NZ196469A

NZ196469A - Electric fence: pulse generator and power saving with full discharge when animal touches fence condutor

Info

Publication number: NZ196469A
Application number: NZ196469A
Authority: NZ
Inventors: W Weinreich
Original assignee: Horizont Geraetewerk
Priority date: 1980-03-14
Filing date: 1981-03-11
Publication date: 1984-05-31
Also published as: DE3167770D1; EP0036089A1; EP0036089B1; DE3009838C2; DE3009838A1; AU6834081A; ATE10892T1; CA1170708A

Abstract

1. A pulse generator, particularly for generating cattle-fence pulses, a) comprising a pulse transformer to the primary winding (W1 ) of which an electric charging capacitor (C1 ) and to the secondary winding (W2 ) of which an electric capacitor (Cz ; C2 + Cz ), for example an electrified fence which has an electric capacity, are connected, the electric capacity of the charging capacitor (C1 ) being considerably greater than the electric capacity of the capacitor (Cz ; C2 + Cz ) connected to the secondary side, the charging capacitor (C1 ) being constantly connected to a charging circuit (G1 ; G2 ) and, in the parallel circuit of charging capacitor (C1 ) and primary winding (W1 ) of the pulse transformer, a thyristor (Th), which is controlled by means of a pulse timer (T) for firing in a previously determined sequence in time, or a transistor which is provided with an external control arrangement, being inserted as a switch for generating an oscillation ; b) by corresponding development of the circuit arrangement and its electric components in the equivalent circuit, the inductance (L) and the leakage inductance (Ls) of the pulse transformer forming a coupled series- and parallel-tuned circuit with the capacities of the electric capacitors connected to the primary and secondary side of the pulse transformer, the series-tuned circuit of which coupled series-and parallel-tuned circuit contains the leakage inductance (Ls), the capacity which is effective at the secondary side, and resistive impedances, the electric values of which are given by the electric magnitudes of the pulse transformer and of the connected capacitors (C1 , C2 , Cz ), in which arrangement the closing of the switch in the parallel circuit of charging capacitor (C1 ) and primary winding (W1 ) of the pulse transformer and the discharge current which thus begins to flow are also accompanied by a transient event with a first sinusoidal transient current which flows via the series-tuned circuit and the switch and the frequency of which is determined by the leakage inductance (Ls) and the electric capacity which is effective in the series-tuned circuit and the damping of which is determined by the resistive impedances which are effective at the series-tuned circuit and, for the purpose of opening the parallel circuit consisting of charging capacitor (C1 ) and primary winding (W1 ) of the pulse transformer c.a) during operation without bypassing energy in the secondary circuit the transient event is used, in order to prevent energy losses, for cutting off the thyristor (Th) or transistor, with the charging capacitor (C1 ) being only partially discharged, whereas c.b) during operation including bypassing of energy in the secondary circuit, an increased damping, produced by adding a resistance (Rz ) of previously determined limit size on the secondary side, and the consequent adequate suppression of the negative half-wave (between pi 1 and 2pi 1 ) of the transient current is used for stopping the cutting-off of the thyristor or transistor by means of the transient event until the charging capacitor (C1 ) has been completely discharged, characterised in that the thyristor (Th) turn-off time and the pulse timer (T) firing pulse width or the phase relationships, which are analogous to the thyristor turn-off time and to the firing pulse width, of the signals supplied by the external-control arrangement to the transistor, are tuned to the electric values, determining the frequency of the transient event, of leakage inductance (Ls), capacity effective on the secondary side and resistive series impedance (R), in order to meet the following conditions : - that the triggering firing pulse, which makes the thyristor (Th) or transistor conductive, is shorter than the first positive half-wave (between O and pi 1 ) of the sinusoidal transient current, - that the thyristor or transistor, during a fully formed negative half-wave (between pi 1 and 2pi 1) of the sinusoidal transient current is cut off for the duration of this half-wave and - that, with the presence of a damping of previously determined magnitude in the series-tuned circuit, the negative half-wave (between pi 1 and 2pi 1 ), caused by this and at least partially suppressed, of the sinusoidal transient current is insufficient for the thyristor (Th) or transistor to be cut off or held in a cut-off state.

Description

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Patents Act, 1953 COMPLETE SPECIFICATION PULSE GENERATOR We, HORIZONT—GERATEWERK GmbH, a German company of Homburger Weg 4-6, D-3540 Korba'ch 1, Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us f and the method by which it is to be performed, to be particularly described in and by the following statement 1 96 4 6 9 The invention relates to a pulse generator, in particular for generating fence pulses and having a pulse transformer of which the inductances and leakage inductances form, together with an electrical charging capacitor connected to the primary side and an electrical capacitor connected to the secondary side, for example a fence capacitance, a coupled series and parallel oscillator circuit, and having incorporated into the parallel switching circuit of primary winding of the pulse transformer and charging capacitor a thyristor controlled by a pulse timer to fire in a predetermined time sequence or a transistor with remote control facility to act as a switch, the charging capacitor being constantly connected to a charging current circuit and the capacitance of the charging capacitor being substantially greater than the capacitance of the capacitor connected to the secondary side.

Where pulse generators of this type are concerned, the pulse to be generated and applied for example to an electric fence originates as a result of the electrical oscillation initiated upon closure of the parallel current circuit of primary winding and charging capacitor and transformation of this oscillation to a high voltage in the pulse transformer. Prior art units of this type are so dimensioned that the thyristor is blocked by the negative half-wave of that oscillation which is determined by parallel inductance in 196460 the coupled series and parallel oscillating circuit and the ♦ capacitance of the charging capacitor. This means that the thyristor is blocked by the negative half-wave of the current in the second periodic oscillation, i.e. the main oscillation.

Since however, in the coupled series and parallel oscillating circuit, the voltage of the oscillation leads the current of the oscillation by tt, at the moment of blocking of the 2 thyristor, the charging capacitor is already charged with a polarity reversed to what it was originally. For the next pulse from the current source, therefore, it must be discharged and charged with reverse polarity. r- Ok* \&- P«*.Vr——> *2001^97^ \ftprmrin Offonlogungooohrift Ho^—27 33 145 has already proposed that the switching element in the primary circuit, i.e. the parallel current circuit of charging capacitor and primary winding of the pulse transformer, be opened when the series capacitance has been charged up to or close to the upper peak value of the transient voltage. In practice, however, it has been demonstrated that this method of controlling the switching element is very sensitive and can only be carried out with difficulty.

In contrast, it is the object of the invention to provide an improved circuit arrangement in which the switching element in the parallel current circuit of charging capacitor and primary winding of pulse transformer is reliably blocked at some predeterminable and reproducible point in time or N.Z. PA'.T^iTT OFFICE 2 3 NOV 1983 RECEIVED opens this parallel current circuit as soon as sufficient energy has been drawn from the charging capacitor for a desired pulse, for example a pulse which is to be applied to an electric fence.

According to the invention, this problem is resolved in that the thyristor in respect of its recovery time and the pulse timer in respect of the width of the trigger pulse for, analogous with the recovery time of the thyristor and the width of the trigger pulse, the phase positions of the signals given to the transistor by the remote control element, are so attuned to the electrical values of leakage inductance, effective capacitance on the secondary side and ohmic series resistance as determined by the electrical magnitudes of the pulse transformer and of the connected capacitors provided in the coupled series-parallel circuit and by the first sine-wave current arising upon closure of the parallel circuit of charging capacitor and primary winding of the pulse transformer, that the first negative half-wave (between tt^ and 2tt^) of the sine-wave current blocks the thyristor or the transistor and the triggering pulse which renders the thyristor or the transistor conductive, is shorter than the first positive half-wave (between 0 and tt^) of this sine-wave current, this attuning being however so contrived that a damping occasioned by cutting in a previously established resistance on the secondary side suppresses the negative 1 964 6 9 half-wave (between and 2ir^)' of the current of the first sinusoidal oscillation sufficiently for it no longer to block the thyristor or the transistor.

The invention provides two essential advantages: avoidance of losses and increased shock effect in electric fences. Both results constitute substantial improvements in electric fence technology.

In a particularly advantageous embodiment of the invention, it is possible to connect in parallel with the secondary winding of the pulse transformer a fixed capacitor which is parallel with the fence capacitance, one or a plurality of diodes being incorporated into one or both connecting lines between this fixed capacitor and the fence capacitance.

In the event of a transistor being used as the switch, the remote control of the transistor may be equipped with means of attunement to the length or capacitance of the electric fence.

Embodiments of the invention will be described in greater detail hereinafter with reference to the accompanying drawings, in which: Figure 1 shows the principle of the circuitry in the pulse generator according to the invention which can be fed alternatively from a direct current voltage source or from an alternating current voltage source, 'U Figure 2 shows the pulse generator according to Figure 1 with the equivalent substitute circuit diagram of its pulse transformer, Figure 3 shows a modified embodiment of the pulse generator according to Figure 1 in which the electric fence is coupled via a diode and wherein a fixed capacitor is applied parallel with the secondary winding of the pulse transformer, and Figure 4 shows the principle of the time-related pattern of the current through the thyristor during a pulse process in the case of equipment representing the state of the art.

In the view in Figure 1, and W2 are the primary winding and the secondary winding of a pulse transformer T?r with the associated inductances L, and L_. L , and L „ are 1 2 si s2 the relevant leakage inductances which usually amount to a few percent of the particular main inductance concerned. and R2 are the ohmic winding and line resistances. is a - preferably large - charging capacitor which - as illustrated -is connected to the primary winding via the thyristor Th. The charging capacitor is charged to a voltage U^, in fact via an upstream series-connected diode D^, from a direct current voltage source which may for example be a DC-DC converter G2 or an alternating current voltage source equipped with a rectifier. 1 96 4 6 9 Connected in parallel with the secondary winding of the pulse transformer Tr is a capacitance C which is preferably z intended to represent the capacitance of a fence wire in respect of the earth. This capacitance Ccan however, in another application, also be a fixed capacitor or the like. Rz is an ohmic resistance which is for example cut in when an animal touches the fence wire, energy being consumed via this resistance (or animal's body).

T is a per se known pulse timer which preferably at intervals of approximately 1 second to 2 seconds emits a brief trigger pulse to the grid of the thyristor Th and renders it conductive, the timer preferably being fed directly from the relevant voltage source.

Figure 2 shows the electrical layout diagram corresponding to the pulse generator according to Figure 1. L is the equivalent replacement inductance of the pulse transformer, Lg is the equivalent inductance of the leakage inductance and R is the equivalent resistance. The pulse transformer has as a rule a transformation ratio in which W2 is greater than W^. All values in the equivalent circuit diagram relate either to the primary side or to the secondary side.

Let it be assumed that the charging capacitor C^ is charged to voltage . A trigger pulse renders the thyristor Th conductive. As a result, the charging capacitor C^ is switched to the pulse transformer. The equivalent inductance | 0/£v A L is large in comparison with the equivalent leakage inductance L , so that the impedance of the path L , R, C is substantially s s z smaller than that of the path via L. As Figure 4 shows, initially a damped sine-wave current flows, determined by the angular magnitudes of the first path, and has an angular frequency of By reason of the small values of Lg in comparison with L and of Cin comparison with C^, the frequency of this first oscillation is high. When this oscillation, known as a building-up transient oscillation, has elapsed, the current merges into a second oscillation which is determined by the capacitance of the charging capacitor C^, the equivalent inductance L of the pulse transformer and the equivalent resistance R. The angular frequency °f this second oscillation is therefore substan-| tially smaller than the angular frequency of the first oscillation.

Before the thryistor Th becomes conductive, a definite amount of electrical energy is stored in the charging capacitor 2 (1/2C^ * ). If the thryistor Th is triggered and is blocked only as of the moment in time tt^, as occurs according to the state of the art, then the energy swings between the charging capacitor and the equivalent inductance L of the pulse transformer. The charging capacitor discharges fully and there is built up in the inductance L an equivalent 2 magnetic energy (1/2 LI ) which in turn flows back to the charging capacitor as capacitive energy - but with reversed polarity. At point in time itthe changing capacitor -with deduction of the losses - is charged again with reverse polarity. The current through the thyristor Th is now negative and the thyristor blocks. By reason of the now reversed polarity of the energy in the charging capacitor C^, the diode is now conductive and the energy flows out and becomes equalised in the upstream power supply, e.g. in the mains. The energy is lost and does not come back. The charging capacitor must now be charged again. This process is repeated.

In the case of a well-insulated fence - when only the fence capacitance Cz is cut in - only a small part of the energy (in R) is consumed in the pulse generator and in the connected fence. The main part of the energy is lost due to I reversal of the polarity and the resultant discharge of the charging capacitor via the power supply.

If a fence discharge resistance Rz (for example contact with an animal) is cut in, then the energy flows out of the charging capacitor fully or partially, according to the size of the resistance Rz directly into this consumer and is here usefully converted (for example into a shock effect). At the point in time ir2, this process has already elapsed. No or only very little energy flows back to the charging capacitor C^. 1 96 4 6 As a rule, an electric fence is well insulated. Contact with an animal occurs only very rarely and therefore has no noticeable influence on the overall energy balance of the electric fence equipment.

The energy taken from the current source per pulse must be written off as lost energy in the case of conventional units. In the case of equipment operated from the electricity supply mains, this is tolerable, because this amount of energy is only very small even in the case of powerful units. This waste of energy does however become important in the case of battery-operated equipment, which represents as much as 80% of the equipment in practical use. Such units are operated from special dry batteries which are relatively expensive. As stated above, this expensive energy is almost completely converted into pure loss energy.

A basic remedy is provided according to the invention if the thyristor is blocked already at the negative half-wave of the first sinusoidal operation to 2tt^) . By this point in time, only as much energy will have flowed out of the charging capacitor C^ as is required to charge the fence capacitance C^. The fence capacitance Cz is as a rule small in comparison with the capacitance of the charging capacitor C^, so that the major part of the energy remains unchanged in the charging capacitor C^. 1 96 4 6 9 According to the invention, therefore, the values of leakage inductance L , equivalent resistance R and the s « secondary-side capacitance, i.e. a fixed capacitor C^ connected to the fence capacitance Cz or in parallel with the secondary winding of the pulse transformer, as well as the recovery time of the thyristor Th are so selected that the thyristor is blocked by the negative half-wave of the first oscillation to 2tt^) . At the same time, though, the trigger pulse must have elapsed already at ir^ so that the trigger pulse does not keep the thyristor open. The process of discharging the charging capacitor is interrupted again. Then, only as much energy is taken from the charging capacitor as is required to charge the secondary-side capacitanc.e, whether it be a parallel-connected fixed capacitor C„ or the fence capacitance C . The energy given off thereby ^ z by the charging capacitor is additionally supplied by the upstream energy source.

In the event of animal contact, a discharge resistance R is cut in in parallel with the fence capacitance C . z z This leads to a marked damping of the first oscillation, the second half-wave of the first oscillation between and 27becoming substantially smaller or no longer appearing.

The thyristor Th is now no longer blocked. The energy of the charging capacitor now discharges itself fully via the connected resistance R or the body of the animal, this z 1 964 6 9 energy or a part thereof generating an effect of pain due to muscle contraction.

In the case of the above-explained attuning and construction of the circuit arrangement according to Figures 1 and 2, in accordance with the invention, normally the charge applied to the fence capacitance Cis discharged again via the upstream inductance, so that also this amount of energy is lost. If in the case of very long electric fences the fence capacitance Cnevertheless assumes a considerable level, then in a modified embodiment shown in Figure 3 the flow-back of this energy can be prevented by incorporating a diode • In this case, for practical purposes, there is no further energy loss. However, in this case it is necessary to provide a fixed capacitor so that the first sinusoidal oscillation can form. The capacitance of this fixed capacitor C2 may be small in comparison with the capacitance of the charging capacitor so that also the losses which are unavoidable can be kept small by this fixed capacitor C2> 1 96469

Claims

WHAT WE CLAIM IS: J.. An electric fence comprising in combination; a) a fence conductor, bl a circuitry including a transforming, voltage-multiplying inductive device, and a charging capacitor connected to said transforming device, and means connecting said charging capacitor for continuous energization from a voltage source, said circuitry having terminals connected respectively to the fence conductor and to a ground; c) said circuitry comprising a parallel resonant circuit having a primary coil of said inductive device containing inductance and ohroic resistance of said device, the said charging capacitor and a controllable electronic switching deyice, wherein said primary coil and said charging capacitor are connected in parallel and said switching device is connected in series between said primary coil and said charging capacitor; d) said circuitry comprising a series resonant circuit which includes the said charging capacitor, a fence capacitance occurring between said fence conductor and the ground, leakage inductance occurring in said device, the ohmic resistance of said inductive device and said conductor, and said controllable electronic switching device, all connected in series, and a further resistance connectable in parallel with said fence capacitor; e) said electronic switching device having a control electrode to which control signals may be applied, and having control means for holding said switching device in switched-on condition as long as an electrical current flows through said switching device in the one direction, whereby the switching device in response to repetitious impulses applied to its control electrode, can rapidly switch on to allow current to discharge the charging capacitor and to flow within the parallel resonant circuit; - 13 - W.2. PAT2NV OrFICE -2FEB1984 r.PCEIVED 196469 f) said series resonant circuit having a predetermined resonant frequency which, is so related to the said switched on holding control .means of said switching device that the second half-wave of a transient current in the series resonant circuit occurring when the switching device is switched on at a point of time within the second half period of said transient current will result in the switching device turning off to interrupt the current discharging of said charging capacitor, wherein an animal contacting said fence conductor presents said further resistance connected in parallel with said fence capacitance which damps said transient current so that the switching device is not turned off and said charging capacitor discharges through said animal.
2. The electric fence as defined in claim 1, wherein said switching device is a thyristor which is converted into its conductive state by applying a firing signal into its control electrode, and wherein said switched on holding control means of the thyristor includes the holding current characteristics and the turn-off-time characteristics of the thyristor itself, by which the thyristor automatically converts into its non-conductive state during the negative half-wave of the transient current.
3. The electric fence as defined in claim 1, wherein said switching device is a transistor which is converted into its conductive state and non-conductive state respectively by control signals applied to its control electrode, and wherein the switched-on holding control means of the transistor is a separate control facility which is adapted to convert the transistor into its non-conductive state during the negative half-wave of the transient current by means of a control signal. . — : I;i>-OFFICE - ,14 - ; — i -2FEB1984 DECEIVED 1 964-69
4. The electric fence as defined in claim -1, wherein the inductance in the series resonant circuit is substantially less than the value of the inductance in the parallel resonant circuit.
5. The electric fence as defined in claim 1, and further including a second capacitor which is connected between the ground and the terminal connected to the fence conductor.
6. The electric fence as defined in claim 5, wherein the second capacitor has a capacitance equivalent to said electric fence capacitance.
7. The electric fence as defined in claim 1, wherein the means connecting the charging capacitor for continuous energization from a voltage source is exclusive of said inductive device. wtv
8. The electric fence as defined in claim^^" wherein: a) the inductive device comprises a pulse transformer having primary and secondary windings, b) the inductance of said parallel resonant circuit includes the primary winding of the transformer, c) a pulse timer is connected to the control electrode of the thyristor to switch the latter on at fixed time intervals, d) said secondary winding of the transformer is connected to said fence conductor and the ground, e) said pulse transformer has a smaller leakage inductance than its winding inductance, f) said parallel resonant circuit has an appreciably lower oscillation frequency than that of the series resonant circuity • '.i::: office - 15 - i ~~ -2FEB1984 IECEIVED 1SG469 g) said thyristor is characterized by a holding current which is apparently smaller than the initial descharge current of said charging capacitor, such initial discharge current building up to sine-shaped positive half-wave in the series resonant circuit, h) said thyristor has a turn-off-time which is shorter than the oscillation frequency half-period in the series resonant circuit, and i) said pulse timer has a pulse length in time of the firing pulse given by it to the thyristor which is shorter than said oscillation frequency half-period of the series resonant circuit. HORIZONT-GERATEWERK GmbH By Their Attorneys :ted 2 3 NOV 1983 16