooled and any return of the warmed air to the
points of entrance again, such as was previously referred to, is effectually pre-
vented.
In some cases we dispense with the fan-like action at the end surfaces of the
rotor by forming the shields B as shewn at Fig. 3 where they are brought close
against the said end surfaces and thus serve to prevent any of the warmed air
from being drawn back to the passages L L.
Having now particularly described and ascertained the nature of this
invention, and in what manner the same is to be performed, we declare that
what we claim is:-
1. In alternating current or rotary phase current motors the combination with
the end surfaces of the motor casing of guiding shields arranged to operate in
conjunction with fan blades or equivalent devices at the end surfaces of the rotor
so as to produce currents of air directed radially outwards from the central air
inlets, which currents have the effect both of cooling the parts of the windings
with which they are brought into contact, and of preventing the warmed air that
has passed through the ventilating channels of the rotor from being drawn back
to the central inlet, substantially as described.
2. The arrangements of shields such as are referred to in the first claim in
such manner as to fit close against the end surfaces of the rotor in order to prevent
the warmed air that has passed through the ventilating channels from being drawn
back to the central air inlets, substantially as described.
Dated this 5th day of January 1899