Improvements in Electric Testing Apparatus.
Year: 1892

page_text: Date of Application, 9th Jan., 1892
.
Complete Specification Left, 8th Oct., 1892-Accepted, 12th Nov., 1892
. PROVISIONAL SPECIFICATION.
Improvements in Electric Testing Apparatus.
I, JAMES SWINBURNE, of Broom Hall Works, Teddington, Middlesex,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention has reference to apparatus for producing high electric pressures
especially such as are used for testing cables.
This
For instance, suppose it is required to test a cable with a capacity of a micro-
farad under 40,000 volts, a current of 10 amperes or so will be necessary.
might be supplied by a large dynamo capable of giving 400,000 watts and a
400,000 watt transformer, but this would be expensive. According to my invention
a comparatively small dynamo is used, capable of giving say, 10,000 or 20,000 watts,
and a transformer of the same output. In shunt to the cable I arrange a self
induction or choking coil which takes 10 amperes under 40,000 volts. This
choking coil is much cheaper to make than a transformer for 400,000 watts.
The choking coil is adjustable, so that it can be used to supply the capacity current
of any cable that may have to be tested. The transformers and choking coil are
preferably insulated with oil. Sometimes I prefer another arrangement. Suppose,
for instance that the dynamo can give 1000 volts, and 10 or 20 amperes, a choking
coil is arranged in series with it and adjusted so that its self induction exactly
neutralises the effect of the capacity of the cable. The outside of the cable is
earthed and so is one terminal of the dynamo, so that the dynamo does not need to
be made to stand high electric pressures. Such an arrangement as this will give,
say 100,000 volts and 10 amperes or so. A nargin must always be allowed, as the
self-induction does not exactly counterbalance the capacity, as the pressures do not
vary harmonically.
I am aware that it has been proposed, as an experiment to break down a
condenser by means of self-induction coil, but I am not aware that anyone has
proposed to use any such apparatus as that now described by me for commercial or
any practical purposes, such as testing cables.
Dated this 8th day of January 1892.
JAMES SWINBURNE.
COMPLETE SPECIFICATION.
Improvements in Electric Testing Apparatus.
I, JAMES SWINBURNE, of Broom Hall Works, Teddington, Middlesex,
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 has reference to apparatus for producing high electric pressures,
especially such as are used for testing cables.
For instance, suppose it is required to test a cable with a capacity of a micro-
farad under 40,000 volts, a current of 10 amperes or so will be necessary. This
might be supplied by a large dynamo capable of giving 400,000 watts & a
400,000 watt transformer, but this would be expensive.
According to my invention a comparatively small dynamo is used, capable of
giving say 10,000 or 20,000 watts, & a transformer of the same output. In shunt
to the cable I arrange a self induction or choking coil which takes 10 amperes
under 40,000 volts. This choking coil is much cheaper to make than a transformer
[Price 8d.1

page_text: for 40,000 watts. The choking coil is adjustable, so that it can be used to supply
the capacity current of any cable that may have, to be tested. The transformer &
choking coil are preferably insulated with oil. Sometimes I prefer another
arrangement. Suppose for instance that the dynamo can give 1,000 volts, & 10 or
20 amperes, a choking coil is arranged in series with it & adjusted so that its self
induction as nearly as possible neutralises the effect of the capacity of the cable.
The outside of the cable is earthed & so is one terminal of the dynamo, so that the
dynamo does not need to be made to stand high electric pressures. Such an
arrangement as this will give, say 100,000 volts & 10 amperes or so. A margin
must always be allowed, as the self induction does not exactly counterbalance the
capacity, as the pressures do not vary harmonically.
I am aware that it has been proposed as an experiment to break down a
condenser by means of self induction coils but I am not aware that anyone has
proposed to use any such apparatus as that now described by me for commercial or
any practical purposes, such as testing cables.
Having now particularly described & ascertained the nature of my said inven-
tion, & in what manner the same is to be performed, I declare that what I
claim is-
The application of artificial self induction to neutralise the effects of capacity in
testing electric conductors, substantially as described.
Dated this Seventh der of Antohan 1000
JAMES SWINBURNE.