Electricity: electrical systems and devices – Electric charge generating or conducting means – For application to living beings
Patent
1996-08-22
1998-06-23
Fleming, Fritz
Electricity: electrical systems and devices
Electric charge generating or conducting means
For application to living beings
256 10, 324510, 340649, H05C 104
Patent
active
057711470
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for testing the earth connection and measurement of the quality thereof for an electric fence energizer of the capacitor discharge type, in particular for determining whether the earth connection of the fence is defective. The energizer is principally a high voltage pulse generator and comprises in the conventional way a capacitor which is charged to a high voltage and is discharged to the primary winding of a transformer, the secondary winding of the transformer providing a very high voltage to an electric fence circuit.
2. Description of the Prior art
Electric fences conventionally comprise a bare electric conductor, one end of which, the proximate end, is connected to one output terminal of the electric fence energizer which provides, on its output terminals, high voltage pulses to the current conducting portion of the electric fence. The other output terminal of the energizer is connected to earth or grounded. The earth connection is conventionally made by the method that a pointed electrically conductive part, such as a metal part, an earth connection post, is inserted in the ground or soil close to the electric fence energizer as deeply as possible, preferably so deeply that a contact is obtained with humid layers in the ground. However, it is difficult to directly determine the quality of an earth connection and it will, in addition, vary depending on the weather and particularly on possible snow or rain. When the fence is heavily loaded, i.e. when the electrical resistance between the output terminals is low, a bad earth connection causes that the pulse from the electric fence energizer is applied over the earth connection instead of being applied over the fence, that is most of the output voltage is applied over the conducting path from the earth connection post to the ground surface area, where for instance an animal is standing, and a small part over the path from this ground surface area through the animal to the fence conductor, when the animal is in electrical contact with the fence conductor. The result thereof is a less performing or cancelled preventive or deterring effect of the electric fence.
A method for measuring the quality of the connection to earth is inserting a second earth connection post into the ground or soil at a place so far away from the first normal earth connection post that they do not influence each other. No significant current will then flow in the second earth connection post, and thus it is sufficient to use a second earth connection post having a simpler construction. During an electric fence pulse the voltage is measured from the normal earth connection of the electric fence device to this second earth connection post and if the voltage is too high, the earth connection is considered to be bad. This measurement is normally made by connecting a glow-discharge tube, which is arranged to be illuminated at the desired voltage difference between the earth connection posts. The disadvantages of this method are several: An extra earth connection post is required, this extra earth connection post must be connected correctly to earth and the signal does not consider the load from the fence, to which the energizer is subjected.
There is thus a need for methods and devices for determining the quality of the earth connection of an electric fence energizer, which do not require any extra steps performed by an operator, for instance without an extra earth connection post or without depressing some special key, but which can provide information directly on the quality of the earth connection in the electric fence energizer itself as fast as it is connected to its power supply and to the fence conductor and is started.
Various requirements from authorities restrict different characteristics of the electric voltage pulses which are allowed to be supplied to an electric fence. Such requirements can typically comprise that the pulses must not come more frequently than one pulse per seco
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Semko Certificate issued Apr. 15, 1987.
Eriksson Lars-Arne
Karlsson Goran Karl-Olov
Alfa Laval Agri AB
Fleming Fritz
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