WO2006100192A1

WO2006100192A1 - Device for switching a electric circuit with a sequential opening system

Info

Publication number: WO2006100192A1
Application number: PCT/EP2006/060673
Authority: WO
Inventors: Sébastien CARCOUET; Laurent Chiesi; Henri Zara
Original assignee: Schneider Electric Industries Sas
Priority date: 2005-03-22
Filing date: 2006-03-14
Publication date: 2006-09-28
Also published as: FR2883658A1; FR2883658B1

Abstract

The invention relates to a device for switching an electric circuit in an electrical switch apparatus. The inventive device comprises a main switch (K'0) and two secondary switches (K'1, K'2) which are connected in series with an electrical load to be switched. The invention is characterised in that: the device comprises a first parallel-connected PTC-type resistor (R'1) of a first secondary switch (K'1) and a second parallel-connected NTC-type resistor (R'2) of a second secondary switch (K'2), and said device complies with a sequence for opening or closing the electric circuit between the switches. The invention also relates to a method of switching an electric circuit.

Description

Switching device for a sequential opening electric circuit

The present invention relates to a switching device of an electrical circuit in an electrical switch device and a switching method that can be implemented using such a device. The invention more particularly relates to a device and a switching method of an electrical circuit for avoiding arcing phenomena.

In order to preserve the contacts of a current switch and thus to increase the service life of the electrical device, it is known that when the current switch is opened or closed, is necessary to avoid the birth of an electric arc between the contacts. An electric arc inevitably occurs when both of the following conditions are met: - The value of the voltage across the switch is greater than that of the arcing voltage, and

the value of the intensity crossing the switch when it is opened or closed is greater than that of occurrence of an electric arc.

For example, when the switch contacts are gold, the arcing voltage value is 12 volts and the arcing intensity value is about 0.3. Ampere.

FIG. 1 represents the diagram of a protection circuit according to the prior art used in a switch electrical apparatus controlling the supply of an electric load by applying a voltage U _3Mm. According to this diagram, it is known to dispose of in parallel with a switch K "c controlling the power supply of the electric load a plurality of secondary switches IC ₁ , K" ₂ , .., K " _n in parallel and associate in series with each of these secondary switches a resistor R "i, R" ₂ , ..., R " _{n in} order to limit the phenomena of electric arc at the opening or closing of the electric circuit. The switch K " _o is used to ensure the galvanic isolation of the device. In such a protection scheme, the resistor R "iR" _n associated with each secondary switch K ¹ VK ¹¹ ,, must have a value to limit the intensity through the secondary switch K " _r K" _n when it opens or closing it to a value less than the appearance of an electric arc \ _aτc . The value of the equivalent resistance R _Θq to the resistors R "iR" _n arranged in the parallel branches must also be sufficient to limit the voltage across the switch K "c to a value less than the voltage of appearance of a Uarc electric arc when opened or closed.

In this prior art, the opening of the electrical circuit is thus achieved by first opening the switch K "c, the value of the voltage at its terminals being lower than the appearance of an electric arc \ J _aτc and then each of the secondary switches K " _r K" _{n is} controlled indifferently one after the other, the intensity of the current flowing through each of them having a lower value than the appearance of an electric arc U _o As for the closure of the electrical circuit, it is carried out by firstly closing each of the secondary switches K "rK" _n , the intensity of the current passing through them having a value less than that of the appearance of an electric arc U _c , and then closing lastly the switch K "c, the voltage at its terminals then being at a lower value than the appearance of an electric _arc U _arc - In such a protection circuit, the resistance associated with each of the secondary switches K" _r K " _n is s in order to limit the intensity to a value less than that of the appearance of an electric arc U _c and the value of the equivalent resistance R _eq to all the resistors in parallel must be sufficient to be able to fix the voltage across the terminals of the switch K "c to a value lower than the appearance of an electric arc \ J _aτc . Considering the resistance of the load R _Char g _e fed through such a protection circuit and by posing that the resistors R " _r R" _n have equal values, these conditions can be expressed by the following relations:

U bow. ^> ^ αlim

R n -4- J? eq ^Λ ch∞ge ^{^"*" Λ} eq

R "i ≥ ψ ± -R _Λut . ^R e _q - ~

The phenomenon of electric arc develops for example for a lare intensity equal to 0.3 amperes and a voltage U _ar c of 12 volts. In this case, it is deduced from the above relationships that, using a supply voltage of 220 volts and a load resistance of 110 ohms, the protection circuit must have 99 parallel branches each carrying a switch K "rK" _n and a resistor R "iR" _n in series to avoid arcing phenomena. This number is excessive and poses particular problems of size and cost.

The object of the invention is therefore to provide a limited size switching device that can be effective against arc phenomena.

This object is achieved by a switching device of an electrical circuit in an electrical switch device, said device comprising a main switch and two secondary switches characterized in that - the main switch and the secondary switches are connected in series with a electric charge to be switched,

a first PTC resistor is connected in parallel with a first secondary switch and a second NTC resistor is connected in parallel with a second secondary switch,

the device observes an opening sequence or a sequence of closing the electrical circuit between the switches.

According to a feature of the invention, during the opening sequence, the first secondary switch is opened first.

According to another feature, during the closing sequence, the first secondary switch is closed first and the main switch is closed simultaneously to it or immediately thereafter.

According to another particularity, the switches are microactuators that can be manufactured using MEMS type technologies or PCB or kapton PCB technologies. The object of the invention is also achieved by an electrical switch device adapted to switch an electric load between an open position and a closed position, said apparatus comprising a switching device as defined above for switching said load.

The object of the invention is also to propose a method of switching an electrical circuit that can be implemented by a switching device as defined above and comprising a main switch and two secondary switches. This process consists more particularly of: - connecting the main switch and the secondary switches in series with an electric charge to be switched,

connecting a resistor in parallel with each of the secondary switches, a first PTC resistor being connected in parallel with a first secondary switch, a second CTN resistor being connected in parallel with a second secondary switch.

- Open or close the electrical circuit respectively respecting an opening sequence or a closing sequence between the switches.

According to one particularity of the invention, the opening sequence comprises steps of:

opening of the first secondary switch, the value of the PTC resistor being sufficiently small so that the voltage across the first secondary switch is at a value lower than a threshold value,

- Opening of the second secondary switch and the main switch when the value of the PTC resistor has reached a value sufficient to limit the intensity of the current to a value below a threshold value.

According to another feature, the closure sequence comprises steps of:

- simultaneous closing of the first secondary switch and the main switch, - Closing the second secondary switch when the value of the NTC resistance has reached a sufficiently low value so that the voltage at its terminals is at a value below a threshold value.

According to another feature, the closing sequence can also be carried out as follows:

- closing of the first secondary switch followed by the closing of the main switch,

- Closing the second secondary switch when the value of the NTC resistance has reached a sufficiently low value so that the voltage at its terminals is at a value below a threshold value.

Other features and advantages will appear in the detailed description which follows with reference to an embodiment given by way of example and represented by the appended drawings in which: FIG. 1 represents, according to the prior art, a electrical switch with a protection circuit against arcing phenomena.

- Figure 2 shows an electrical switch device with a switching device according to a second embodiment of the invention.

FIG. 2 represents the switching device according to the invention. This device consists in associating two resistive components, a resistive component with a negative temperature coefficient (CTN or NTC) and a resistive component with a positive temperature coefficient (PTC or PTC). A PTC component has a low initial resistance that increases when a current flows through it. Conversely, a CTN component has a strong initial resistance which decreases when a current flows through it.

This type of component is well known in the prior art and its constitution is not the subject of the present invention.

According to the invention, the switching device controlling the supply of the load comprises a main switch K ' _o and two secondary switches K'i, K ' ₂ connected in series on the power supply circuit of the electric charge. The main switch K ' _o ensures the galvanic isolation of the device.

The PTC component is placed in parallel with the first secondary switch K'i, while the component CTN is placed in parallel with the second secondary switch K ₂ .

PTC and NTC components must meet the following specifications: the initial resistance of the PTC component must be low enough to ensure that the voltage across it is at a lower value than the appearance of an electric arc \ J _aτc. The PTC component is then in an on state.

the resistance of the PTC component when a certain amount of current passes through it must guarantee that the current flowing in the PTC component is limited to a value lower than the electric arc current _Δtc . The CTP component is then in a blocking state. the initial resistance of the CTN component must guarantee a limited or even no current flow. The CTN component is then in a blocking state.

- NTC component resistance when traversed by a certain amount of current must be sufficiently low to ensure that the voltage across it is at a value lower than that of appearance of an electric arc \ J _aτc. The CTN component is then in an on state.

When all switches are closed, the current flows mainly through the three switches in series. The PTC component has a low resistance (R <2 Ohms) and is therefore in an on state while the CTN component is at a high resistance (R> 1000 Ohms) and is therefore in a blocking state. The opening of the electric circuit is performed according to the following sequence:

- Opening of the first secondary switch KY The resistance of the PTC component being low, the voltage at its terminals is lower than that of appearance of an electric arc \ J _aτc . the current then passes through the branch of the circuit carrying the PTC component, which causes the PTC component to be heated and therefore the increase of its resistance. The current flowing in the PTC component is then limited to a value lower than the current of occurrence of an electric arc U _o

- Opening of the second secondary switch K ' ₂ and the main switch K' _o which are protected against the occurrence of an electric arc.

The opening of these two switches K ' _o , K' ₂ can be performed without respecting a specific sequence.

When closing the electrical circuit, no current flows in the electrical circuit, the electrical resistance of the PTC component is therefore low (R <2 Ohms) and the PTC component is then in an on state while the electrical resistance of the CTN component is high (R> 1000 Ohms), the CTN component then being in a blocking state. The closing of the electrical circuit is carried out according to the following sequence: - closing of the first secondary switch KV Closure of the main switch K ' _o simultaneous with that of the first secondary switch K'i or posterior thereto. The voltage at the terminals of the first secondary switch K \ is then at a value lower than that of occurrence of an electric arc \ J _arc and the current seen by the main switch K ' _o is at a value lower than the current of appearance of a Uo electric arc

- Once the first secondary switch K ^{^} ₁ and the main switch K ' _o closed, the current then passes through the CTN component which will heat up, causing a significant drop in its resistance and therefore the voltage at its terminals. . when the voltage at the terminals of the CTN component is at a value lower than that of the occurrence of an electric _arc , closing of the second secondary switch K ' ₂ which is thus protected against the appearance of an electric arc. According to an alternative embodiment, the main switch K ' _o may be closed prior to the first secondary switch KV However, in this situation, the closing of the first secondary switch K'i must take place immediately after and early enough for the components CTP and CTN have not changed of state under the action of the current flowing in the circuit. In other words, the desynchronization time between K ' _o and K \ must be less than the transition time of the CTP and CTN components to go from one state to another.

According to the invention, the KO-K ' ₂ switches used in the invention described above are, for example, microactuators that can be manufactured using MEMS type technologies or conventional PCB or kapton printed circuit technologies. These microactuators can be controlled for example by magnetic or electrostatic effect using for example a push-button type mechanism.

It is understood that one can, without departing from the scope of the invention, imagine other variants and refinements of detail and even consider the use of equivalent means.

Claims

1. Device for switching an electrical circuit in an electrical switch device, said device comprising a main switch (K ' _o ) and two secondary switches (K ¹ ₁ , K ₂ ) characterized in that,

- the main switch (K ' _o ) and the secondary switches (K'i, K' ₂ ) are connected in series with an electric charge to be switched,

a first PTC resistor (R'i) is connected in parallel with a first secondary switch (K ^{^} ₁ ), a second resistor (R ' ₂ ) of the CTN type is connected in parallel with a second switch (K ' ₂ ) secondary,

the device observes an opening sequence or a closing sequence of the electrical circuit between the switches (K ' _o , K'i, K' ₂ ).

2. Device according to claim 1, characterized in that, during the opening sequence, the first switch (IC ₁ ) secondary is opened first.

3. Device according to claim 1, characterized in that, during the closing sequence, the first switch (K ^{^} ₁ ) secondary is closed first and the main switch (K ' _o ) is closed simultaneously to it or immediately after this one.

4. Device according to one of claims 1 to 3, characterized in that the switches (K ' _o , K'i, K' ₂ ) are microactuators that can be manufactured using MEMS type technologies or printed circuit technologies in PCB or kapton.

5. Electric switch device for switching an electrical load between an open position and a closed position, characterized in that it comprises a switching device according to one of claims 1 to 4 for switching said load.

6. A method of switching an electrical circuit implemented by a switching device in a switch electrical apparatus, said device comprising a main switch (K ' _o ) and two secondary switches (K ¹ ₁ , K' ₂ ), characterized in that it consists of: - connect the main switch (K ' _o ) and the secondary switches (IC ₁ , K' ₂ ) in series with an electric charge to be switched,

- connect a resistor (R'i, R " ₂ ) in parallel with each of the secondary switches (K'i, K ₂ ), a first resistor (R'i) of CTP type being connected in parallel with a first secondary switch (K ^), a second resistor (R " ₂ ) CTN type being connected in parallel with a second secondary switch (K ' ₂ ).

- Making the opening or closing of the electrical circuit respectively respecting an opening sequence or a closing sequence between the switches (KOK'i, K ' ₂ ).

7. Method according to claim 6, characterized in that the opening sequence comprises steps of:

- Opening of the first secondary switch (K \), the value of the PTC resistor (R ₁ ) being low enough so that the voltage across the first secondary switch (K \) is at a value less than a threshold value (U _arc )

- opening of the second secondary switch (K ' ₂ ) and the main switch (K' _o ) when the value of the PTC resistor (R ' ₁ ) has reached a value sufficient to limit the intensity of the current to a lower value at a threshold value (U _c ) -

8. Method according to claim 6 or 7, characterized in that the closing sequence comprises steps of:

simultaneous closing of the first secondary switch (K 'i) and of the main switch (K' _o ),

closing the second secondary switch (K ' ₂ ) when the value of the resistance CTN (R' ₂ ) has reached a sufficiently low value so that the voltage at its terminals is at a value lower than a threshold value (U _ar c) -

9. Method according to claim 6 or 7, characterized in that the closing sequence comprises steps of:

- closing of the first secondary switch (IC ₁ ) followed by the closing of the main switch (K ' _o ), closing the second secondary switch (K " ₂ ) when the value of the resistance CTN (R ' ₂ ) has reached a sufficiently low value so that the voltage at its terminals is at a value lower than a threshold value (U _ar c) -

10. Method according to one of claims 6 to 9, characterized in that the voltage threshold value corresponds to that of appearance of an electric arc (U _arc ) and in that the threshold value of intensity corresponds to that of appearance of an electric arc (U _c ) -