CN100372039C

CN100372039C - Electric switch power supply

Info

Publication number: CN100372039C
Application number: CNB038226006A
Authority: CN
Inventors: 奥利·萨洛宁; 马尔蒂·赛拉宁
Original assignee: Schneider Electric SE
Current assignee: Schneider Electric SE
Priority date: 2002-09-23
Filing date: 2003-09-23
Publication date: 2008-02-27
Anticipated expiration: 2023-09-23
Also published as: NO328490B1; EP1547110A1; WO2004027807A1; AU2003262614A1; AU2003262614B2; PL206414B1; NO20052005L; PL375739A1; RU2316074C2; RU2005111544A; FI20021692A0; FI113502B; CN1685458A

Abstract

The invention relates to a method for realizing power supply into an electric switch (1), and a respective power supply arrangement for an electric switch. The switch is arranged in the current path (J), between an AC current source (E), preferably an AC current mains, and a load (L) in order to interrupt and enable power supply. The switch is also arranged in series with the primary circuit (W1) of a current transformer (3). The electric power required by the control unit (2) of the switch an possibly of the switch itself is taken over the switch when the switch is on (a) and from the secondary circuit (W2) of the current transformer via a rectifier (4), when the switch is off and power is fed to the load (L). According to the invention, the current transformer (3) is arranged to function so that it is saturated at each halfcycle of the mains current, and the saturation peaks (KP) of the secondary voltage (W2; W2a; W2b) of the secondary circuit of the current transformer are rectified in order to obtain direct electric power, when the switch (1) is off (k).

Description

Method for supplying power to an electric switch and power supply arrangement for an electric switch

Technical Field

The invention relates to a method for supplying power to an electric switch between an alternating current source and a load. The invention also relates to a power supply arrangement for implementing an electric switch between an ac power supply and a load.

Background

The electrical switch in this application is an electromechanical switch, e.g. a relay switch, a semiconductor switch, and/or combinations thereof, such as a parallel combination of a relay switch and a semiconductor switch, e.g. a triac. Switches of this type are used for switching on and off electrical devices, in particular lighting devices, connected to an alternating current source, for example an alternating current network, which electrical devices are controlled by, for example, timers, dual-light switches or moving switches. Electromechanical switches, such as relay switches, are suitable for use with all types of loads, which may be resistive, capacitive, inductive. When connected in parallel with the relay switch, a semiconductor switch, such as a triac, may be provided that may utilize various loads to boost the load current to a current rating of the relay switch.

For the device, i.e. the load of the ac power source regulated/controlled by the electric switch, it is implemented to generate the phase advance line (phase line of voltage/current) and the neutral line (ground line) of the network. Nowadays, the power supply to the electric switch control unit, and possibly also to the electric switch itself, is provided directly on the mains power supply, i.e. arranged between the electric switch itself and the neutral line. It should be noted, however, that the neutral line of the grid is not always available. This is the case, for example, in internal wiring devices, in wall outlets (i.e., switches), in which no neutral wire is provided. In this case, the neutral wire must be installed afterwards if the power supply is to be supplied to the electric switch and its control unit in a conventional manner.

One of the problems with electric switches which can only use a live phase line as a power supply is that the control unit of the electric switch (and usually also the electric switch itself) requires a power supply both when the electric switch is conductive and when the electric switch is non-conductive in order to be able to operate properly. Since only the phase is shifted forward through the electric switch, there is no reference potential, such as ground potential, so that a voltage difference is generated, and the electric switch is accordingly arranged on the electric switch and its control unit.

In the prior art disclosed by US patent publication US-4,713,598, a relay switch is implemented without a neutral line by using only a live phase line, wherein the power supply to the amplifier of the PIR sensor is connected to the controller of the relay switch. Nowadays, relay switches are used as so-called two-wire switches. The relay switch is connected in parallel with the load and in parallel with the primary winding of the converter to the ac power grid. When the relay switch is switched on, the ac voltage of the primary winding of the current transformer is rectified, the result being the dc voltage required by the amplifier power supply. When the relay switch is opened and current cannot pass through the switch, the effective voltage across the switch is rectified and the desired operating voltage for the amplifier is generated.

When the relay switch is switched on and the load current flows through the switch, the voltage drop over the primary winding of the current transformer is very small compared to the load voltage prevailing over the load. Typically, this voltage drop is about 1% of the load voltage. The voltage drop prevailing in the primary winding is converted in the converter into a large secondary voltage on the secondary winding, which is rectified completely or partially by a diode, for which a bypass capacitor is provided as a filter for the pilot voltage and the rectified voltage for the amplifier is obtained at the diode. For example, when the load is 60 watts, the number of turns W1, W2 of the primary and secondary windings of the current transformer may be W1=45 and W2=2000. In addition, the primary winding also includes several impedance taps, in which case the turns ratio can be adjusted to accommodate the load.

The problem is that in such a construction and in these measures, the current transformer takes up a lot of space, especially in terms of turns. It is somewhat cumbersome to fit such converters in confined spaces of equipment, such as in mounting boxes for electric switches or similar electrical equipment.

Another problem is that the size of the load to be coupled in series with the converter is limited. Typically, the converters are designed for small loads, for example only for a 60 watt load, as in the example given in the above-mentioned us patent publication. If a similar converter is used with a larger load, the physical size of the converter is drastically increased.

Disclosure of Invention

The object of the present invention is to eliminate the drawbacks associated with the above-mentioned electric switching power supply. Another object of the invention is to achieve a new electric switching power supply which is particularly suitable for providing a power supply for a switch mounted in a mounting box of an electrical equipment system, in particular in a mortise and tenon mounted mounting box.

According to one aspect of the invention, a method for realising the supply of an electric switch (1) with electric power, wherein said switch is arranged in the current path (J) between an alternating current source (E) and a load (L) in order to interrupt and allow the supply to be switched on, and wherein the electric switch is also arranged in series with the primary winding (W1) of a current transformer (3) so that the electric power required by the control unit (2) of the switch and by itself is taken out on the switch when the switch is in the off position (a) and from the secondary winding (W2) of the current transformer through a rectifier (4) when the switch is on and can supply the load (L), is characterised in that: the converter (3) is arranged to be operable such that it is saturated every half cycle of the current from the alternating current source and rectifies the saturation peak (KP) of the secondary voltage of the secondary circuit (W2, W2a, W2 b) of said converter in order to obtain the direct current source when the switch (1) is on (k).

According to another aspect of the invention, a power supply arrangement for an electric switch (1), which is arranged in a current path (J) between an alternating current source (E) and a load (L) and which is set in an off (a) position and an on (k) position by means of a control unit in order to interrupt and allow the switching on of the power supply, and which comprises a converter (3), a rectifier (4) and a constant voltage source (5), wherein a primary winding (W1) of the converter (3) is arranged in series with the switch (1) in such a way that, when the switch is off (a) and the supply of the load is interrupted, the electric power required by the control unit (2) of the switch and by the switch itself is taken from the constant voltage source (5) at the switch, and, when the switch is on (k) and the supply of the load (L) is possible, the above-mentioned electric power is taken from a secondary winding (W2) of the converter by means of the rectifier (4), is characterized in that: the converter (3) is arranged to be operable such that it is saturated every half cycle of the current from the alternating current source and rectifies the saturation peak (KP) of the secondary voltage of the secondary circuit (W2, W2a, W2 b) of said converter in order to obtain the direct current source when the switch (1) is on (k).

The advantage of the invention is that a converter operating in the saturation range can be realized in a small size. The number of turns of the current transformer wire can be kept small, in which case the size of the current transformer can be made significantly smaller than in conventional current transformer constructions. This is particularly important when the electric switches, the converter and the auxiliary control unit have to be accommodated in a small space, in particular in an electric installation box.

Another advantage of the invention is that the converter can be used in a wide range of load powers, for example 25 w-3.7 kw. In this case, the load current may be in the range of 100 mA-16A.

Drawings

The invention is described in more detail below with reference to the attached drawing figures, wherein:

figure 1 illustrates the principle of the electrical switch of the invention applied to an electrical power supply;

figure 2 depicts the principle of another electrical switch according to the invention and the principle of the power supply according to the invention;

figure 3 is a schematic view of the invention with the power source actually applied to the electrical switch;

fig. 4A and 4B show secondary voltage curve forms for a current transformer with two loads.

Like reference numerals are used for like parts in the various figures.

Detailed Description

The invention relates to a power supply arrangement for an electrically controlled electric switch 1, such as an electromechanical switch and/or a semiconductor switch, wherein only one line is provided, i.e. the live phase line passes through the switch.

The electric switch 1 is arranged in a current path, for example in an electric line J between an alternating current source E (preferably one phase line in an alternating current network) and a load L, as shown in fig. 1 and 2. As far as the switch 1 is concerned, the power supply from the alternating current source E to the load L is switched off or interrupted and allowed to be switched on depending on the position of the switch, i.e. the switch is off in position a and the switch is on in the corresponding position k. By means of the control unit 2, the electric switch 1 is set in the off and on position. The function commands to the control unit 2 are preferably given from said control unit (see arrows in fig. 1 and 2) outside.

The power supply structure of the electric switch 1 comprises a converter 3, a rectifier 4 and a constant voltage source 5. The primary circuit W1 of the current transformer 3 is arranged in series with the electric switch 1. The power supply required by the electric switch 1 and its control unit 2 is arranged so that it is available at the electric switch 1 from the constant voltage source 5 when the switch is off a and the power supply is switched off, and from the secondary circuit W2 of the current transformer 3 via the rectifier 4 when the switch is on k and the alternating current from the alternating current source E is applied to the load L.

According to the invention the converter 3 is arranged to be operable such that the converter 3 is in a state of saturation for each half cycle of the grid current.

In a conventional ideal current transformer, the ratio of the currents in the primary and secondary circuits is inversely proportional to the winding turns ratio of the primary and secondary circuits. In practice, the magnitude of the magnetizing current produces a difference in current ratio. In order to keep this ratio of primary and secondary circuits in the controller as accurate as possible, the distortion caused by the magnetizing current must be minimized, i.e. the total amount of magnetizing current must be kept as small as possible. The greater the magnetic induction, the smaller the magnetizing current. The amount of magnetic induction is affected by the number of winding turns, the size of the transformer and the core material used.

Generally, the magnetizing current of the conventional current transformer is designed to be less than 3% of the current value to be measured.

The value of the secondary voltage U of a conventional converter is designed such that the value remains below the threshold voltage U _k This value of the secondary voltage U of 1 volt, since a high secondary voltage increases the value of the magnetizing current i:

wherein

L = inductance of the converter.

For this reason, the secondary winding of the current transformer is connected to a low-impedance load resistor, by means of which the value of the secondary voltage U is limited to a desired voltage value.

In the power supply of the invention, the current transformer 3 is arranged to be saturated, as described above. In this case, the secondary voltage U is not limited, as in a conventional current transformer, and the number of winding layers is arranged to be low. Both of these conditions raise the value of the magnetizing current so high that the current transformer is saturated.

The core material chosen for the current transformer 3 is a material with a high permeability P. Among these materials are pure iron (P = 180000), certain alloys of iron and nickel, such as 78 permalloy (P = 100000). One of the materials suitable for use as magnetic core materials and available on the market is NANOPERM ^TM . The saturation flux density of this material is 1.2T and the maximum permeability is 80000. The number of turns of the primary winding W1 of the current transformer 3 is arranged to be less than or equal to 10. Further, the cross-sectional area of the primary winding wire is arranged to be at least 0.75mm ² In order to enable the converter to handle high currents, such as 10A. Then, the number of turns of the secondary winding W2 of the current transformer 3 is arranged to be greater than or equal to 200. It is also advantageous to realize the magnetic core of the current transformer 3 by a toroidal ring.

As an illustrative example, the maximum value of the sinusoidal secondary voltage U of the secondary winding W2 is calculated below, which does not saturate the current transformer 3.

The maximum flux linkage of the current transformer is:

λ _max ＝N×A _c ×B _s

wherein

N = number of turns of winding 300

A _c = 0.24 × 10 cross-sectional area of the spiral tube ring ^-6 m ²

B _s = saturation flux density of spiral tube loop 1.2T

λ _max ≈8.64×10 ^-3 Vs

On the other hand, this flux linkage can also be calculated from the integral of the sinusoidal secondary voltage:

U _max = peak value of secondary voltage

ω = angular frequency 2 π f

Now, the value obtained for the flux linkage should be λ _max I.e. by

As is evident from fig. 4A and 4B, which will be discussed below, the peak value of the secondary voltage is at least 9V for the minimum load of the converter 3, which is significantly higher than the above-mentioned resulting maximum calculated value of 1.36V for a sinusoidal secondary voltage. Therefore, for this given initial value, the current transformer 3 is saturated.

In figure 2 another power supply configuration for the electric switch 1 according to the invention is shown. In this case, the electric switch 1 comprises, as a suitable switching element, a relay switch 11 which is a bistable relay switch. A bistable relay switch requires power only when its mode changes from on to off, or vice versa. Thus, it is an economical switching element from the viewpoint of power consumption. In this embodiment, the secondary winding W2 of the current transformer 3 comprises two windings W2a, W2b connected in series. The rectifiers are preferably full-wave rectifiers, the number of rectifiers being two: 4a, 4b. The input of the first rectifier 4a is connected only to the first winding W2a, while the input of the second rectifier 4b is connected to both second windings W2a, W2b. The constant voltage source 5 comprises two capacitors C1, C2, a first capacitor C1 being connected to the output of the first rectifier 4a and a second capacitor C2 being connected to the output of the second rectifier 4b.

An alternating current source E, for example a single-phase alternating current source, is applied to the load via a relay switch 11 of the electric switch and via the load to the zero point of the alternating current source, so that an electric circuit can be formed which can be switched on and correspondingly off by means of the relay switch. When the relay switch 11 of the electric switch is open, i.e. it is non-conductive, it represents a high impedance. Now, with a small current through the load L, the necessary electrical power required functionally by the electrical switching element can be generated. For this purpose, the ac voltage source 5 comprises a voltage step-down circuit 51, the voltage step-down circuit 51 being connected to the relay switch 11 and to the primary winding W1 of the current transformer 3. In the step-down circuit 51, the main power supply voltage E is converted into an appropriate low functional voltage. The capacitors C1 and C2 are now charged by said functional voltage. The control unit 2 of the electric switch is supplied with power from the first capacitor C1. In the capacitor C2, only the energy required to change the mode of the relay switch 11 is charged. When the relay switch 11 is in the stationary mode, the capacitor C2 is charged only by its own very low leakage current.

A control command is sent from the control unit 2 of the electric switch to switch the relay switch 11 on, i.e. into the conducting mode, by means of a suitable control pulse. The control unit 2 is, for example, controlled again by an external sensor (e.g. PIR) or by a timer. In the conducting mode, the relay switch 11 has a low impedance. When the relay switch 11 is switched on, the load current starts to advance through the relay switch 11, the main voltage over the electrical switch drops to near zero. The voltage of the capacitor C2 drops to a lower level than before because the relay switch 11 consumes the control power. The voltage of the capacitor C1 starts to drop because the control unit 2 is charging it all the time. The converter 3 starts to operate at the same time as the load current starts to pass through the relay switch. Since the secondary windings W2a and W2b of the current transformer 3 are connected in series, the voltage of the capacitor C2 is set to substantially the same level as the sum of the voltages obtained from the secondary windings (minus the voltage loss of the full-wave rectifier 4 b), and accordingly, the voltage of the capacitor C1 is set to the level of the voltage obtained from the first secondary winding W2 (minus the voltage loss of the full-wave rectifier 4 a). During this time, voltage balancing is achieved. Here, the leakage current of the capacitor C2 is equal to the charging current obtained from the converter 3. The voltage of the capacitor C2 is now sufficiently high to be able to open the relay switch 11 of the electric switch. The voltage of the capacitor C1 is at a level sufficient to maintain the electrical switch in operation.

A control command is sent from the control unit 2 again in order to switch off the relay switch 11 by means of a suitable control pulse. When the relay switch 11 is turned on, the control unit 2 is externally controlled in a similar manner to that described above. The path of the load current is now cut off. The mains voltage becomes active again on the electrical switch. The voltage level of the capacitor C2 may slightly decrease, but the capacitor immediately starts to be charged by the voltage-decreasing circuit 51. By charging in a similar manner, the voltage level of the capacitor C1 is maintained.

Figure 3 shows a third power supply configuration of the electric switch 1 of the invention. In this case, the electric switch comprises, as suitable switching element, a relay switch 11, in particular a bistable relay switch, and a bidirectional semiconductor switch 12, in this embodiment a bidirectional thyristor, connected in parallel therewith. As for the rest, the electric switch of figure 3 and its power supply correspond to the electric switch of figure 2 and its power supply. The semiconductor switch 12 is arranged to be on when the contacts of the relay switch 11 are opened and closed. In this way, the contact of the relay switch 11 can be prevented from spike formation. By means of the semiconductor switch 12, a so-called zero switch can also be realized. This means that the power supply of the load is always switched on and off at zero of the mains voltage. The advantage of this configuration is that it is possible to switch and control various types of loads-resistive, capacitive and inductive-by means of an electric switch.

In principle, the electric switch shown in figure 3 and its power supply operate in the same manner as described above in the embodiment of figure 2, where we refer to the functional description given above. The electrical switch of figure 3 is shown as an example of several preferred embodiments of the connection circuit of the capacitors C1, C2 and the voltage step-down circuit 51. The control unit 2 is also represented as two circuit units: a suitable control unit 2a and a power supply unit 2b for the switching means 11, 12. In this embodiment, the control unit is further controlled by a control signal obtained from the passive infrared sensor PIR.

The voltage-reducing circuit 51 includes a third capacitor C3, a resistor R1, and a zener diode Z1. The connection circuit of the first and second capacitors C1, C2 includes first and second diodes D1, D2, respectively. The capacitors C1, C2 are connected to the output of the

respective rectifier

4a, 4b. The diodes D1, D2 are connected in opposite directions, and the cathode terminals are connected to the voltage terminals of the capacitors C1, C2. The anode terminals of the diodes D1, D2 are connected to each other and also to the cathode terminal of a zener diode Z1, the zener diode Z1 being connected between the load L and the switch 11 via a resistor provided and a third capacitor C3. The anode terminal of the zener diode Z1 is connected to the alternating voltage source, i.e., to the phase advance terminal. The voltage terminal of the first capacitor C1 is connected to the control unit 2, in particular to the correct control unit 2a, so that its power supply can be provided. The voltage terminal of the second capacitor C2 is also connected to the control unit 2, in particular to the power supply unit 2b.

When the relay switch 11 of the electric switch is opened, the power supply of the control unit 2 is generated by means of the load L and the capacitor C3, the resistor R1 and the zener diode Z1 of the step-down circuit 51. Now, the capacitors C1, C2 are charged to the voltage potential limited by the zener diode Z1 (minus the threshold voltage of the diodes D1, D2).

When a control command is given from the control unit of the electric switch 1 to turn on the relay switch 11, the control unit 2 first sends a control pulse (with a duration of about 40 msec) to the semiconductor switch 12 and later (after about 10 msec) to the relay switch 11. Now the load current starts to pass through the

switches

11, 12.

When a control command is given from the control unit of the electric switch 1 to turn off the relay switch 11, the control unit 2 sends a control pulse (duration about 40 msec) to the semiconductor switch 12, and turns off the relay switch 11 later (after about 10 msec). The path of the load current is not interrupted and the main potential is again active at the electrical switch 1. The charging of the capacitor C2 is started through the capacitor 3 and the resistor R1 of the voltage-decreasing circuit 51 until the zener diode Z1 limits the rise of the voltage. The voltage of the capacitor C1 rises to the same potential.

The number of turns in the primary winding of the current transformer 3 is about 10 or even smaller. The number of wire turns in the first and second secondary windings W2a, W2b is about 200, preferably in the range of 200-400.

Fig. 4A shows the secondary voltage pulse of the current transformer 3 of the electric switch of fig. 3, which is measured by an oscilloscope, with a load L of 25 w incandescent lamp. The first secondary voltage U1 is measured across the first secondary winding W2 a. The second secondary voltage U2 is measured across the two secondary windings W2a and W2b. According to the measurement, the maximum voltage values of the saturation peaks of the secondary voltages U1, U2 are 9V and 14V, respectively. Fig. 4B shows the corresponding secondary voltages U1, U2 when an incandescent lamp with a 100 watt load is used. For larger load currents, the duration of the saturation peak KP of the secondary voltages U1, U2 is shortened, but the corresponding voltage levels are raised. Now, according to the measurement results, the maximum voltage values of the saturation peaks KP of the secondary voltages U1, U2 are 18V, 30V, respectively.

According to a preferred embodiment of the invention, the electric switch 1 and its power supply structure are mounted in a wall box, in particular a mortise mounted wall box with limited space for the electric switch elements. The current transformer 3 of the electric switch 1 is arranged on a spiral pipe ring with an outer diameter of 20 mm. The material used for the coil loops was NANOPERMTM material (manufacturer: MAGNETEC GmbH). Now, a table is given of the number of winding turns of the current transformer 3 and the wires used:

w1:6 turns of 0.75mm ² Insulated wire

W2a: 300 turns of copper with phi 0.18mm

W2b: 200 turns of copper with phi 0.18mm

From the tests carried out, it was found that the electric switch can be operated without failure at the desired load current of 100 mA-10A.

The invention is not limited to the preferred embodiments described above, but many modifications are possible within the scope of the inventive concept defined by the claims.

Claims

1. A method for realising the supply of electric power to an electric switch (1), wherein said switch is arranged in the current path (J) between an alternating current source (E) and a load (L) in order to interrupt and allow the supply to be switched on, and the electric switch is also arranged in series with the primary winding (W1) of a current transformer (3) so that the electric power required by the control unit (2) of the switch and by the switch itself is taken out on the switch when the switch is in the off position (a) and taken out from the secondary winding (W2) of the current transformer through a rectifier (4) when the switch is on and can supply power to the load (L), characterised in that: the converter (3) is arranged to be operable such that it is saturated every half cycle of the current from the alternating current source and rectifies the saturation peak (KP) of the secondary voltage of the secondary circuit (W2, W2a, W2 b) of said converter in order to obtain the direct current source when the switch (1) is on (k).

2. A power supply arrangement for an electric switch (1), which switch is arranged in a current path (J) between an alternating current source (E) and a load (L) and which switch is set in an off (a) position and an on (k) position by means of a control unit in order to interrupt and allow the power supply to be switched on, and which power supply arrangement comprises an inverter (3), a rectifier (4) and a constant voltage source (5), wherein a primary winding (W1) of the inverter (3) is arranged in series with the switch (1) in such a way that, when the switch is off (a) and the supply to the load is interrupted, the electric power required by the control unit (2) of the switch and by the switch itself is taken from the constant voltage source (5) over the switch and, when the switch is on (k) and the supply to the load (L) is possible, the aforementioned electric power is taken from a secondary winding (W2) of the inverter by means of the rectifier (4), characterized in that: the converter (3) is arranged to be operable such that it is saturated every half cycle of current from the alternating current source and rectifies the saturation peak (KP) of the secondary voltage of the secondary circuit (W2, W2a, W2 b) of said converter in order to obtain the direct current source when the switch (1) is on (k).

3. The power supply structure for an electric switch according to claim 2, characterized in that the magnetic core material of the current transformer (3) is a material with high magnetic permeability.

4. Power supply configuration for an electric switch according to claim 3, characterized in that the number of turns of the primary winding (W1) of the current transformer (3) is equal to or less than 10.

5. Power supply arrangement for an electric switch, according to claim 4, characterized in that the cross-sectional area of the wire of the primary winding (W1) of the current transformer is at least 0.75mm ² 。

6. The power supply configuration for electric switches according to claim 3, 4 or 5, characterized in that the magnetic core of the current transformer (3) is realized by means of a toroidal ring.

7. The power supply structure for an electric switch according to claim 3, 4 or 5, characterized in that the number of turns of the secondary winding (W2, W2a, W2 b) of the current transformer (3) is greater than or equal to 200.

8. The power supply arrangement for an electric switch according to claim 3, 4 or 5, characterized in that the electric switch comprises a relay switch (11) and the current transformer (3) comprises a secondary winding (W2) with two windings (W2 a, W2 b) connected in series, whereby power is supplied to the control unit (2) and to the relay switch (11).