WO1998059353A1

WO1998059353A1 - A control device and a method for controlling an electromagnetic actuator for electric circuit breakers

Info

Publication number: WO1998059353A1
Application number: PCT/SE1998/001131
Authority: WO
Inventors: Assadollah Abri; Leif Lundin; Magnus FORSÉN
Original assignee: Abb Ab
Priority date: 1997-06-12
Filing date: 1998-06-12
Publication date: 1998-12-30
Also published as: AU7947498A; SE9702247D0

Abstract

The present invention relates to a control device and a method for controlling an electromagnetic actuator for electric circuit breakers, said actuator comprising a trip magnet (12) and a closing magnet (14) for actuating the movable contact system of the circuit breaker. The control device (10) comprises a power source (16) connected to the trip magnet (12) and to the closing magnet (14). The control device (10) also comprises a first switching means (18) connected between the power source (16) and the trip magnet (12), and a second switching means (20) connected between the power source (16) and the closing magnet (14) for connecting or disconnecting the power supply to the trip or closing magnet (12, 14), respectively. The control device (10) comprises at least one detector (22, 24) to detect the contact positions of the trip magnet (12) and the closing magnet (14). The detector (22, 24) is connected to a control unit (26) which controls closing or tripping of the switching means (18, 20).

Description

A CONTROL DEVICE AND A METHOD FOR CONTROLLING AN ELECTROMAGNETIC ACTUATOR FOR ELECTRIC CIRCUIT BREAKERS

Technical field

The present invention relates to a control device for controlling an electromagnetic actuator for a medium-voltage or high-voltage electric circuit breaker, said actuator comprising a trip magnet and a closing magnet for actuating the movable contact system of the circuit breaker. The present invention also relates to a method of controlling an electromagnetic actuator intended for a medium-voltage or high-voltage circuit breaker, by means of a control device.

Background art Spring actuators and hydraulic and pneumatic actuators are used to a great extent for actuating medium-voltage and high-voltage circuit breakers. Actuators of these types often include a large number of different components, which results in relatively high manufacturing costs.

Electromagnetic actuators have hitherto been used primarily for low- voltage circuit breakers. In smaller circuit breakers of this type it is usual for the tensile force of the electromagnet to be combined with the force of a return spring so that the movable contact system can be displaced in opposite directions (closing and breaking).

Electromagnetic actuators have also been used in older high-voltage circuit breakers of the type in which the contact system is enclosed in an earthed, oil-filled tank. In a known actuator of this type two separate magnets are used for tripping and closing, respectively. The magnets are connected to the contact system via a mechanism constructed of a plurality of arms, links and rods. However, due to its relatively considerable weight, friction in all the pivot bearings, etc., such mechanisms operate sluggishly and are energy-consuming. International patent application WO 96/09636 shows an electro-magnetic actuator designed for a medium-voltage or high-voltage circuit breaker. The actuator comprises a trip magnet and a closing magnet, each comprising an operating coil, a magnetic core and an armature to influence the movable contact system of the circuit breaker.

The two magnetic cores and connecting magnetic yoke are integrated to a single magnet body. The operating coils are connected to a common power source via separate thyristor couplings. Through activation of one or other operating coil, the two armatures are translatoriaily displaceable along the longitudinal axis of the magnet body to either trip or close the circuit breaker.

Description of the invention The object of the present invention is to provide a control device of the type described in the preamble to claim 1 and a control method of the type described in the preamble to claim 12, wherein the control device and control method bring about real-time control of the forces required for tripping or closing a circuit breaker. The result is greater reliability, better economy of energy and the opportunity of optimizing the dimensions of the magnet pistons in the actuator better than in comparable previously known constructions. This is achieved according to the invention by a control device having the features defined in the characterizing part of claim 1 and by a method having the features defined in the characterizing part of claim 12.

The basis of the present invention is . a control device for an electromagnetic actuator for circuit breakers, said actuator comprising an armature for obtaining the actuating movement, which armature is arranged to perform a first actuating movement influenced by a first magnetic device and which armature is arranged to perform a second actuating movement influenced by a second magnetic device. In order to achieve a first actuating movement the control device supplies energy for excitation of the first magnetic device and to achieve a second actuating movement the control device supplies energy for excitation of the second magnetic device. To achieve the first actuating movement during a first period of the movement the control device supplies energy to the first magnetic device and to retard the movement during a second period of the movement the control device supplies energy to the second magnetic device.

The first period of the movement and the second period of the movement are preferably separated by an intermediate period during which no energy is supplied to either of the magnetic devices.

The first magnetic device preferably consists of a trip magnet and the sec- ond magnetic device of a closing magnet, both the trip magnet and the closing magnet being connected to a common power source. Connected between the power source and the trip magnet and between the power source and the closing magnet, respectively, are switching means, both switching means being connected to a control unit. The control device ac- cording to the invention also comprises at least one detector connected to the trip magnet and to the closing magnet, respectively, and the control unit. The control unit controls closing and opening of the two switching means, entailing excitation or de-energizing of the trip and closing magnets, respectively. When at least one detector detects that the circuit breaker is in off position it emits a detector signal to the control unit which causes the first switching means to be opened, thereby de-energizing the trip magnet. When the detector detects that the circuit breaker is in on position it emits a detector signal to the control unit causing the second switching means to be opened, thereby de-energizing the closing magnet.

The method of controlling an electromagnetic actuator for electric circuit breakers by means of a control device according to the invention comprises the following steps. An armature is arranged in the actuator to obtain the actuating movement, which armature is arranged to perform a first actuating movement influenced by a first magnetic device and which armature is arranged to perform a second actuating movement influenced by a second magnetic device. A first actuating movement is achieved by energy being supplied for excitation of the first magnetic device and a second actuating movement is achieved by energy being supplied for excita- tion of the second magnetic device. To achieve the first actuating movement during a first period of the movement the control device supplies en- ergy to the first magnetic device and to achieve retardation of movement during a second period of the movement the control device supplies energy to the second magnetic device. The first period of the movement and the second period of the movement are preferably separated by an inter- mediate period during which no energy is supplied to either magnetic device.

The invention will be explained in more detail in the following detailed description of a preferred embodiment, with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 shows a block diagram of a control device according to a first embodiment of the present invention; Figure 2a shows a current-time diagram of the tripping current, l_0ff;

Figure 2b is a diagram showing the position X of the circuit breaker in relation to the time when the tripping current, l_0ff, follows the course shown in Figure 2a; Figure 3b shows a current-time diagram of the closing current, l_on; Figure 3b is a diagram showing the position X of the circuit breaker in relation to the time when the closing current, l_on, follows the course shown in Figure 3a; Figure 4 is a flowchart showing a procedure according to the present invention for controlling an electromagnetic actuator for elec- trie circuit breakers by means of a control device according to a first embodiment of the present invention; Figure 5 shows schematically how an electromagnetic actuator that can be controlled by the control device according to the present invention may be constructed; Figure 6 shows a block diagram of a control device according to a second embodiment of the present invention; Figure 7a shows a current-time diagram for the tripping current, l_0ff, for the control device shown in Figure 6; and Figure 7b shows a current-time diagram for the average current through the trip magnet in the control device shown in Figure Detailed description of embodiments of the present invention

Figure 1 shows a block diagram of a control device 10 according to the present invention. The control device (10) is intended to control an elec- tromagnetic actuator for electric circuit breakers, the actuator being illustrated in Figure 1 by a trip magnetic 12 and a closing magnet 14. The control device 10 comprises a common power source 16 which is connected to the trip magnet 12 and the closing magnet 14. The power source 16 may consist, for instance, of a capacitor, accumulator or dry-cell battery with means for automatic charging. The control device 10 also comprises a first switching means 18 connected between the power source 16 and the trip magnet 12, and a second switching means 20 connected between the power source 16 and the closing magnet 14, in order to connect or disconnect the supply of energy from the trip or closing magnet 12, 14, respectively. The control device 10 also comprises at least one detector to detect the contact positions of the trip magnet 12 and the closing magnet 14. The detector is also connected to a control unit 26 which is also connected to the first and the second switching means 18, 20, respectively. The control unit 26 controls connection and disconnec- tion of the switching means 18, 20. In the embodiment shown in Figure 1 the control device 10 comprises two detectors, a first detector 22 connected to the trip magnet 12 and the control unit 26, and a second detector 24 connected to the closing magnet 14 and the control unit 26. The switching means 18, 20 shown may consist of MOSFET transistors or thy- ristors, e.g. GTO or IGBT thyristors.

The following is a description of the function of the control device 10 shown in Figure 1. When the circuit breaker is tripped the control unit 26 emits a control signal to the first switching member 18, which is thereby closed. This causes energy in the form of the tripping current, l₀ff, to be supplied from the power source 16 to the trip magnet 12 so that it is energized. The movable contact system (not shown) of the circuit breaker is thus moved to the off position. If the switching means 18, 20 consists of thyristors then said control signal from the control unit 26 will consist of a control current to ignite the thyristors. When the common detector or the first detector 22 according to Figure 1 detects that the circuit breaker is in off position, it emits a detector signal to the control unit 26, whereupon the control unit 26 emits a control signal to the first switching means 18 to open it. Upon opening of the switching means 18 the supply of energy to the trip magnet 12 is cut and it is thus de-energized.

When the circuit breaker is closed the control unit 26 emits a control signal to the second switching means 20, which is thereby closed. This causes energy in the form of the closing current, l₀n- to be supplied from the power source 16 to the closing magnet 14 so that it is energized. The movable contact system (not shown) of the circuit breaker is thus moved to the on position. In this case also the control signal from consists of a control current if the switching means 20 consists of a thyristor, for instance. When the common detector or the second detector 24 according to Figure 1 detects that the circuit breaker is in on position, it emits a de- tector signal to the control unit 26, whereupon the control unit 26 emits a control signal to the second switching means 20 to open it. Upon opening of the switching means 20 the supply of energy, in the form of the closing current l₀n, to the closing magnet 14 is cut and it is thus de-energized.

Figure 2a shows a current-time diagram for the tripping current, l₀ff. and Figure 2b shows a diagram indicating the position, X, of the circuit breaker in relation to the time when the tripping current, l₀ff, follows the course shown in Figure 2a. As is clear from Figure 2b, the circuit breaker is in closed position at the time t = 0 and in open position at the time \2- The time ti in Figure 2a indicates the time when the first switching means 18 closes after having received a control signal from the control unit 26, whereupon the tripping current l₀ff is supplied to the trip magnet 12. The time t2 in Figure 2a indicates the time when the first switching means 18 opens after having received a control signal from the control unit 26, whereupon supply of the tripping current l₀ff is cut. The broken line in Figure 2a indicates what the tripping current l₀ff might have looked like if the control device 10 according to the present invention had not been used. The supply of the tripping current, l₀ff, is not cut until the time t2', i.e. the tripping current is supplied for a longer period t2'-tι , than is the case with the use of the present invention where the period would be t2-t-| . The control device 10 according to the present invention limits the duration of the driving current (tripping or closing current) to the force and energy required for each operation (tripping or closing of the circuit breaker). The invention thus saves energy. If for some reason the movement of the cir- cuit breaker becomes slower, the duration of the driving current is automatically adjusted to the new situation which, in this case, requires more energy.

Figure 3a shows a current-time diagram for the closing current, l₀n, and Figure 3b shows a diagram indicating the position, X, of the circuit breaker in relation to the time when the closing current, l_on, follows the course shown in Figure 3a. As is clear from Figure 3b, the circuit breaker is in open position at the time tβ and in closed position at the time ty The time t3 in Figures 3a and 3b indicates the time when the second switching means 20 closes after having received a control signal from the control unit 26, whereupon the closing current, l₀n, is supplied to the closing magnet 14. The time in Figures 3a and 3b indicates the time when the second switching means 20 opens after having received a control signal from the control unit 26, whereupon supply of the closing current, l_on, is cut. The broken line in Figure 3a indicates what the closing current, l_on, might have looked like if the control device 10 according to the present invention had not been used. The supply of the closing current, l_on, is not cut until the time ty, i.e. the closing current is supplied for a longer period t4^*-t3, than is the case with the use of the present invention where the period would be t4-t3. The invention thus saves energy in this case also.

Figure 4 shows a flowchart for a process according to the present invention of controlling an electromagnetic actuator for circuit breakers, by means of a control device. The process starts at block 40. At block 42 the question is asked as to whether the circuit breaker shall be switched off. If the answer is negative the process continues to block 44 where the question is asked as to whether the circuit breaker is to be switched on. If the answer is negative the process returns to block 40. If an affirmative response is obtained at block 42, however, the process continues to block 46, whereupon the control unit 26 (see Figure 1 ) emits a control signal to close the first switching means 18. If the switching means consists of a thyristor the control signal will consist of a control current for igniting the thyristor. When the first switching means 18 closes energy, in the form of the tripping current l₀ff, is supplied from the power source 16 to the trip- ping magnet 12. This results in excitation of the trip magnet 12 at block 48. The process then continues to block 50 where the question is asked as to whether the circuit breaker is in off position. If the answer is negative block 50 will be repeated until an affirmative answer is obtained, after which the process continues to block 52. If the common detector or, as in Figure 1 , the first detector 22 detects that the circuit breaker is in off position, i.e. an affirmative answer is obtained at block 50, the detector will send a detector signal to the control unit 26 at block 52. Thereafter, at block 54, the control unit 26 sends a control signal to the first switching means 18 to open this. This cuts the supply from the tripping current l₀ff, with the result that the trip magnet 12 is de-energized at block 56. The circuit breaker is in off position at this stage. From here the process returns to start position, i.e. to block 40. If, on the other hand, an affirmative response is obtained at block 44, i.e. if the circuit breaker is to be switched on, the process continues to block 58, whereupon the control unit 26 emits a control signal to the second switching mean 20 to close it. If the switching means 20 consists of a thyristor, the control signal consists of a control current for ignition of the thyristor. When the second switching means 20 closes energy, in the form of the closing current l_on, is supplied from the power source 16 to the closing magnet 14 at block 60. The process then continues to block 62 where the question is asked as to whether the circuit breaker is in on position. If the answer is negative block 62 will be repeated until an affirmative answer is obtained, after which the process continues to block 64. If the common detector or, as in Figure 1 , the second detector 24 detects that the circuit breaker is in on position, i.e. an af- firmative answer is obtained at block 62, the detector will send a detector signal to the control unit 26 at block 64. Thereafter, at block 66, the control unit 26 sends a control signal to the second switching means 20 to open this. This cuts the supply from the closing current l_on, with the result that the closing magnet 14 is de-energized at block 68. The circuit breaker is in on position at this stage. From here the process returns to start position, i.e. to block 40.

Figure 5 shows schematically an electromagnetic actuator that can be controlled by the control device according to the present invention. The actuator in Figure 5 comprises a magnetic device consisting of a trip magnet 70 comprising a tripping coil 72, a magnetic core 74 and a tripping armature 76, and also a closing magnet 78 comprising a closing coil 80, a magnetic core 82 and a closing armature 84. The two magnetic cores 74, 82, with connecting magnetic yoke, are integrated to form a single magnetic body 86 which, together with the coils 72, 80 and the armature 76, 84, forms an actuating magnet with rotationally symmetrical configuration.

The magnetic body 86 has two cylindrical spaces 88, 90, separated by a transverse yoke 92 arranged in the mid-section of the magnetic body. The tripping coil 72 is arranged in the upper space 88, whereas the closing coil 80 is arranged in the lower space 90. The tripping armature 76 which protrudes into the space 88 at the upper end of the magnetic body 86, is connected to the movable contact system of the circuit breaker via an insu- lating operating rod 94. The closing armature 84 which protrudes into the space 90 at the lower end of the magnetic body 86, is provided with (or abuts against) a metallic push rod 96 (non-magnetic) which extends axially through the magnetic body 86.

Figure 6 shows a block diagram of a control device according to a second embodiment of the present invention. Similar parts in Figures 1 and 6 have been given the same designations in order to simplify the description of Figure 6. The control device 10 is intended to control an electromagnetic actuator for electric circuit breakers. The actuator is illustrated in Figure 6 by a trip magnetic 12, a closing magnet 14, a tripping armature 100 and a closing armature 102. The control device 10 comprises a common power source 16 which is connected to the trip magnet 12 and the closing magnet 14. As in the embodiment according to Figure 1 the power source 16 may consist, for instance, of a capacitor, accumulator or dry-cell battery with means for automatic charging. The control device 10 also comprises a first switching means 18 connected between the power source 16 and the trip magnet 12, and a second switching means 20 connected between the power source 16 and the closing magnet 14, in order to connect or disconnect the supply of energy from the trip or closing magnet 12, 14, respectively. The control device 10 also comprises at least one detector to detect the contact positions of the trip magnet 12 and the closing magnet 14. The detector is also connected to a control unit 26 which is also connected to the first and the second switching means 18, 20, respectively. The control unit 26 controls connection and disconnec- tion of the switching means 18, 20. In the embodiment shown in Figure 6 the control device 10 comprises two detectors, a first detector 22 connected to the trip magnet 12 and the control unit 26, and a second detector 24 connected to the closing magnet 14 and the control unit 26. The switching means 18, 20 shown may consist of MOSFET transistors or thy- ristors, e.g. GTO or IGBT thyristors. The control device 10 also comprises at least one position transducer for sensing the position of the tripping armature 100 and closing armature 102, respectively. The position transducer is also connected to the control unit 26 which receives signals from the position transducer indicating the positions of the tripping armature 100 and closing armature 102, respectively. In the embodiment shown in Figure 6 the control device 10 comprises two position transducers, a first position transducer 104 connected to the tripping armature 100 and the control unit 26, and a second position transducer 106 connected to the closing armature 102 and the control unit 26.

The following is a description of the function of the control device 10 shown in Figure 6. When the circuit breaker is tripped the control unit 26 emits a control signal to the first switching member 18, which is thereby closed. This causes energy in the form of the tripping current, l₀ff, to be supplied from the power source 16 to the trip magnet 12 so that it is energized. This excitation of the trip magnet 12 causes the tripping armature 100 to be moved as a result of a force transferred to the circuit breaker, which force is proportional to the square of the current through the magnet, i.e. F ~ k . |2 The first position transducer 104 continuously transmits information concerning the position of the tripping armature 100 to the control unit 26. With the object of controlling the force required to influence the circuit breaker, the control unit 26 controls the average current through the trip or closing magnet 12, 14. This is performed by means of pulse width modulation, which means that the control unit 26 alternately closes and opens the first switching means 18 so that the trip magnet 12 is alternately connected to and not connected to the power source 16. When the common detector or the first detector 22 according to Figure 6 detects that the cir- cuit breaker is in off position, it emits a detector signal to the control unit 26, whereupon the control unit 26 emits a control signal to the first switching means 18 to open it. Upon opening of the switching means 18 the supply of energy to the trip magnet 12 is cut and it is thus de-energized.

When the circuit breaker is closed the control unit 26 emits a control signal to the second switching member 20, which is thereby closed. This causes energy in the form of the closing current, l₀n, to be supplied from the power source 16 to the closing magnet 14 so that it is energized. This excitation of the trip magnet 14 causes the closing armature 102 to be moved as a result of a force transferred to the circuit breaker, which force is proportional to the square of the current through the magnet. The second position transducer 106 continuously transmits information concerning the position of the closing armature 102 to the control unit 26. In similar manner to the description above for tripping of the circuit breaker, the control unit 26 controls the average current through the closing magnet 14 by means of pulse width modulation. The control unit 26 thus alternately opens and closes the second switching means 20 so that the closing magnet 14 is alternately connected to and not connected to the power source 16. When the common detector, or the second detector 24 accord- ing to Figure 6 detects that the circuit breaker is in on position, it emits a detector signal to the control unit 26, whereupon the control unit 26 emits a control signal to the second switching means 20 to open it. Upon opening of the switching means 20 the supply of energy, in the form of the closing current l_on, to the trip magnet 14 is cut and it is thus de-energized. This pulse width modulation technique enables the speed of the circuit breaker to be reduced at its end positions, thereby reducing wear on the circuit breaker and increasing its service life.

Figure 7a shows a current-time diagram for the tripping current, l₀ff, for the control device shown in Figure 6. The time ti in Figure 7a indicates the time when the first switching means 18 closes after having received a control signal from the control unit 26, whereupon the tripping current l₀ff is supplied to the trip magnet 12. The time t2 in Figure 7a indicates the time when the first switching means 18 opens after having received a control signal from the control unit 26, whereupon supply of the tripping current l₀ff is cut. Note that at this time, t2, the breaker is not in its off position. The tripping armature 100 has only just commenced its movement. At the time t3 the control unit 26 again transmits a control signal to the first switching means 18 to close it, whereupon the tripping current l₀ff is again supplied to the trip magnet 12. At the time t^ the first switching means 18 is opened, whereupon the supply of the tripping current l₀ff is cut. This pulse width modulation continues until the first detector 22 detects that the circuit breaker is in off position, which occurs at the time t_n. The last time interval when the first switching means 18 is closed is between t_n-t_n-i - The pulse width modulation controlled from the control unit 26 is influenced by and occurs dependent upon the information obtained from the first position transducer 104 concerning the position of the tripping armature 100.

Figure 7b shows a current-time diagram for the average current, , through the trip magnet in the control device shown in Figure 6. This fig- ure shows the average current, , when the pulse width modulation is controlled in agreement with Figure 7a. At the time t-i, when the first switching means 18 closes and immediately thereafter, the average current, , through the trip magnet 12 increases rapidly. The average current continues to increase during the time interval t2-tι , although the increase per time unit becomes less. At the time t2, when the first switching means 18 opens, the average current, , through the trip magnet de- creases. In this case the average current, , levels out to a constant level. At the time t_n the average current, , diminishes rapidly since the first switching means 18 opens. This pulse width modulation thus enables the speed of the circuit breaker to be reduced at its end positions, thereby reducing wear on the breaker and increasing its service life.

The invention is not limited to the embodiments shown. Many modifications are possible within the scope of the appended claims.

Claims

C L A I M S

1. A control device (10) for an electromagnetic actuator for electric circuit breakers, said actuator comprising an armature (100, 102) for ob- taining the actuating movement, which armature is arranged to perform a first actuating movement influenced by a first magnetic device (12) and which armature (100, 102) is arranged to perform a second actuating movement influenced by a second magnetic device (14), wherein in order to achieve a first actuating movement the control device (10) supplies en- ergy for excitation of the first magnetic device (12) and to achieve a second actuating movement the control device supplies energy for excitation of the second magnetic device (14), characterized in that in order to achieve the first actuating movement during a first period of the movement the control device (10) supplies energy to the first magnetic device (12) and in that to retard the movement during a second period of the movement the control device (10) supplies energy to the second magnetic device (14).

2. A control device (10) as claimed in claim 1 , characterized in that the first period of the movement and the second period of the movement are separated by an intermediate period during which no energy is supplied to either of the magnetic devices (12, 14).

3. A control device (10) as claimed in claim 2, characterized in that the first magnetic device (12) consists of a trip magnet (12), in that the second magnetic device (14) consists of a closing magnet (14), and in that the control device (10) comprises a power source (16) connected to the trip magnetic (12) and to the closing magnet (14), a first switching means (18) connected between the power source (16) and the trip magnet (12), a second switching means (20) connected between the power source (16) and the closing magnet (14), at least one detector (22, 24) connected to the trip magnet (12) and to the closing magnet (14) to detect the contact positions of the trip magnet (12) and the closing magnet (14), and a control unit (26) connected to the detector (22, 24) and to the first switching means (18) and the second switching means (20) to control the energy supplied to the trip magnet (12) or to the closing magnet (14) depending on the detector signals from the detector (22, 24) for tripping or closing the circuit breaker.

4. A control device (10) as claimed in claim 3, characterized in that the control device (10) comprises two detectors (22, 24), the first detector (22) being connected between the trip magnet (12) and the control unit (26) to detect the position of the piston of the trip magnet (12) and the second detector (24) being connected between the closing magnet (14) and the control unit (26) to detect the position of the piston of the closing magnet (14).

5. A control device (10) as claimed in claim 4, characterized in that the power source (16) consists of a capacitor, accumulator or dry-cell battery provided with means for automatic charging.

6. A control device (10) as claimed in any of claims 3-5, characterized in that the control device (10) also comprises a first position transducer (104) connected between the armature (100) of the trip magnet (12) and the control unit (26) and a second position transducer (106) connected between the armature (102) of the closing magnet (14) and the control device (26), said control unit (26), dependent on signals from the position transducers (104, 106), controlling the average current supply to the trip magnet (12) or to the closing magnet (14) by means of pulse width modulation.

7. A control device (10) as claimed in claim 6, characterized in that the first switching means (18) consists of a first GTO thyristor (18) and in that the second switching means (20) consists of a second GTO thyris- tor (20).

8. A control device (10) as claimed in claim 6, characterized in that the first switching means (18) consists of a first IGBT thyristor (18) and in that the second switching means (20) consists of a second IGBT thyristor (20).

9. A control device (10) as claimed in claim 6, characterized in that the first switching device (18) consists of a first MOSFET transistor (18) and in that the second switching means (20) consists of a second MOSFET transistor (20).

10. A control device (10) as claimed in claims 3-5, characterized in that the first switching means (18) consists of a first electronic control unit (18) to vary the current supply to the trip magnet (12) and in that the sec- ond switching means (20) consists of a second electronic control unit (20) to vary the current supply to the closing magnet (14), said current supplies being varied in relation to the position of the circuit breaker.

11. A control device (10) as claimed in claim 10, characterized in that the detectors (22, 24) consist of position transducers (22, 24).

12. A method of controlling an electromagnetic actuator for electric circuit breakers by means of a control device (10), said actuator comprising an armature (100, 102) for obtaining the actuating movement, which armature (100, 102) is arranged to perform a first actuating movement influenced by a first magnetic device (12) and which armature (100, 102) is arranged to perform a second actuating movement influenced by a second magnetic device (14), a first actuating movement being achieved by energy being supplied for excitation of the first magnetic device (12) and a second actuating movement being achieved by energy being supplied for excitation of the second magnetic device (14), characterized in that in order to achieve the first actuating movement during a first period of the movement energy is supplied by the control device (10) to the first magnetic device (12) and in that in order to achieve retardation of movement energy is supplied by the control device (10) during a second period of the movement, to the second magnetic device (14).

13. A method as claimed in claim 12, characterized in that the first period of the movement and the second period of the movement are sepa- rated by an intermediate period during which no energy is supplied to either of the magnetic devices (12, 14).

14. A method as claimed in claim 13, characterized in that the first magnetic device (12) consists of a trip magnet (12), and in that the second magnetic device (14) consists of a closing magnet (14), the control device (10) comprising a power source (16) connected to the trip magnetic (12) and to the closing magnet (14), a first switching means (18) connected between the power source (16) and the trip magnet (12), a second switching means (20) connected between the power source (16) and the closing magnet (14), at least one detector (22, 24) connected to the trip magnet (12) and to the closing magnet (14) and a control unit (26) connected to the detector (22, 24) and to the first switching means (18) and the second switching means (20), said method comprising the following steps for tripping the circuit breaker: that the control unit (26) emits a control signal to close the first switching means (18), whereupon energy is supplied from the power source (16) to the trip magnet (12) for excitation thereof; that, upon detecting the off position of the circuit breaker, the detector (22, 24) emits a first detector signal to the control unit (26), and; that the control unit (26), in response thereto, emits a control signal to the first switching means (18), opening said means for de- energizing the trip magnet (12); and said method being characterized be the following steps for closing the circuit breaker: that the control unit (26) emits a control signal to close the second switching means (20), whereupon, energy is supplied from the power source (16) to the closing magnet (14) 'for excitation thereof; that, upon detecting the on position of the circuit breaker, the detector (22, 24) emits a second detector signal to the control unit (26), and; that the control unit (26), in response thereto, emits a control signal to the second switching means (20), opening said means for de- energizing the closing magnet (14). 1 o

15. A method as claimed in claim 14, wherein the control device (10) comprises two detectors (22, 24), the first detector (22) being connected between the trip magnet (12) and the control unit (26) and the second detector (24) being connected between the closing magnet (14) and the control unit (26), which method is characterised in that the detecting steps also include the following steps: that, upon detecting of the position of the piston of the trip magnet (12) signifying off position of the circuit breaker, the first detector (22) emits a first detector signal to the control unit (26), and ΓÇó that, upon detecting of the position of the piston of the closing magnet (14) signifying on position of the circuit breaker, the second detector (24) emits a second detector signal to the control unit (26).

16. A method as claimed in claim 15, wherein the control device (10) also comprises a first position transducer (104) connected between the armature (100) of the trip magnet (12) and the control unit (26) and a second position transducer (106) connected between the armature (102) of the closing magnet (14) and the control device (26), which method is characterized by the following steps upon tripping of the circuit breaker: ΓÇó that the first position transducer (104) continuously transmits information concerning the position of the trip armature (100) to the control unit (26); that, depending on the information from the first position transducer (104), the control unit (26) alternately closes and opens the first switching means (18) for pulse width modulation of the average current supply to the trip magnet (12); and which method is characterized by the following steps upon closing of the circuit breaker: that the second position transducer (106) continuously transmits information concerning the position of the trip armature (102) to the control unit (26); that, depending on the information from the second position transducer (106), the control unit (26) alternately closes and opens the second switching means (20) for pulse width modulation of the average current supply to the closing magnet (14).

17. A method as claimed in claim 15 or claim 16, wherein the first switching means (18) consists of a first GTO thyristor (18) and the second switching means (20) consists of a second GTO thyristor (20), wherein the excitation step upon the circuit breaker being switched off is characterized by: the control unit (26) transmitting a control current signal to the first GTO thyristor (18) for ignition thereof, whereupon a current (l_0ff) is supplied from the power source (16) to a trip coil (72) in the trip magnet (12) for excitation of the trip magnet (12), and; wherein the excitation step upon the circuit breaker being switched on is characterized by: the control unit (26) transmitting a control current signal to the second GTO thyristor (20) for ignition thereof, whereupon a current (l_on) is supplied from the power source (16) to a closing coil (80) in the closing magnet (14) for excitation of the closing magnet (14).

18. A method as claimed in claim 15, wherein the first switching means (18) consists of a first electronic control unit (18) and the second switching means (20) consists of a second electronic control unit (20), and wherein the detector (22, 24) consists of a position transducer (22, 24), wherein the excitation step upon the circuit breaker being switched off is characterized by: the control unit (26) transmitting a control current signal to the first control unit (18), whereupon a current (l_0ff) is supplied from the power source (16) to a trip coil (72) in the trip magnet (12), and; wherein the excitation step upon the circuit breaker being switched on is characterized by: the control unit (26) transmitting a control current signal to the second control unit (20), whereupon a current (l_on) is supplied from the power source (16) to a closing coil (80) in the closing magnet (14) for excitation of the closing magnet (14).