Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates generally to the transformers,
and aims to provide a light weight, high rating transformer for
use in power-frequency circuits. One of the most important prob-
lems related with the construction of the transformers is con-
cerned with the removal of the heat generated by the power losses
of the transformer, without unduly increasing the weight of the
core and the space requirements of the transformer itself. The
said problem is even more of importance in the so called high
frequency power transformers for use for instance in arc welding
or resistance welding equipments.
SUMMARY OF THE INVENTION
In order to avoid the above and other disadvantages of
the prior art transformer, it is proposed according to the inven-
tion to provide a transformer in which each layer of both the
primary and the secondary windings of the transformer is wound on
radially spaced apart concentric tubular supports, whicn in turn
are mounted on a laminated iron core.
Between adjacent supports, air gaps are left, so as to
permit the flow of a cooling air stream.
Advantageously, the said cooling air stream is provided
by a fan associated with the transformer.
~ henever used as high frequency transformer, the said
transformer may be associated with a suitable inverter, from the
output of which the high frequency current is fed to the trans-
former. In this latter instance, the inverter may be disposed
between the transformer and the fan, in order to provide also for
the simultaneous cooling of the inverter.
Further objects and advantages of the invention will
become apparent from the following specification made with refer-
ence to the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure 1 is a side view of a transformer assembly accord-
ir.g to the invention, particularly suited for use as high fre-
quency transformer for welding equipment current, with associated
cooling fan and with the interposition between fan and transformer
of a block representing an inverter.
Figure 2 is a perspective view of the transformer of
Figure 1.
Figure 3 is a cross sectional view of the transformer of
Figure 2.
Figure 4 is the electric diagram of the inverter and
transformer of Figure 1, and
Figure 5 is a cross sectional view through a modified
embodiment of the supports for the primary and secondary windings
of a transformer according to the invention.
DESCRIPTION OF THE PREFERRED EM~ODIMENT OF THE INVENTION
With reference to Figures 1 to 3, the transformer shown
comprises a core 1, composed by a number of core sheets stacked
- 20 sheet by sheet to form the desired cross sectional area. The
core 1 has two outer legs 2, one middle leg 3 and two yokes 4
connected between the two outer legs 2 and the middle leg 3 at
both ends of the core.
Above the outer sheets of the outer legs 2 of the core
1, two pairs of U shaped longitudinal bars 5 are disposed. Each
pair of bars 5 are fastened together and to the core 1 by means
of bolts 6 which are passed through borings formed through one
leg of the bars 5 and through the outer legs 2 of the core. The
other legs of the bars 5 are provided with borings in which the
sleeves 7 made of electrical insulating material are inserted.
Through the sleeves 7 the bolts 8 are inserted. The bolts 8
projecting from the bottom end of the transformer may be used for
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fastening the transformer to a suitable support (not shown).
To the ends of the bolts 8 projecting from the top end
of the transformer two electrical conductive cross bars 9 are
secured. To each bar 9 a feed clamp 10 and a connecting link 11
are secured.
The supports 12 which in the example shown are in the
number of three are made of electric insulating material, and
for instance of ceramics material, and are spaced radially one
from another, so as to leave between them, as well as between
the innermost support and the middle leg 3, air gaps 17; Radially
extending assembling screws 14 are provided, extending through
the supports 12 in order to maintain the said supports in the
proper angular adjustment.
The said supports are further provided at their ends
with notches 13 for accomodation of the inner sides of the yokes
4.
On the outer mantle of the inner supports 12 the pri-
mary winding 15 of the transformer is wound, whilst on the outer
mantle of the outer support 12 the secondary winding 16 of the
transformer is wound. The terminals of the secondary winding 16
are clamped to the clamps 10.
A fan 18 is mounted in front of the supports 12, so as
to blow cooling air through the air gaps 17 of the transformer.
Between the fan 18 and the transformer, an inverter
circuit 19 is mounted.
As best shown in Figure 4, the said inverter circuit
comprises a rectifier 22, the input of which is connected to
the AC supply line 20. The output from the rectifier 22 is con-
nected through lines 23 and 24 to the input of the solid state
inverters 26 and 27. The inverters 26 and 27 may be for instance
of the kind manufactured and sold by Texas Instruments under the
denomination TIX H 809. 25 is a capacitor connected between
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lines 23 and 24. The outputs from the inverters 26 and 27 are
connected together in push-pull through lines 30, 31, the lines
30 and 31 being in turn connected to the input terminals 32 and
33 of the primary winding 17 of the transformer.
The two inverters are controlled by a suitable square
vave control frequency supplied through lines 28 and 29 by a
suitable source.
From the output of the two inverters 26 and 27 a square
vave AC current of the desired frequency is supplied to the input
of the transformer.
The operation of the described device will be evident.
Thanks to the feature that the single layers of both the primary
and secondary windings of the transformer are wound on separate
concentric tubular supports which are radially spaced apart one
from another by an air gap, a particularly efficient cooling of
the transformer may be achieved, thus increasing the rating of
the transformer, whilst decreasing its weight and space require-
ments.
Thanks to the above features, the transformer may be
used as power transformer for high frequency currents, up to
35,000 Hz.
More particularly, this transformer may be used as
power transformer for high frequency welding equipments which
must be operated with a high frequency current in the range of
500 to 20,000 Hz, and more particularly in the range from 3000
to 10,000 Hz.
DESCRIPTION OF A MODIFIED EMBODIMENT OF THE INVENTION
With reference to Figure 5, a modified embodiment of
the invention is shown. According to this embodiment, the tubu-
lar supports 12 for the layers of the primary and secondarywindings of the transformer are made of heat conductive metal,
and for instance of alluminium. The said metallic tubular
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supports are provided with a longitudinal split, in which a rod
34 of electric insulating material, and for instance of plastics,
is inserted. The said suppo.r~s are provided on their inner mantle
with radially inwardly projecting cooling fins 36, whilst on their
outer mantle there is provided a coating 35 of electrically in-
sulating material. Spacer means 37 made of electrically insulat-
ing material are fitted onto the ridge of some of the fins 36, so
as to avoid any contact between adjacent concentric supports 12.
