EP2850632B1

EP2850632B1 - Regulated power supply assembly for use in electrical switch

Info

Publication number: EP2850632B1
Application number: EP12813316.2A
Authority: EP
Inventors: Vijay LIMAYE
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG
Priority date: 2012-12-18
Filing date: 2012-12-18
Publication date: 2017-11-01
Anticipated expiration: 2032-12-18
Also published as: WO2014094830A1; CN104620347A; EP2850632A1

Description

The present invention generally relates to an electrical switch used for opening and closing an electrically conductive path between an electrical supply and an electrical load. In particular, the present invention relates to a regulated power supply assembly suitable for operating such an electrical switch.
In conventional electrical switches, at least one movable contact is displaced relative to at least one pair of stationary contacts to establish or interrupt an electrically-conductive path between supply-side and load-side stationary contacts. The supply-side and load side stationary contacts are connected to an electrical supply and an electrical load respectively. An electromagnetic assembly is included to provide a driving force such as to cause a desired displacement of the movable contact from an open position to a closed position during a switching-on operation. In addition, a biasing mechanism is included to provide a biasing force to return the movable contact from the closed position to the open position during a switching-off operation.
A typical electromagnetic assembly includes a magnet frame, which includes a stationary portion referred to as 'yoke' and a movable portion referred to as 'armature' (sometimes also referred to as 'anker'). The yoke and the armature have a complementary construction with air gaps in between confronting ends. The armature of the electromagnetic assembly is coupled to the movable contacts, and is held in a spaced relationship from the yoke using the biasing mechanism. The yoke is associated with an electromagnetic coil. During the switching-on operation, the electromagnetic coil is energized through a power supply assembly to establish a magnetic flux through the yoke and consequently, through the armature such that the armature moves under the influence of magnetic force against the biasing force exerted by the biasing mechanism, thereby providing a driving force to displace the movable contact from the open position to the closed position thereof. During the switching-off operation, the power supply assembly de-energizes the electromagnetic coil such that the movable contact returns to the open position under influence of the biasing force exerted by the biasing mechanism.
In various industrial applications, electrical switches are required to handle high electrical loads, with electrical currents ranging from hundreds to even thousands of amperes at correspondingly high electrical voltages.
As well known in the art, electrical switches are prone to arcing between corresponding stationary and movable contacts during each switching operation. Such arcing may cause considerable damage to the contacts. Accordingly, it is important to adopt possible measures to minimize arcing between the contacts during switching operations. Moreover, it is imperative to ensure that even when created, the arc is extinguished as quickly as possible.
In the prior art, one approach adopted to mitigate the problem of arcing and resulting damage to the electrical switch while interrupting an electrical current there through during the switching-off operation is to ensure that movable contacts are separated from corresponding stationary contacts as quickly as possible.
One such solution is known, for example, from US 5,910,890 . The aforementioned patent discloses a control circuit for an electrical switching device which has a set of contacts which are operated by an electromagnetic coil.
The control circuit includes first and second input terminals to receive a control signal for operating the electrical switching device.
A first transistor has a conduction path connected in series with the electromagnetic coil between the first and second control terminals. A controller applies a series of electrical pulses to a control terminal of the first transistor to switch that transistor into a conductive state and apply current pulses to the coil.
A fly-back circuit has a first diode and a second transistor connected in series to provide a conductive path in parallel with the electromagnetic coil for current produced in the electromagnetic coil when the first transistor is nonconductive. The second transistor is biased into a first conductive state by the control signal. Upon removal of the control signal from the first and second input terminals, the second transistor is biased into a second conductive state by current produced in the electromagnetic coil with the second conductive state being less conductive than the first conductive state. Thus the first conductive state acts to maintain an electromagnetic field produced by the coil between occurrences of the electrical pulses. The second conductive state produces a voltage drop in the path for current produced in the electromagnetic coil when it is desired to deactivate the switching device. This action dissipates significant power to rapidly deplete the coil stored magnetic field which results in rapid opening of the switch contacts.
While it is desirable to achieve rapid opening during the switching-off operation to avoid arc formation, uncontrolled opening of the electrical switch in accordance with various state-of-the-art techniques, as also exemplified in the aforementioned patent, suffers from several disadvantages.
During the switching-off operation, when the electromagnetic assembly is de-energized to remove the driving force, the electrical switch transitions from the closed position to the open position under the influence of the biasing force exerted by the biasing mechanism. During this transition, energy imparted to various movable components (mainly the armature and the movable contact) becomes undesirably high such as to engender undesirable mechanical stress therein. Such mechanical stress adversely impacts operational life of the electrical switch. In extreme circumstances, such uncontrolled opening may disadvantageously cause the movable contacts to rebound towards the corresponding stationary contacts, which may undesirably lead to formation of arc between the movable and the stationary contacts. Another example of power supply assembly, which is suitable for use in an electric switch is known from the document EP 1 675 245 A2 . As will now be understood, it is a challenge to ensure that the switching-off operation is carried out in such manner as to satisfy the contradictory requirements of effecting a rapid opening of the electrical switch and yet, reducing mechanical damage caused due to energy imparted to various movable components to achieve the same.
Various prior art electrical switches simply focus on achieving a rapid opening during the switching-off operation without providing any measures to eliminate mechanical damage resulting therefrom.
In light of the above, there is a need for an electrical switch adapted for regulating transition from a closed position to an open position thereof. It is desirable that the electrical switch is adapted to not only ensure rapid separation between corresponding movable and stationary contacts such as to minimize arcing there between while transitioning from the closed position to the open position but energy imparted to various movable components, such as one or more movable contacts, an armature, and so on, within the electrical switch is also regulated to eliminate any mechanical damage thereto.
Accordingly, an object of the present invention is to provide a regulated power supply assembly suitable for use in electrical switches such that transition from a closed position to an open position is effectively regulated and optimized.
The object of the present invention is achieved by regulated power supply assembly suitable for use with an electrical switch according to claim 1, method for providing a regulated power supply suitable for use with an electrical switch according to claim 8, and an electrical switch according to claim 10. Further embodiments of the present invention are addressed in corresponding dependent claims.
An electrical switch includes at least one pair of stationary contacts and at least one movable contact. The electrical switch also includes an electromagnetic assembly which is configured to displace the movable contact between an open position and a closed position thereof.
In a first aspect of the present invention, a regulated power supply assembly suitable for use in an electrical switch is provided.
In a second aspect of the present invention, a method for providing a regulated power supply suitable for use in an electrical switch is provided.
In a third aspect of the present invention, an electrical switch including a regulated power supply assembly recited in the first aspect of the present invention is provided. The regulated power supply assembly is operated in accordance with the second aspect of the present invention as recited herein.
Thus, the present invention provides a regulated power supply assembly suitable for use with an electrical switch, a method for providing a regulated power supply suitable for use with an electrical switch, and an electrical switch comprising said regulated power supply assembly and operated in accordance with said method.
The present invention facilitates effectively regulating transition from a closed position to an open position such that one or more movable contacts are displaced away from corresponding stationary contacts relatively quite rapidly during a first time period. In a second time period, subsequent to the first time period, energy imparted to various movable components is regulated such that a "soft opening" is achieved.
Such effective regulation, in turn, results in eliminating any undue mechanical stress and related adverse affects on performance of the electrical switch over a period of time, thereby increasing an operational life thereof.
The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1: illustrates a schematic view of an electrical switch in accordance with an embodiment of the present invention,
FIG 2: illustrates a schematic view of a regulated power supply assembly in accordance with a first embodiment of the present invention,
FIG 3: illustrates graphical representations of variation of an excitation current, a magnet stroke, and a contact stroke in accordance with an embodiment of the present invention, and
FIG 4: illustrates a schematic view of a regulated power supply assembly in accordance with a second embodiment of the present invention.

Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.
Referring to FIG 1, a schematic view of an electrical switch 100 is provided.
The electrical switch 100 includes a contact assembly 102, an electromagnetic assembly 104, and a regulated power supply assembly 106. It should be noted the electrical switch 100 includes various other components in addition to those shown in the adjoining figure. However, these additional components have not been shown in the adjoining figure for sake of clarity.
The contact assembly 102 includes at least one pair of stationary contacts 108, and corresponding at least one movable contact 110. The movable contact 110 is displaceable between an open position and a closed position such that the relative separation 'G' between the stationary contacts 108 and the movable contact 110 is altered between a maximum value (open position) and zero (closed position). In the closed position, the movable contact 110 establishes an electrical flow path between the stationary contacts in a bridge-like manner.
The electromagnetic assembly 104 includes a yoke 112, an armature 114, and an electromagnetic coil 116. As shown in the adjoining figure, the electromagnetic assembly 104 is operably coupled to the movable contact 110, and is configured to displace the movable contact 110 between the open position and the closed position thereof. In particular, the electromagnetic assembly 104 is configured for providing a driving force such as to cause a desired displacement of the movable contact from the open position to the closed position during a switching-on operation; the electromagnetic assembly 104 is also configured for providing a holding force to the movable contact 110 during the closed position thereof. In addition, a biasing mechanism (not shown) is included in the electrical switch 100 to provide a biasing force to return the movable contact 110 from the closed position to the open position during a switching-off operation.
During the switching-on operation, the electromagnetic coil 116 is energized to establish a magnetic flux through the yoke 112 and consequently, through the armature 114 such that the armature 114 moves under the influence of magnetic force against the biasing force. The armature 114 is coupled to the movable contact 110 and hence, provides a driving force to displace the movable contact 110 from the open position to the closed position thereof. The movement of the armature 114 is characterized in terms of "magnet stroke" which is the distance traversed by the armature 114 and ranges from a value M=0 in the open position to a value M=M(max) in the closed position. At the same time, the position of movable contact 110 is characterized in terms of "contact stroke" which is the distance traversed by the movable contact 110 relative to the open position thereof and ranges from a value C=0 in the open position to a value C=C(max) in the closed position.
Subsequently, the electromagnetic assembly 104 continues to provide the driving force (preferably relatively reduced) to maintain the closed position of the movable contact 110.
During the switching-off operation, the electromagnetic coil 116 is de-energized such that the movable contact 110 returns to the open position under influence of the biasing force exerted by the biasing mechanism.
The operation of the electrical switch 100, as described in the foregoing description, is generally known in the art.
In accordance with various techniques of the present invention, the regulated power supply assembly 106 is used to regulate the excitation current provided to the electromagnetic assembly 104 such that transition of the movable contact 110 from the closed position to the open position is effectively regulated. The regulated power supply assembly 106 will now be described in detail in conjunction with FIGS 2 through 4.
Referring now to FIG 2, a schematic view of the regulated power supply assembly 106 is shown in accordance with a first embodiment of the present invention.
The regulated power supply assembly 106 includes rectification means 204, switching means 206, free-wheeling means 208, and controlling means 210.
The regulated power supply assembly 106 also includes a pair of input terminals T1, T2 and a pair of output terminals T3, T4. The input terminals T1, T2 are configured to be connected to a driving source 202 such that an input voltage Vin is applied across the input terminals T1, T2. Similarly, the output terminals T3, T4 are configured to be connected to the electromagnetic assembly 104 such that an output voltage Vout is applied across the electromagnetic assembly 104, thereby, providing an excitation current thereto.
The driving source 202 provides required power supply for generating excitation current in the electromagnetic assembly 104. The driving source 202 may be a voltage source or a current source.
The switching means 206 are connected in series to the electromagnetic assembly 104. The free-wheeling means 208 connected in parallel to said electromagnetic assembly 104. The controlling means 210 are operatively coupled to the input terminals T1, T2, the switching means 206, and the free-wheeling means 208.
According to the embodiment shown in the adjoining figure, the input terminals T1, T2 are connected to the rectification means 204. Thus, the input voltage Vin is applied to the rectification means 204. The rectification means 204 facilitate achieving a unidirectional voltage. In one example, the rectification means 204 include a full-wave rectification circuit such as a bridge rectifier. The output from the rectification means 204 is connected to the output terminals T3, T4 through a series connection of the switching means 206, as shown. The output terminals T3, T4 are connected to the electromagnetic assembly 104.
As will now be understood, the rectification means 204 are configured for receiving an input voltage Vin across the input terminals T1, T2, and generating an output voltage Vout therefrom across the output terminals T3, T4, which are connected to the electromagnetic assembly 104 for providing the excitation current thereto.
The rectification means 204 advantageously enable the regulated power supply assembly 106 to be operated using an alternating-current based as well as a direct-current based driving source 202.
It should be noted that in accordance with various techniques of the present invention, the rectification means 204 are optional. Accordingly, in an alternative embodiment of the present invention, as will be described later in conjunction with FIG 4, the rectification means 204 are not provided in case the driving source 202 is known to be based on direct-current supply.
The switching means 206 are configured for switching between a high-impedance mode and a low-impedance mode for regulating the excitation current through the electromagnetic assembly 104. The switching means 206 are operated based on a switching control signal received from the controlling means 210.
In an exemplary embodiment of the present invention, a transistor Q1 is used to implement the switching means 206. The switching control signal (CS) is applied to gate terminal of the transistor Q1, while a current path is established from the source to the drain of the transistor Q1.
When the transistor Q1 is switched-on, a low-impedance current flow path is established through the transistor Q1. On the other hand, when the transistor Q2 is switched-off, a high-impedance current flow path is established through Q1, effectively preventing flow of current there through. Thus, the switching means 206 are operable in one of a high-impedance mode and a low-impedance mode based on a switching control signal received from the controlling means 210.
The free-wheeling means 208 are operable in one of a high-impedance mode and a low-impedance mode, and are configured for providing a free-wheeling current flow path for the excitation current. The free-wheeling means 208 are connected across the output terminals T3, T4. Thus, the free-wheeling means 208 are effectively coupled in parallel to the electromagnetic assembly 104 and therefore, provide a free-wheeling current flow path for the excitation current. The free-wheeling means 208 are operated based on a free-wheeling control signal received from the controlling means 210.
In an exemplary embodiment of the present invention, the free-wheeling means 208 include a transistor Q2, a diode D connected in series with the transistor Q2, and a varistor VAR connected across the source and the drain of the transistor Q2. The free-wheeling control signal (CF) is applied to the gate of transistor Q2. It should be noted that in various alternative embodiments of the present invention, the varistor VAR may be replaced with similar variable impedance components such as a Zener diode or a Transient Voltage Supressor (TVS).
When the transistor Q2 is switched-on, a low-impedance free-wheeling current flow path is established through the transistor Q2 and the diode D. On the other hand, when the transistor Q2 is switched-off, a high-impedance free-wheeling current flow path is established through the varistor VAR and the diode D. Thus, the free-wheeling means 208 are operable in one of a high-impedance mode and a low-impedance mode based on a free-wheeling control signal received from the controlling means 210.
The controlling means 210 provide the switching control signal to control the switching means 206. Additionally, the controlling means provide the free-wheeling control signal to control the free-wheeling means 208. In an exemplary embodiment of the present invention, the controlling means 210 are implemented using a microcontroller.
The operation of the regulated power supply assembly 106, described in conjunction with FIG 2 above, will now be explained in detail in conjunction with FIG 3.
FIG 3 illustrates graphical representations of variation of an excitation current (Curve I), a magnet stroke (Curve II), and a contact stroke (Curve III) during transition of the electrical switch 100 from the closed position to the open position in accordance with an embodiment of the present invention.
Curve I shows the variation of the excitation current flowing through the electromagnetic assembly 104 during transition of the electrical switch 100 from the closed position to the open position between time instants t1 and t5. The excitation current is at a steady-state value (Iss) in the closed position of the electrical switch 100 between time instants t0 and t1. At time instant t1 the transition from the closed position is initiated. The electrical switch 100 achieves the open position at t5.
Curves II and Curve III respectively show the variation of magnet stroke from M(max) to 0 and the variation of contact stroke from C(max) to 0 between time instants t1 and t5.
During operation of the regulated power supply assembly 106, the controlling means 210 samples the input voltage Vin applied across input terminals T1, T2 through a sampled signal SS.
When the input voltage Vin is applied across input terminals T1, T2 (for example, through closing a switch S, shown in FIG 2), the controlling means 210 trigger a switching-on operation whereby the movable contact 110 transitions from the open position to the closed position.
In the closed position, between time instants t0 to t1, the controlling means 210 regulate the switching means 206 and the free-wheeling means 208. In the exemplary embodiment depicted in the adjoining figure, the controlling means 210 are such that the switching control signal is a pulse-width modulated signal. When the switching control signal is applied to the switching means 206, during an 'ON' period of the switching control signal, the excitation current flows through the transistor Q1 whereas during an 'OFF' period of the switching control signal, the free-wheeling means 208 provide the free-wheeling current flow path to maintain continuity of current and avoid sudden voltage surges and other undesirable effects due to sudden breakage of excitation current in the electromagnetic coil 116.
When the voltage difference across the input terminals T1, T2 subceeds a predefined threshold value (that is, the voltage difference is below the predefined threshold value), the controlling means 210 initiate transition of the electrical switch 100 from the closed position to the open position at time instant t1. In one example, the driving source 202 at input terminals T1, T2 is disconnected through opening the switch S.
In an alternative embodiment of the present invention, the switch S is implemented using a coupling transistor, and the controlling means 210 may be operationally coupled to the switch S, such that when the voltage difference across the input terminals T1, T2 subceeds the predefined threshold value, the controlling means 210 switch-off the coupling transistor such as to isolate the driving source 202.
During transition from the closed position to the open position, it is desirable that the excitation current in the electromagnetic assembly 104, and in particular, the electromagnetic coil 116, initially, decays at a relatively faster rate, and eventually, starts decaying at a relatively slower rate.
Accordingly, during a first time period during transition from the closed position to the open position, the controlling means 210 operate each of the switching means 206 and the free-wheeling means 208 in respective the high-impedance mode. When switching means 206 operate in the high impedance mode, the flow of current there through is effectively blocked. As the free-wheeling means 208 are also operating in the high-impedance mode, the flow of current through the transistor Q2 is also effectively blocked, and hence, the excitation current is forced to flow through the varistor VAR and the diode D. Accordingly, the excitation current starts to decay at a fast rate, as seen in region 'b' in curve I.
At time instant t2, the armature 114 starts moving away from the yoke 112, accordingly, the magnet stroke starts decreasing, as depicted in region 'c' in Curve II. As the armature 114 moves away from the yoke 112, the excitation current starts rising due to electromagnetic induction, as seen in region 'c' in Curve I.
Eventually, at time instant t3, the movable contact 110 loses contact with the corresponding stationary contacts 108. The movable contact 110 recedes away from the stationary contacts 108, as depicted in region 'd' in Curve III.
At time instant t4, when the movable contact 110 has gained sufficient displacement or velocity relative to the stationary contacts 108, the controlling means 210 start operating at least one of the switching means 206 and the free-wheeling means 208 in respective the low-impedance mode. Thus, during a second time period between time instants t4 and t5, at least one of the switching means 206 and the free-wheeling means 208 operates in the low impedance mode. Therefore, the excitation current starts to decay at a relatively slower rate, as indicated in region 'e' in Curve I.
According to an advantageous technique of the present invention, the switching means 206 are operated in the low impedance mode only if the input voltage Vin across the input terminals T1, T2 is exactly zero. In case the input voltage Vin is below the predefined threshold value but has a non-zero value, the switching means 206 are operated in the high impedance mode and the free-wheeling means 208 are operated in the low impedance mode.
In case the switching means 206 are operated in the low-impedance mode, the excitation current free-wheels through the transistor Q1 and the rectification means 204. In case the free-wheeling means 208 are operated in the low-impedance mode, the excitation current free-wheels through the transistor Q2 and the diode D.
The excitation current in the electromagnetic coil 116 between time instants t4 and t5 exerts a braking force on the armature 114 and hence, serves to slow down the movable contact 110 and other movable components such as to achieve a "soft opening" in the electrical switch 100.
Thus, the controlling means 210 are configured for operating each of the switching means 206 and the free-wheeling means 208 in respective the high-impedance mode during a first time period between time instants t1 and t4 during transition from the closed position to the open position. Further, the controlling means 210 operate at least one of the switching means 206 and the free-wheeling means 208 in respective the low-impedance mode during a second time period during transition from the closed position to the open position.
The first time period begins at a time instant (t1) at which transition from the closed position to the open position is initiated and ends at a time instant (t4) at which the movable contact (110) acquires a predefined velocity and/or a predefined displacement relative to the stationary contacts (108). The second time period begins at the time instant (t4) and ends at a time instant (t5) at which the movable contact (110) acquires the open position.
It should be noted that the first and the second time periods may be configured as desired. In one embodiment of the present invention, the first and the second time periods are pre-configured in the controlling means 210. In an alternative embodiment of the present invention, the controlling means 210 may determine the first and the second time periods based on directly determining position and/or velocity of the movable contact 110 (and/or the armature 114) with respect to the stationary contacts 108 (and/or yoke 112) using suitable sensing modalities. Such sensing modalities for determining position and/or velocity of one or more movable components in the electrical switch 100 are generally known in the art and hence, not being described herein in detail.
Furthermore, during the second time period, the switching means 206 and/or the free-wheeling means 208 may be altered between respective high and low impedance modes to better regulate the transition from the closed position to the open position. Towards this end, the controlling means 210 may be configured to provide a pulse-width modulated signal to the switching means 206 and/or the free-wheeling means 208.
Referring now to FIG 4, a schematic view of the regulated power supply assembly 106 is depicted in accordance with a second embodiment of the present invention.
Various components of the regulated power supply assembly 106 in the second embodiment are same as those of the regulated power supply assembly 106 in the first embodiment of the present invention, as described in conjunction with FIG 2; except that in the second embodiment the rectification means 204 are not included.
In this embodiment, the input terminals T1, T2 are directly connected (that is, without the rectification means 204) to the output terminals T3, T4 through the series connection of the switching means 206.
In accordance with the second embodiment of the present invention, the controlling means 210 operate the switching means 206 in the high-impedance mode during transition from the closed position to the open position from time instants t1 to t5. Further, the controlling means 210 operate the free-wheeling means 208 in the high-impedance mode during a first time period between time instants t1 and t4, and in the low-impedance mode during a second time period between time instants t4 and t5 during transition from the closed position to the open position.
As will be apparent from the preceding description, the operation of the regulated power supply assembly 106 in the second embodiment is essentially similar to that in the first embodiment with the only difference that during the second time period between time instants t4 and t5, only free-wheeling means 208 may be operated in the low-impedance mode. This follows directly from the absence of the rectification means 204 in the regulated power supply assembly 106 in accordance with the second embodiment of the present invention.
Various other technical features described for the first embodiment are applicable for the second embodiment of the present invention.
As will now be understood in light of the description provided herein, the present invention facilitates effectively regulating the transition from the closed position to the open position through controlling excitation current in the electromagnetic assembly. Therefore, the present invention optimizes energy of the movable contact and associated movable components during the opening operation.
Such effective control in turn, results in eliminating undue mechanical stress and related adverse affects on performance over a period of time, thereby increasing an operational life of the electrical switch.
The scope of the present invention is indicated by the following claims.

Claims

A regulated power supply assembly (106) suitable for use in an electrical switch (100), said electrical switch (100) comprising at least one pair of stationary contacts (108), at least one movable contact (110), and an electromagnetic assembly (104) configured to displace said movable contact (110) between an open position and a closed position thereof, said regulated power supply assembly (106) comprising:
- switching means (206) connected in series to said electromagnetic assembly (104),

- free-wheeling means (208) connected in parallel to said electromagnetic assembly (104), and

- controlling means (210) coupled to the switching means (206) and the free-wheeling means (208), characterized in that the controlling means (210) is capable of operating said switching means (206) and said freewheeling means (208) in a high-impedance mode for a first time period during transition of the electrical switch (100) from a closed position to an open position, and operating one of said switching means (206) and said free-wheeling means (208) in a low-impedance mode for a second time period during transition of the electrical switch (100) from said closed position to said open position.
The regulated power supply assembly (106) according to claim 1 further comprising a pair of input terminals (T1, T2) configured to be connected to a driving source (202), and further comprising a pair of output terminals (T3, T4) configured to be connected to said electromagnetic assembly (104) for providing said excitation current thereto.
The regulated power supply assembly (106) according to claim 2 further comprising rectifying means (204) configured for receiving an input voltage (Vin) across said input terminals (T1, T2), and generating an output voltage (Vout) therefrom across said output terminals (T3, T4).
The regulated power supply assembly (106) according to any of the preceding claims, wherein said switching means (206) comprise a transistor (Q1).
The regulated power supply assembly (106) according to any of the preceding claims, wherein said free-wheeling means (208) comprise a transistor (Q2), a diode (D), and a varistor (VAR), wherein said diode (D) is connected in series to said transistor (Q2) and said varistor (VAR) is connected in parallel to said transistor (Q2).
The regulated power supply assembly (106) according to any of claims 2 to 5, wherein said controlling means (210) are configured for sampling a voltage difference across said input terminals (T1, T2), and initiating transition of the electrical switch (100) from said closed position to said open position when said voltage difference subceeds a predefined threshold value.
The regulated power supply assembly (106) according to any of the preceding claims, wherein said first time period begins at a time instant (t1) at which transition of the electrical switch (100) from said closed position to said open position is initiated and ends at a time instant (t4) at which said movable contact (110) acquires a predefined velocity and/or a predefined displacement relative to said stationary contacts (108), and wherein said second time period begins at said time instant (t4) and ends at a time instant (t5) at which said movable contact (110) acquires said open position.
A method for providing a regulated power supply suitable for use in an electrical switch (100), said electrical switch (100) comprising at least one pair of stationary contacts (108), at least one movable contact (110), and an electromagnetic assembly (104) configured to displace said movable contact (110) between an open position and a closed position thereof, said method comprising:
- providing switching means (206) adapted for connecting in series to said electromagnetic assembly (104) and configured for switching between a high-impedance mode and a low-impedance mode for regulating an excitation current through said electromagnetic assembly (104),

- providing free-wheeling means (208) adapted for connecting in parallel to said electromagnetic assembly (104) for providing a free-wheeling current flow path for said excitation current, wherein said free-wheeling means (208) are operable in one of a high-impedance mode and a low-impedance mode,

- operating said switching means (206) and said free-wheeling means (208) in said high-impedance mode for a first time period during transition of the electrical switch (100) from a closed position to an open position, and

- operating one of said switching means (206) and said free-wheeling means (208) in a low-impedance mode during a second time period during transition of the electric switch (100) from said closed position to said open position.
The method according to claim 8, wherein said first time period begins at a time instant (t1) at which transition from said closed position to said open position is initiated and ends at a time instant (t4) at which said movable contact (110) acquires a predefined velocity and/or a predefined displacement relative to said stationary contacts (108), and wherein said second time period begins at said time instant (t4) and ends at a time instant (t5) at which said movable contact (110) acquires said open position.
An electrical switch (100) comprising a regulated power supply assembly (106) in accordance with any of claims 1 to 7, wherein said regulated power supply assembly (106) is operated in accordance with any of claims 8 and 9.