METHOD OF MANUFACTURING A CAPACITOR ROLL, AND A CAPACITOR COMPRISING A ROLL THUS MANUFACTURED

METHODE DE FABRICATION DE CONDENSATEURS ENROULES ET CONDENSATEUR FABRIQUE DE CETTE FACON

English Abstract

ABSTRACT:

For the manufacture of capacitor rolls for
wound capacitors, the impregnation is performed by
subjecting the dielectric foils on their stock rolls
to an impregnating treatment in vacuum. The capacitors
manufactured from the capacitor rolls thus obtained
have a comparatively high breakdown voltage. The manu-
facture of the complete capacitor is no longer inter-
rupted for an impregnation treatment.


- 7 -

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of manufacturing a capacitor roll com-
prising the steps of:
- heating a stock roll of metallized dielectric foil
of synthetic material (without a moisture-absorb-
ing intermediate layer) in a vacuum container;
- reducing the pressure in said vacuum container;
- filling said vacuum container with a degassed
impregnating agent;
- exposing said metallized dielectric foil in said
vacuum container to said impregnating agent; and
- subsequently utilizing said metallized dielectric
foil to form a capacitor roll.
2. A method of manufacturing an impregnated die-
lectric foil for a capacitor roll comprising the steps of:
- heating a stock roll of synthetic dielectric foil
material without a moisture absorbing intermediate
layer, in a vacuum container;
reducing the pressure in said vacuum container;
- filling said vacuum container with a degassed
impregnating agent;
- exposing said synthetic dielectric material in said
vacuum container to said impregnating agent; and
- subsequently utilizing said dielectric material
wound with a metal foil to form a capacitor roll.
3. A method as defined in claim 1 or 2, where
said heating step takes place at a temperature of
between 50° and 60°C, said pressure is reduced to approx-




imately 0.01 Torr, and said dielectric foil is exposed
to said impregnating agent for at least 15 minutes.
4. A method as claimed in claim 1 or 2, wherein
said heating step takes place at a temperature of
between 50° and 60°C, said pressure is reduced to
approximately 0.01 Torr, and said dielectric foil is
exposed to said impregnating agent for a period of time
in the range of 20 to 30 minutes.

Description

PHD 76-029


The invention relates to a method of manufactur-
ing a capac;tor roll in which metallized dielectric foils
of synthetic material or metal foils together with dielectric
foils of synthetic material which are present on stock rolls
are wound without a moisture-absorbing intermediate layer,
in order to form a capacitor roll, the dielectric foils
being provided with an imprenating agent.
The following methods of impregnating foil
capacitors are known:
a) the capacitor rolls are impregnated ;n a vacuum contain-
er after winding. This method is comparatively time-
consuming, whilst, moreover, the manufacturing process of
the capacitors is interrupted;
b) it is known to provide the impregnating agent on both
sides oF the dielectric foils during w;nding. This can
be effected either by spraying or in a bath containing
an impregnating agent and wherethrough the foil is
transported. A method of impregnating of this kind
involves the risk of air being trapped between the
dielectric foil and the impregnating central layer,
which may cause reiects due to ionization. Moreover, it
is not simple to provide a comparatively thin layer
of i~pregnating agent according to this method:




.
- 2 -
.

i,. .

~La~8 9~ L PHD 76-029

c) it is known to impregnate a moisture-absorbing paper
strip which is processed, together with the dielectric
foils, to form a capacitor roll. The additional paper
layer, however, causes increased dimensions of the
capacitor roll.
The invention has fnr its object to perform
die/~c7L~jc
the impregnation of the ~We~e~trt foils during the
manufacture of capacitor rolls in a simple manner
without an additional moisture absorbing intermediate
layer and without the manufacturing process of the
complete capacitors to be manufactured from the rolls
thus obtained being adversely affected.
To this end, the invention is characterized
in that the dielectric foils are impregnated in vacuum
on their stock rolls.
The impregnation of the foils still present
on stock rolls is effected prior to the start of the
actual production of the capacitor roll. Asa result
of this vacuum impregnation treatment, a very thin
layer of imprenating agent without air inclusions is
obtained between the turns of the foil rolls. Con-
secutively, capacitor rolls are manufactured in the
usual manner from the foil rolls thus impregnated.
The invention will be described in detail
hereinafter with reference to a preferred embodiment.




:


~ .

1(~89~)4 ~ PHD . 7 6--O 2 9 .


The polyester foil rolls required for the
manufacture of polyester foil wound capacitors (two 8-/u
polyester foils and two 5-/u aluminium foils) are sub-
jected in the delivery condition, i.e. on the stock rolls,
to a heat tr~atment in an empty vacuum container for 10
to 20 minutes at a temperature of between 50C and 60C.
Meanwhile, the silicon oil to be used as the impregnat-
ing agent is degassed in a stock container in a vacuum
of 0.5 Torr. ConsecutiveIy, the foil rolls are evacuated
for 30 minutes to 0.01 Torr in the vacuum container. Sub-
sequently, the vacuum holder is filled with the previ-
ously degassed silicon oil. The stock rolls are removed ~;
from the impregnating bath after at least 15 minutes,
preferably 20 to 30 minutes.
The dielectric foils thus manufactured have
been used to form, in conjunction with metal foils, capa-
citor~rolls in the usual manner, and have been compared
with~capacitor rolls without impregnated polyester foils.
The breakdown strength of the capacitor rolls comprising
the polyester foil impregnated in accordance with the
invention amounted to 2430 V, whilst the breakdown
strength of the capacitor rolls comprising the non-
impregnated polyester foils amounted to 1725 V. The
breakdown strength~of corresponding capacitor rolls
having a non-impregnated 12-~u polyester foiI amounts
~to 2400 V. This aemonstrates that the 8-/u foils impreg-
; ~ nated by the method in accordance with the invention havs


~ '
4 ~:
~, ~ . '


~ . , - ,




PHD.-76~029.
19-1-1977.

the same breakdown strength as non-impregnated 12-/u foils.
~ Also the number.o~ weak spots (the number of
electrical breakdowns through the foils when a test vol-
tage of 1800 V is applied) of the dielectric foil is
substantially redueed by the impregnating treatment
in accordance with the inv0ntion. .
For example, silicon oil or wax can be used
as the impregnating agent. The dielec-tric foils can be
made of poIypropylene, polyester, polycarbonate or poly-
styrol. The dielectric foils may be metallized. Use can
alternatively be made of separate metal foils. Due to
the thinner i~termediate impregnating layer, the capa~
eitors manufaetured in accordance with the invention
: : have n higher capacitance relative to the capacitors
impregnated i~ aceordance with the kn!~wn methods, and
al~o show a substantial capacitance increase relative
to non-impregnated capacitors because, for example,
silicon oil has a dieleetrie eonstant o~ 2.5.l:~
Il .
- Ij

: '

7 : ' . 1

~: ` . '

~ ' ` ' . ; '
.


: ~: ' ' ' ,