Today many research activities on the next generation switching apparatus are directed to and involve the use of drives based on Thomson coil or repulsive drive.

This kind of drive is simply based on a fixed part made of a coil and a moving part, made of solid metal, which is close to said fixed part. When the fixed part, i. e. the coil, is run through by a fast rising current, it generates strong eddy currents in the close moving part. Then, the coil current and the eddy current develop a force impulse between fixed and movable part, causing the movable part to move in a time which is of the order of hundred of microsecond.

The speed of this kind of drives is more than two orders of magnitude faster than the present mechanical drives which are used for the today circuit breaker. This feature will allow to develop a new generation of switching devices, with higher characteristics and performances and lower cost.

A schematic view of this kind of solution, as presently known in the art, is given in figure 1.

The present state of the art of the electronic control for repulsive drive requires big and expensive power electronic components in order to switch-on the circuit and discharge, inside the drive coil, the energy accumulated within a capacitor bank. These power electronic components are normally designed for continuous currents, flowing for several ten years; they are therefore very limitedly exploited in this kind of application, i. e. to control repulsive drives, in which the component is switched-on for a maximum of only a few thousand times, for some hundred microsecond each time.

On the other side it is not possible to reduce the size of the electronic components below a certain limit, since the components themselves must be

able to withstand the very high peak currents, which are normally necessary for the functionality of the repulsion drive.

The goal of the present invention is to substitute the power electronic component used to switch on the current in the drive coil with a simpler device, having low cost components, but at the same time being able to perform all the functions needed by the drive coil. This goal is achieved, according to the present invention by using components, which are normally used to discharge voltage transient in order to protect electronic circuit.

This is in reality only one of the potential application of the circuit of the present invention, since basically all applications in which there is a power electronic component being switched on, could be substituted with a gas discharge arrangement in the way as described and claimed in the present invention. The circuit of the present invention is preferably applied to high current, switch-on electronic components without continuous duty. In figure 2 is represented a generic electronic circuit used to transfer power form a power supply to a load through a switch-on component.

According to the present invention, two gas discharge voltage suppressors, or one having three pins, can be used instead of the single power electronic switch.

The gas discharge voltage suppressors are dimensioned in order to be able to withstand the foreseen current to be let through for a number of requested time; the characteristics and the dimensioning can be determined by taking as reference the manufacturer data-sheet.

Furthermore, the voltage of the discharge voltage suppressors is chosen in such a way that the two components in series can easily withstand the nominal voltage at which the capacitor bank is charged, while this is not anymore valid once one component is short-circuited by a suitable control circuit, letting the other being naturally ignited by a voltage higher than the its own nominal voltage.

By applying the circuit as described in the present invention the cost of the

repulsive control drive can be reduce in a considerable way.

The same conclusion is applicable to and can be extended to all applications where there is a power electronic component being switched on; such power electronic component can be substituted with a gas discharge arrangement in the way being described in the text and in the drawings of the present invention.

In particular: Figure 3 represents a schematic electronic circuit, showing a first possible embodiment of how to apply the gas discharge overvoltage suppressor components according to the present invention; Figure 4 represents a schematic electronic circuit showing a further possible embodiment of the solution according to the present invention, with gas discharge components to supply generic loads through a switch-on component; Figure 5 represents a schematic electronic circuit showing a further possible embodiment of the solution according to the present invention, with a three pins Gas Discharge component to supply generic loads through a switch- on component.

As already said and as shown in the accompanying figures, either two or only one gas discharge voltage suppressors used can be.

When a single gas discharge voltage suppressor is used, a three pins component needs to be used. In such a case, the intermediate connection is used to control the switch-on operation.

The application of the circuit according to the present invention to a drive coil is only one of the possible application of the present invention; the basic idea can be applied to all electronic circuit in which use of power electronic switched-on component is made, the said power electronic switched-on component being possibly substituted by gas discharge voltage suppressor devices.

There are however some limitation about the possible use of the circuit of the present invention as substitute of power electronic switched-on components.

Particular care must be taken for instance in the following cases, in which

additional features might be necessary in order to have proper functionality of the system. In particular: the switch-on operations are not followed by a switch-off operation until the voltage operation has gone down to zero, or a switch-off support circuit is used, like for instance those used for tyristors. the switch-on operation should not be repeated too often, in order not to reduce the life of the gas discharge voltage suppressor, below the expected period. the precision of voltage intervention of this gas discharge component is not very high, so adequate tolerance in dimensioning has to be taken.

The high current controlled switch-on circuit according to the present invention allows to achieve the intended goals and objects.

In particular, the low cost gas discharge voltage suppressors used in the circuit according to the present invention allow to control operation of repulsive drive in an effective way, without any need to use expensive power electronic components.