The invention moreover relates to a switch of the type containing an actuator which has two terminals, wherein an actuation voltage may be applied across the terminals to control connection or disconnection of a voltage to a terminal of a circuit by means of a movable contact spring to which the voltage is applied, and wherein the contact spring is adapted to assume a first position and a second position, said first position connecting the voltage of the contact spring to the circuit, said second position disconnecting the voltage of the contact spring to the circuit.

The invention finally relates to uses of the switch.

In an ordinary, available switch, a considerable part of the switch volume consists of necessary insulation dis- tances between the actuation coil of the switch and its current-carrying contact faces. This is necessary inter alia to obtain an insulation which protects the actuation coil and its terminals against possible voltage tran- sients.

In the development of switches, however, it is desired to make these smaller, and this could therefore be achieved inter alia if the above-mentioned insulation distance could be eliminated.

Accordingly, an object of the invention is to provide a method, wherein the insulation distance between an actua- tion part of a switch and its current-carrying contact faces may be removed, without voltage transients having a damaging effect.

The object of the invention is achieved by the method of the type defined in the introductory portion of claim 1, which is characterized in that upon connection to one or the other position the sum of the voltage to the circuit and the actuation voltage is applied to one terminal of the actuator, which actuation voltage may be positive, negative or 0, while the voltage to the circuit is ap- plied to the other terminal of the actuator.

It is hereby possible to apply to the switch a control voltage given by the voltage to the circuit plus or minus a DC voltage, which means that the voltage to the circuit and the control voltage do not have to be galvanically separated. Voltage transients that might occur will not affect the actuation voltage of the switch as it "follows" the voltage to the circuit.

As stated in claim 2, it is expedient that the voltage to the circuit is applied to both terminals of the actuator when the voltage to the circuit is disconnected.

As a safeguard against contact with the voltage to the circuit, a variant of the relay may generate the actua- tion voltage with a galvanic separation from the voltage to the circuit.

As mentioned, the invention also relates to a switch of the type mentioned in the introductory portion of claim 5.

This switch is characterized in that one terminal of the actuator has applied to it the same voltage potential as the contact spring.

The actuator voltage and the voltage potential are hereby applied to the same terminal in contrast to previous switches, in which the terminal of the actuator and the voltage-carrying terminal were separated physically from each other, which physical separation caused the switch to have a certain volume.

Expedient embodiments of the switch according to claim 5 are defined in claims 6-11.

As stated in claim 12, a control circuit is connected to the switch, said control circuit being fed by a single or a double voltage supply, which provides the voltage from one of the terminals of the switch to which the voltage to the circuit is applied, said control circuit providing the actuation voltage to the other terminal of the actua- tor.

The actuation voltage may hereby be built up in a simple manner by the control circuit, which may moreover be con- structed such that a galvanic separation is established inside the control circuit, thereby avoiding contact with high voltages.

In addition, as stated in claim 13, the switch may be adapted such that the supply voltage to the secondary side of a galvanic insulator integrated in the switch is applied between its terminals, said supply voltage being

applied by a voltage supply integrated in the switch and connected between the terminals of the switch or between one of the terminals of the switch and the connection terminal of the circuit, said galvanic insulator provid- ing the actuation voltage to the terminal of the actua- tor.

This provides a switch with four or more terminals which is extremely compact and is protected against the occur- rence of voltage transients through the actuator voltage.

As mentioned, the invention also concerns uses of the method and the switch according to the invention.

These uses are defined in claims 14-17.

In these uses it is possible to obtain remote control of the re-coupling of circuits which have been vitiated by a fault condition, e.g. by too great currents, or in which a fault current has been observed.

The invention will now be explained more fully below with reference to an embodiment shown in the drawing, in which fig. 1 shows the principles of the invention, fig. 2 shows the switch according to the invention con- nected to a control circuit, and fig. 3 shows the switch with an integrated galvanic sepa- ration.

In fig. 1, 7 designates a circuit which may be connected via its input terminals 3 and 10 to a voltage 2 that may be applied via a contact spring 4. The contact spring may be switched between two positions: position 1 and posi-

tion 2. In position 1, the voltage is disconnected from the circuit, while the voltage to the circuit 7 is con- nected in position 2. Furthermore, the figure shows an actuator 6, which may e.g. be an actuation coil adapted to switch the contact spring 4 between position 1 and po- sition 2. Upon application of a voltage on terminal 1 to terminal 8 on one terminal of the actuator, the switch will be able to switch the contact spring 4 between the positions 1 and 2. As will be seen, the other terminal 9 of the actuator is connected directly to the voltage to the circuit, so that when a voltage Vphase + Vact is ap- plied, the voltage difference between the terminals 1 and 9 will be Vact (Vact may have a positive or a negative value or be 0). If the switch is to disconnect the volt- age to the circuit 7, the voltage Vphase may be applied e.g. to the terminal 1 of the actuator, corresponding to Vact = 0, so that the voltage difference between the ter- minals of the actuator is zero. Alternatively, a voltage smaller than Vphase may be applied to terminal 1, which means that the contact spring 4 switches from position 2 to position 1. In this case, a symmetrical voltage about Phase is used as Vct. A so-called polarized relay is ob- tained hereby, as a positive voltage between terminal 1 and terminal 2 will connect the circuit 7, while a nega- tive voltage between terminal 1 and terminal 2 will dis- connect the voltage to the circuit 7.

In fig. 2 the actuator (in its entirety within the dashed quadrangle) according to fig. 1 is again shown in a set- up which includes a control circuit 16 to which voltage is applied via a voltage supply 12, which is in turn con- nected to Phase. A positive control voltage to the input 1 of the switch may be a fed from the voltage supply 12 to a terminal 13 on the control circuit 16, and this posi- tive control voltage may be passed further on to the ter- minal 8 on the actuator 6 for connection of voltage to

the circuit 7. The dashed line shows a connection to an input 19, which is used in the case where it is desired to have a double supply to the control circuit 16 and the actuator 6, to which a Vact, symmetrical about Vphac, is thereby applied, so that the actuator is constructed as a polarized switch.

Fig. 3 shows the switch as a unit (in its entirety within the dashed quadrangle) with a voltage supply 12 and an incorporated galvanic separation 11. The mode of opera- tion is the same as in the set-up according to fig. 2, as, here too, the voltage supply 12 may provide a double supply for the actuator 6.