GB2637358A

GB2637358A - Health monitoring of electromagnetic relay

Info

Publication number: GB2637358A
Application number: GB2403256.7A
Authority: GB
Inventors: Vilas Harlapur Vishakha; Bartonek Michael; Raosaheb Jagadale Ramesh
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2024-01-19
Filing date: 2024-03-06
Publication date: 2025-07-23
Also published as: GB202403256D0

Abstract

An EM relay 1 comprises an EM drive unit 2, a fixed contact 7, and a rotatable contact 8. The drive unit comprises a rotatable armature 3 having a first magnetic contact region 5, a yoke 4 having a second magnetic contact region 6, and at least one coil 21 wound around the yoke. In a first state of the relay, the first and second magnetic contact regions are in contact with each other. The rotatable contact is coupled to the rotatable armature and is in contact with the fixed contact in the first state of the relay. When a current flows through the coil, the armature is caused to rotate to a second state of the relay in which the contacts and the magnetic contact regions are separated. The relay further comprises a means for measuring a voltage across the coil and a means for determining a status of the relay based on one or more characteristics of the measured voltage, which may indicate a fault condition or a health of the drive unit. The fault condition may indicate armature rotation without application of current through the coil, or application of current through the coil with insufficient or no rotation of the armature.

Description

Health Monitoring of Electromagnetic Relay Field

This relates to health monitoring of an electromagnetic relay. In particular; this relates to a feature of the electromagnetic relay for determining a fault condition and/or a health of the relay.

Background

Electromagnetic relays are well known and part of lots of electric devices. Even in devices with semiconductor switching elements, classic mechanical relays have the advantage of lower resistance and lower dissipated energy.

Electromagnetic relays are often included as part of so called hybrid switchgears, especially hybrid circuit breakers (NCB). Hybrid switchgears contain a semiconductor switching unit and a bypass relay (comprising said electromagnetic relay). In normal operation, the contacts of the bypass relay are closed and the semiconductor switching unit is typically in a non-conductive mode. It is also possible that the semiconductor switching unit is in a conductive or a semi-conductive mode, The current passing the switchgear flows through the low resistance bypass relay. In case of a short circuit, the bypass relay opens its contacts as fast as possible to commute the current to the semiconductor switching unit and thereby open the circuit breaker.

It is therefore important that the bypass relay operates correctly. Moreover, it is important that any unintended opening/closing of the bypass relay is avoided, since this could damage the semiconductor switching circuit and pose a potential threat to life and property in the situation where the contacts close during short circuit condition. To this end, it is desirable to ascertain a state of an electromagnetic relay during operation to determine the health of the relay and/or to be able to detect a fault: condition of the relay.

Summary

Disclosed herein is an electromagnetic relay and a system comprising the electromagnetic relay. A hybrid circuit breaker is also disclosed.

An electromagnetic relay comprises an electromagnetic drive unit comprising a rotatable armature having a first magnetic contact region and a yoke having a second magnetic contact region, the first magnetic contact region being in physical contact -2 -with the second magnetic contact region in a first state of the relay. The relay also comprises a fixed electrical conductor, and a rotatable electrical conductor coupled to the rotatable armature, the rotatable electrical conductor configured to be in electrical contact with the fixed electrical conductor in the first state of the relay. The rotatable 0 electrical conductor can be understood to be coupled such that they rotate together.

Optionally the electrical conductor is rigidly coupled to the armature in some example. Optionally, they are coupled along a common shaft or axis. Optionally the shaft is a torsional spring or torque rod. The torsional spring (which may be optionally implemented as a blade spring) can act to bias the rotatable electrical conductor in towards the open state of the relay, so as to facilitate quicker breaking of the circuit.

The electromagnetic drive unit further comprises at least one coil wound at least in part around a portion of the yoke. The electromagnetic drive unit is configured to apply a current through the at least one coil to cause the armature to rotate to a second state of the relay, wherein in the second state of the relay the rotatable electrical conductor is not in electrical contact with the fixed electrical conductor and the first magnetic contact region is not in physical contact with the second magnetic contact region. The relay also comprises means for measuring a voltage across the at least one coil and means for determining a status of the electromagnetic relay based on the measured voltage.

In other words, it has been recognised that the voltage measured across the coil can provide information about the operation and status of the relay, without the need for external power supplies. In particular, the principles of electromagnetic induction can be used to ascertain how the relay is operating. The status of the electromagnetic relay can indicate a fault condition and/or a health of the electromagnetic drive unit. The fault condition can be indicative of rotation of the armature without application of the current through the at least one coil (for example, due to vibrations or degradation of the magnets holding the armature in place, which degradation can occur naturally over time and/or due to environmental factors). The fault condition can be indicative of application of the current through the at least one coil without rotation of the armature (for example, due to failure or a fault in the electromagnetic drive unit). A more robust relay may therefore be provided.

In some examples, the means for determining a status can comprise means for determining, based on one or more characteristics of the measured voltage, a status of the electromagnetic relay. The one or more characteristics can include one or more of: an amplitude of a detected peak in the measured voltage, a duration of the detected peak, a polarity of the measured voltage, a gradient of a voltage-time curve for the measured voltage, and/or a dip in the voltage-time curve. In other examples, the means for determining a status can comprise means for detecting a peak in the measured voltage means for determining, based on one or more characteristics of the detected peak, the status of the electromagnetic relay.

In some examples, the electromagnetic drive unit comprises a capacitor and is configured to cause the capacitor to discharge to apply the current through the at least one coil. In such examples, the fault condition can he indicative of rotation of the armature without discharge of the capacitor, or can he indicative of discharge of the capacitor without rotation of the armature, or can be indicative of rotation of the armature being below a threshold speed (i.e. the rotation of the armature is slower than expected). In other examples, the health of the electromagnetic drive unit can indicate a health of the capacitor and/or the capacitor circuit.

In some examples, the at least one coil comprises a first coil, and the electromagnetic drive unit is configured to apply the current through the first coil to cause the armature to rotate. In other examples, the at least one coil comprises a first coil and a second coil, the first coil disposed around the second coil, and the electromagnetic drive unit is configured to apply the current through the second coil to cause the armature to rotate. The means for measuring are configured to measure the voltage across the first coil. In other words, the voltage can be measured across the driving coil and/or across an auxiliary coil disposed around the driving coil.

In some examples, the rotatable armature comprises a third magnetic contact region opposite the first magnetic contact region, and the yoke comprises a fourth magnetic contact region, the third magnetic contact region being in physical contact with the fourth magnetic contact region in the first state of the relay. The at least one coil further comprises an additional coil wound at least in part around an additional portion of the yoke. The means for measuring a voltage across the at least one coil comprise means for measuring the voltage across the additional coil. In other words, the voltage can be measured across multiple coils, and the voltage signals from the multiple coils can be combined or analysed separately to determine a status of the relay.

In some examples, the voltage measurement can be taken at the ends of two or more coils connected in series, leading to a single combined voltage signal when the armature moves. In other examples, the voltage is measured across two or more coils separately; by using e.g. two separate coils, which result in two time varying magnetic fields when the relay is operated, two distinct voltage signals can be determined when the armature moves.

Optionally, one or more additional electric contact elements are provided, which define an auxiliary electric path when the relay is in the second state. The current on the auxiliary electrical path provides an indication that the required gap between electric contacts is achieved in the open (second) state of the relay. The electric contact elements can optionally be implemented as one or more biasing members, which are configured to bias the rotatable electrical conductor towards its position in the first (closed) state of the relay. The biasing members can be configured to urge the electrical conductor into electrical contact with the fixed electrical conductor. In this way, contact pressure between the rotatable electric conductor and the additional electric contact elements can be improved., and the biasing members can assist the electromagnetic drive unit to close the relay. Optionally, the biasing members are springs. Optionally, the biasing members are leaf springs.

Optionally, the yoke comprises a further magnetic contact region on an opposite side of the second magnetic contact region. The armature can be configured such that the first magnetic contact region is in physical contact with the further magnetic contact region in the second state of the relay. In this way, the relay is bistabie, i.e. stable in both an "on" state in which there is electrical current flowing through a current conduction path defined through the fixed and rotatable conductors (first state) and an "off" state in which no current flows along said path (second state).

In this implementation of the relay, the determination of the status can be made at or by the relay itself. The means for measuring a voltage across the at least one coil can comprise a voltage probe and/or the means for determining a status of the electromagnetic relay can comprise a PCB. For example, the relay may comprise the voltage probe, PCB and associated electronics. The relay can comprise means for outputting an alert or notification based on the determined status. For example, an alert may be output to an operator of the relay and/or at a device comprising or incorporating the relay.

as Also disclosed herein is a hybrid circuit breaker comprising a semiconductor switching unit and a bypass relay arranged in parallel to the semiconductor switching unit, wherein the bypass relay comprises the electromagnetic relay described above.

Also disclosed herein is system, comprising a computing device and an electromagnetic relay. The relay comprises an electromagnetic drive unit comprising a rotatable armature having a first magnetic contact region, and a yoke having a second magnetic contact region, the first magnetic contact region being in physical contact 0 with the second magnetic contact region in a first state of the relay. The relay comprises a fixed electrical conductor, and a rotatable electrical conductor coupled to the rotatable armature, the rotatable electrical conductor configured to be in electrical contact with the fixed electrical conductor in the first state of the relay. The electromagnetic drive unit further comprises at least one coil wound at least in part io around a portion of the yoke, the electromagnetic drive unit configured to apply a current through the at least one coil to cause the armature to rotate to a second state of the relay, wherein in the second state of the relay the rotatable electrical conductor is not in electrical contact with the fixed electrical conductor and the first magnetic contact region is not in physical contact with the second magnetic contact region. The relay comprises means for measuring a voltage across the at least one coil.

The computing device of the system comprises means for determining, based on the measured voltage, a status of the electromagnetic relay. In other words, in this implementation of the relay; the determination of the status can be made at a computing device remote from, or external to, the relay itself. The computing device can be any suitable computer or processing unit. The system may be implemented as a circuit breaker or hybrid circuit breaker, for example, or the computing device may be remote from a device incorporating the relay.

The relay can comprise means for outputting the measured voltage using wired or wireless communication protocols. The computing device can comprise means for receiving the output measured voltage. The computing device can comprise means for outputting an alert or notification based on the determined status. For example, an alert may be output to an operator of the relay and/or at a device comprising or incorporating the relay.

In other words, it has been recognised that the voltage measured across the coil can provide information about the operation and status of the relay, without the need for external power supplies at the relay. In particular, the principles of electromagnetic induction can be used to ascertain how the relay is operating. The status of the electromagnetic relay can indicate a fault condition and/or a health of the electromagnetic drive unit. The fault condition can be indicative of rotation of the armature without application of the current through the at least one coil (for example, due to vibrations or manual opening/closing of the relay). The fault condition can be indicative of application of the current through the at least one coil without (or with slower than expected) rotation of the armature (for example, due to failure or a fault in the electromagnetic drive unit). A more robust relay may therefore be provided.

In some examples, the means for determining a status can comprise means for determining, based on one or more characteristics of the measured voltage, a status of the electromagnetic relay. The one or more characteristics can include one or more of: an amplitude of a detected peak in the measured voltage., a duration of the detected peak, a polarity of the measured voltage, a gradient of a voltage-time curve for the measured voltage, and/or a dip in the voltage-time curve. In other examples, the means for determining a status can comprise means for detecting a peak in the measured voltage means for determining, based on one or more characteristics of the detected peak, the status of the electromagnetic relay.

In some examples, the electromagnetic drive unit comprises a capacitor and is configured to cause the capacitor to discharge to apply the current through the at least one coil. In such examples, the fault condition can be indicative of rotation of the armature without discharge of the capacitor, or can be indicative of discharge of the capacitor without (or with slow, i.e. below a threshold speed) rotation of the armature. In other examples, the health of the electromagnetic drive unit can indicate a health of the capacitor and/or the capacitor circuit.

The system can be considered an alternative solution to an electromagnetic relay wil internal determination means. Any of the examples described above with respect to the relay can be implemented in the system described herein.

In some examples of the relay and/or system, the means for determining a status of the electromagnetic relay comprises a one or more processors and a computer program comprising instructions for causing the one or more processors to perform at least the steps of determining, based on the measured voltage, a status of the electromagnetic relay. In some examples, the means for determining comprises a computer-readable medium (such as a non-transitory computer-readable medium) comprising program instructions stored thereon for determining, based on the :35 measured voltage, a status of the electromagnetic relay. In some examples, the means for determining comprises a determining module configured to determine, based on the measured voltage, a status of the electromagnetic relay. -7 -

List of Figures The detailed description is with reference to the following fiCIUMS. Like reference numerals refer to like figures.

Figure 1 shows a first side of an electromagnetic relay in a first state; Figure 2 shows an opposite, second, side of the electromagnetic relay of Figure 1 in the first state; Figure 3 shows the first side of the electromagnetic relay in a second state; Figure 4 shows the second side of the electromagnetic relay of Figure 3 in the second state; io Figure 5a shows a schematic block diagram of a first example of the relay; Figure 5b shows a schematic block diagram of a second example of the relay, where the relay is part of a system which performs the determining; Figures 6a, 6b show example experimental data (voltage against time) of a first example of determining a status of the relay; Figures la, lb show example experimental data (voltage against time) first example of determining a status of the relay; and Figures 8,a, 8b show example experimental data (voltage anainst time) of a first example of determining a status of the relay.

Detailed description

With reference to Figures 1 and 2, an example electromagnetic relay 1. is described, the relay arranged in a first state. Figures 1 and 2 show opposite sides of the relay. Figures 3 and 4 show opposite sides of the relay 1 in a second state.

As seen in Figure 1, the relay 1 comprises an electromagnetic drive unit 2 with a rotatable armature 3 and a yoke 4. The armature 3 comprises a first magnetic contact region 5 on a First arm; and the yoke 4 comprises a second magnetic contact region 6, the first magnetic contact region S being in physical contact with the second magnetic contact region 6 in the first state of the relay 1.

The electromagnetic drive unit 2 further comprises a coil 21, which is wound at least in part around a portion of the yoke 4. The electromagnetic drive unit 2 further comprises at least a first permanent magnet 23, which is arranged between two pares of the yoke 4. When the drive unit 2 applies a current through the coil 21, the as resulting magnetic field overcomes the force between the first 5 and second 6 magnetic regions caused by the permanent magnet 23 and cases the armature to rotate towards a second state (discussed further with reference to Figures 3 and 4).

As seen in Figure 2, the relay 1 further comprises at least a first, fixed (immovable), electrical conductor or contact 7 and a rotatable electrical conductor 8 with a second electric contact 9 at one end. The first fixed electrical conductor 7 contacts the second electric contact 9 of the rotatable conductor 8 in the first state of the relay. The fixed contact 7 is arranged on a first contact piece 25, which comprises at least one opening or a soldering log for external connecting to a circuit or current line.

The armature 3 and the conductor 8 are arranged together on a shaft 10 (which extends into the page) and are offset from each other along the axis of the shaft 10. Therefore, rotation of the armature by the drive unit 2 causes a corresponding rotation of the rotatable conductor, such that in the second state of the relay the rotatable electrical conductor 8 is not in electrical contact with the fixed electrical conductor 7.

In this particular (non-limiting) example, it can be seen that; the armature 3 comprises a second arm, with the second arm comprising a third magnetic contact region 16. Optionally the armature 3 is essentially symmetric. In this example; the yoke 4 also comprises a fourth magnetic contact region 17. In the first state, the third 16 and fourth 17 magnetic contact regions are in physical contact. The yoke 4 can also comprise a further magnetic contact region on an opposite side of the second magnetic contact region 6; called herein the fifth magnetic contact region 27; the first magnetic contact region 5 can be arranged on both sides of the first arm of the armature 3 such that the first magnetic contact region 5 is in touch with the fifth magnetic contact region 27 in the second state of the relay (see Figure 3). Similarly, the yoke 4 can comprise a sixth magnetic contact region 28 where, in the second state, the third magnetic contact region 16 is in touch with the sixth magnetic contact region 28 (see Figure 3).

Moreover, the electromagnetic drive unit 2 further comprises an additional coil 22, wound at least in part around an additional portion of the yoke 4, and a second permanent magnet 24; which is also arranged between two parts of the yoke 4. When the drive unit 2 applies a current through the coil 22, the resulting magnetic field causes the armature to rotate towards the second state, The relay 1 is therefore able to be in two different stable states. In such examples, as shown in Figures 1 to 4, the arrangement comprising the yoke 4, the first and additional coil 21., 22 and the first :35 and second permanent magnet 23, 24 is essentially symmetrical.

As also seen in Figure 2; in this non-limiting example, the rotatable electrical conductor 8 is substantially symmetric and comprises a third electric contact 14 to contact a fixed fourth electric contact 15 of the relay 1. The immovable/fixed fourth electric contact 15 is arranged on a second contact piece 26, comprising at least one opening or a soldering log for external connecting. Such a rotatable conductor provides a double contact making or breaking, and is also called a contact bridge. All the electric contacts are embodied here as switching contacts. In the first state, as shown in Figure 2, a current path is defined through the electric contacts 7, 9, 14, 15. In other words, a current conduction path is defined through the fixed and rotatable conductors, and an electric current flow through the relay 1 is enabled. This is a switched "on" state.

The second state, as shown in Figure 4, is a switched "off" state. In this state the electric contacts 7, 9, 14, 15 are opened or separated, and an electric current flow through the relay 1 is disabled/prevented. The switching of the conductors is driven by the rotation of the armature 3 to the second state of the relay, shown in Figure 3.

The shaft 10 which couples or connects the rotatable contact 8 and the armature 3 can be any suitable form. Optionally, the shaft. 10 is embodied as torsional element 11. Optionally the shaft 10 is embodied as torsional spring 12. This is a simple embodiment of the torsional element 11, Other terms for the torsional spring 12 are torsion spring or torsion bar or torque rod. Optionally the torsional spring 12 is embodied as a flat spring 13. However, the shaft 10 can be formed according any material or form or comprising any cross-section.

The torsional element 11 is preferably flexible enough to compensate for small changes in position and/or dimension of the magnetic contact regions 5, 6, 16, 17, 27, 28 and/or the electric contacts 7, 9, 14, 15; in this way, the magnetic contact regions 5, 6, 16, 17, 27, 28 can by in physical contact without an air gap (reducing power requirements for the coils 21, 22 of the electromagnetic drive unit 2 in the event of switching), and the electric contact areas 7, 9, 14, 15 can be connected with sufficient contact pressure (reducing resistance in the circuit). As this compensation is only needed in one direction of rotation, it is further possible to design the torsional element 11 to connect the armature to the conductor 8 in such a way that the connection is rigid in the opposite direction of rotation (i.e. in the direction intended to open the electric contacts 7, 9, 14, 15). This can increase the speed of opening of the :35 relay. Operation of the relay may therefore be improved.

Optionally, as shown in Figures 2 and 4, the relay 1 further comprises one or more biasing members 19, 20. In some examples, the biasing members can be implemented as leaf springs. he biasing members 19, 20 bias the electrical conductor 8 towards contact with the first electric contact 7, i.e. bias the relay to a "closed" or "on" state. The biasing members 19, 20 further support the electromagnetic drive unit 2 in bringing the contact arm 8 from the second state to the first state. In some particular examples, the relay 1 comprises an auxiliary electrical path from the first auxiliary contact piece 31 to the second auxiliary contact piece 32. The auxiliary electric path comprises the biasing members 19, 20, which are here also electric contact elements. When the relay is in the second (open) state, the current on the auxiliary electrical path indicates that the desired gap is achieved between the electric contacts 7, 9, 14, 15.

It has been recognised that the manner by which the relay operates -application of current to the coil(s), generation of magnetic field, resulting rotation of the armature 3 -can be used to ascertain information about the state of the relay 1. In particular, using the principles of electromagnetic induction (whereby an electro-motive force or ENT, is created from a changing magnetic field around an electric conductor and, conversely, a current flow is created by moving an electric conductor through a static magnetic field), information about the current in the coils and the movement of the armature can be determined. This determination of the state of the relay is discussed below in more detail with respect to Figure 5 (Figures 5a and 5b).

In accordance with Figure 5a, the relay 1 comprises the drive unit 2 and means for applying a current I through the coil 21. In this example, the means 50 comprises a capacitor which is configured to discharge through the coil 21. The relay 1 also comprises means 52 for detecting/measuring a voltage V across the coil. The means 52 can comprise a voltage probe or any suitable voltage measurement device or sensor. In this example, the means 52 are configured to detect the voltage across coil 21. However, in other examples a second coil (not shown) may be arranged/disposed around coil 21, and the means 52 are configured to detect the voltage across this so additional coil instead of, or as well as, the voltage across coil 21.

The measured voltage is provided to means 54 for determining a status 56 of the electromagnetic relay 1 based on the measured voltage, V. In particular, the means 54 can be configured to determine the status based on one or more characteristics of the measured voltage. The one or more characteristics can include one or more of: an amplitude of a detected peak in the measured voltage, a duration of the detected peak, a polarity of the measured voltage, a gradient of a voltage-time curve for the measured voltage, and/or a dip in the voltage-time curve. In other examples, the means for determining a status can comprise means for detecting a peak in the measured voltage means for determining, based on one or more characteristics of the detected peak, the status of the electromagnetic relay.

The status of the electromagnetic relay can indicate a fault condition and/or a health of the electromagnetic drive unit 2. The fault condition can be indicative of rotation of the armature 3 without application of the current through the coil 21 (i.e. without discharge of the capacitor or activation of the other means 50). Such a movement of the armature can be due to, for example, vibrations or manual opening/closing of the relay, as well as or instead of degradation of the magnetics holding the armature in place due to time and/or environmental factors. The fault condition can be indicative of application of the current through the coil 21 (i.e. discharge of the capacitor or activation of other means 50) without rotation of the armature 3. This lack of movement of the armature can be due to, for example, failure or a fault in the electromagnetic drive unit or magnetic sub-system. By enabling to detect a status of the relay using existing coils of the relay, and without the need for an external power supply, a more robust relay may be provided.

The means 54 can he included as part of the relay 1, as shown in Figure 5a, or canbe remote from the relay as part of a system 60 comprising the relay 1 and a computing device 58, as shown in Figure 5b. Means 54 can be a PCB or any other suitable processing means. The status 56 can be output to an operator of the relay and/or at a device comprising or incorporating the relay as a notification or alert, for example. This can inform an operator or user that a fault condition is occurring, or that a health of the relay may need to be investigated. Safety of the relay may therefore be improved.

In a first example, described with reference to Figures 6a, 6b, detection of movement of the armature 3 without a corresponding discharge of the capacitor 50 or application of a current by means 50 through the coil 21 is now described. In this first example, the voltage is measured across the existing coil 21, which is wound around the yoke 4. The existing relay components can therefore be used to monitor unintended movement of the armature 3.

Example experimental data is shown in Figures 6a, 6b (voltage against time).

the armature is opened manually (for experimental purposes), e,g, by turning a contact bridge mechanically, without application of any current to coil 21, a voltage signal is obtained due to the change in the magnetic field from the rotation of the -12 -armature. The voltage signal arises from the changing flux paths as the armature moves (e.g. a moving/varying magnetic field). When the contacts are opened, a voltage peak of 4.32 V was observed, with a peak duration of 1.02 ms (Figure 6a). When the contacts are dosed, a voltage peak of 3.04 V was observed, with a peak duration of 1.35 ms (Figure 6b). The differences in the orientation of the peak are due to the direction of rotation of the armature (i.e. the voltage has a different polarity depending on whether the contacts are being opened or dosed). Thus, the characteristics of the measured voltage being considered include the peak amplitude of the measured voltage and the duration of the detected peak.

It is thus shown that movement of the armature can be detected even in the absence of an application of current by means 50 through the cod 21 by the drive unit 2. The coil can thus be used to detect unintended opening or closing of the relay, for example due to degradation of the magnetic system owing to time/environmental factors, or vibrations from the environment, for example. The detected voltage can also be used to monitor the switching status of the relay 1, by detecting whether contacts are opening or dosing. By using the existing coil, a more robust relay 1 can be provided since no external power supply is needed.

in a second example, described with reference to Figures 7a,7b, detection of movement of the armature 3 without a corresponding discharge of the capacitor 50 or application of a current by means 50 through the coil 21 is now described. In this second example, the voltage is measured across an additional coil, which is disposed around the existing coil 21 (e.q, wound on top of, and concentric with, coil 21). In particular, it has been found that each cycle generates a peak of about 7 V in the additional coil (disposed around coil 21) when the capacitor discharges, with a peak duration of 180 microseconds (us). The additional coil can therefore be used for monitoring the state of the armature as well as, or instead of, coil 21.

Example experimental data is shown in Figures 7a, 7b (voltage against time). When the armature is opened manually (for experimental purposes), e.g. by turning a contact bridge mechanically, without application of any current to coil 21, a voltage signal is obtained in the additional coil due to the change in the magnetic field from the rotation of the armature. The voltage signal arises from the changing flux paths as the armature moves (e.g. a moving/varying magnetic field). When the contacts are opened, a voltage peak of 1.14 V was observed, with a peak duration of 0.96 ms (Figure 7a). When the contacts are closed, a voltage peak of 780 my was observed, with a peak duration of 1.35 ms (Figure 7b). The differences in the orientation of the peak are due to the direction of rotation of the armature and the orientation of the coil (i.e. the voltage has a different polarity depending on whether the contacts are being opened or dosed and/or the clockwise or anti-clockwise direction of the coil winding). Thus, the characteristics of the measured voltage being considered include the peak amplitude of the measured voltage and the duration of the detected peak, It is thus shown that movement of the armature can be detected usinci an additional coil, even in the absence of an application of current by means 50 through the coil 21 by the drive unit 2. The magnitude of the measured voltage varies, depending on io which coil is used. This additional coil can thus be used to detect unintended opening or closing of the relay, for example due to system degradation arising from changes in magnetic strength due to time/environmental factors and/or vibrations from the environment. The detected voltage can also be used to monitor the switching status of the relay 1, by detecting whether contacts are opening or closing. By using an additional coil and measuring voltage in this way, a more robust relay 1 can be provided since no external power supply is needed.

In a third example, described with reference to Figures Sa,8b, detection of discharge of the capacitor 50 or application of a current by means 50 through the coil 21 without corresponding rotation of the armature 3 is now described. In this third example, the voltage is measured across coil 21, but an additional coil could be used as well or instead of coil 21, as discussed above. In particular, it has been found that a voltage peak with a dip in the signal is measured when the armature moves (voltage signal is due to both electromagnetic field generated due to capacitor discharge and the change in magnetic field established by the permanent magnets 23, 24 due to the armature movement). However, a voltage peak is measured without such a dip when there is no armature movement. (voltage signal is due only to the magnetic field generated by capacitor discharge through the coil). The peak is higher when there is armature movement (and hence contact opening/closing). In a specific example, the peak with armature movement was measured at 43.6 V, and the peak without armature movement was measured at 38.4 V when the two coils were combined together, i.e. when the coil 21 and additional coil were connected in series. Similar voltage signal patterns (but smaller magnitudes, in the range of 20 V) were obtained for both the coil 21 and the additional coil when the voltages were measured across these coils separately (not shown here).

Example experimental data for a signal coil is shown in Figures 8a, 8b (voltage against time). When there is armature movement, as shown in Figure Sa, the voltage-time -14 -curve measured across the coil exhibits a peak followed by a dip (as highlighted by the dashed circles in Figures 8a). Example peaks of 2.2 V and 2.24 V were measured in arrangements with armature movement. When there is no armature movement; as shown in Figure 8b, there is no such dip in the measured voltage-time curve. Example peaks of 1.96 V and 1.92 V were measured in the absence of armature movement. Thus, the characteristics of the measured voltage being considered include the peak amplitude of the measured voltage and whether there is a dip in the voltage-time curve after the detected peak. The differences in the orientation of the peak are due to the direction of rotation of the armature and/or the orientation of the o coil (i.e. the voltage has a different polarity depending on whether the contacts are being opened or closed). In other words, the voltage level can be positive or negative depending on the arrangement of the relay.

It is thus shown that the application of current movement but the failure of the armature to move can he. detected using coil 21 or an additional coil. By measuring the application of current, faults in the relay 1 can be isolated to e.g. the magnetic sub-system. In other examples, comparing the measured voltage to known voltages for correct discharge of the capacitor can allow to identify faults with the capacitor operation, for example (e.g. not fully discharging, or discharging too slowly to drive the armature). In this way, health of the capacitor itself, or the drive unit 2 more generally, can be ascertained and/or monitored over time. For example, voltage signals can be collected continuously or at periodic intervals to determine signatures of an individual relay, and changes in the health of the relay determined based on variations of the signature over time.

The determination of the status can he performed in any suitable manner. for example, one or more algorithms, rules, models; lookup tables, transforms and/or processing functions can be applied to the measured voltage to assess the characteristics described herein and determine the status. Moreover; any suitable calibration steps can be performed at the relay to facilitate implementation of the approach described herein.

he determining can be performed at or by the relay itself, or at/by a computing device which is associated with the relay (i.e. which receives the measured voltage from the relay). Although not shown here, any suitable means for outputting the status (or an indication of the status) can also be provided, such that an alert, notification or alarm can be output based on the determined status. For example, an alert may be output to an operator of the relay and/or at a device comprising or incorporating the relay. The status may be output as an audible output (for example at a speaker), a haptic or tactile output, and/or a visual output (for example at a display).

Monitoring and analysing one or more characteristics of the voltage measured across one or more coils of the relay, as discussed above, can allow to determine a status or fault or relay 1, as well as to confirm a successful relay operation. Therefore, the voltage can be used to determine the status of the relay (e.g. open, closed) based on the principles described herein, in addition to determining one or more fault conditions and/or a health of the electromagnetic relay 1. A more robust relay may therefore be provided.

Claims

Cairns 1. An electromagnetic relay (1), comprising: an electromagnetic drive unit (2), comprising: a rotatable armature (3) having a first magnetic contact region (5); a yoke having a second magnetic contact region (6); the first magnetic contact region being in physical contact with the second magnetic contact region in a first state of the relay; and at least one coil (21) wound at least in part around a portion of the yoke a fixed electrical conductor (7); a rotatable electrical conductor (8) coupled J the rotatable armature, the rotatable electrical conductor configured to be in electrical contact with the fixed electrical conductor in the first state of the relay, wherein the electromagnetic drive unit is configured to apply a current through the at least one coil to cause the armature to rotate to a second state of the relay, wherein in the second state of the relay the rotatable electrical conductor is not in electrical contact with the fixed electrical conductor and the first maonetic contact region is not in physical contact with the second magnetic contact region; means for measuring a voltage across the at least one coil; and means for determining, based on one or more characteristics of the measured voltage, a status of the electromagnetic relay.
2. The electromagnetic relay of claim 1, wherein the one or more characteristics include one or more of: an amplitude of a detected peak in the measured voltage, a duration of the detected peak, a polarity of the measured voltage; a gradient of a voltage-time curve for the measured voltage, and/or a dip in the voltage-time curve.
3. The electromagnetic relay of claim 1. or claim 2, wherein the status of the electromagnetic relay indicates a fault condition or a health of the electromagnetic o drive unit.
4. The electromagnetic relay of claim 3, wherein the fault condition is indicative of: rotation of the armature without application of the current through the at least as one coil; or application of the current through the at least one coil wit ation of the armature; or hoot -17 -application of the current through the at least one coil with rotation of the armature being below a threshold speed.
5. The electromagnetic relay of any preceding claim, wherein the electromagnetic drive unit comprises a capacitor and is configured to cause the capacitor to discharge to apply the current through the at least one coil.
6. The electromagnetic relay of claim 5, wherein the fault condition is indicative of rotation of the armature without discharge of the capacitor, or wherein the fault to condition is indicative of discharge of the capacitor without rotation of the armature.
The electromagnetic relay of any preceding claim, wherein the at least one coil comprises a first coil, and wherein the electromagnetic drive unit is configured to app he current through the first coil to cause the armature to rotate.
8. The electromagnetic relay of any of claims 1 to 6, wherein the at least one coil comprises a first coil and a second coil, the first coil disposed around the second coil, and wherein the electromagnetic drive unit is configured to apply the current through the second coil to cause the armature to rotate.a.
The electromagnetic relay of claim 7 or claim 8, wherein the means for measuring are configured to measure the voltage across the first coil.13.
The electromagnetic relay of any preceding claim, wherein: the rotatabie armature comprises a third magnetic contact region (16) opposite the first magnetic contact region, and the yoke comprises a fourth magnetic contact region (17), the third magnetic contact region being in physical contact with the fourth magnetic contact region in the first state of the relay, and the at least one coil Further comprises an additional coil (22) wound at least in part around an additional portion of the yoke, the means for measuring a voltage across the at least one coil comprising means for measuring the voltage across the additional coil.-18 -
11. The electromagnetic relay of any preceding claim, further comprising one or more biasing members (19, 20) configured to bias the rotatable electrical conductor towards the first state of the relay.
12. The electromagnetic relay of any preceding claim, wherein the means for measuring a voltage across the at least one coil comprise a voltage probe, and the wherein the means for determining a status of the electromagnetic relay comprise a PCB.
13. A hybrid circuit breaker comprising a semiconductor switching unit and a bypass relay arranged in parallel to the semiconductor switching unit, wherein the bypass relay comprises the electromagnetic relay of any preceding claim.
14. A system, comprising: an electromagnetic relay (1), comprising: an electromagnetic drive unit (2), comprising: a rotatable armature (3) having a first magnetic contact region a yoke (4) having a second magnetic contact region (6); the first magnetic contact region being in physical contact with the second magnetic contact region in a first state of the relay; and at least one coil (21) wound at least in part around a portion of the yoke; a fixed electrical conductor (7); a rotatable electrical conductor (8) coupled to the rotatable armature, the rotatable electrical conductor configured to be in electrical contact with the fixed electrical conductor in the first state of the relay, wherein the electromagnetic drive unit is configured to apply a current through the at least one coil to cause the armature to rotate to a second state of the relay, wherein in the second state of the relay the rotatable electrical conductor is not in electrical contact with the fixed electrical conductor and the first magnetic contact region is not in physical contact with the second magnetic contact region; and means for measuring a voltage across the at least one coil; and a computing device, comprising means for determining, based on the measured voltage, a status of the electromagnetic relay.
15. The system of claim 14, wherein the means for determining the statics of -he electromagnetic relay comprises: means for detecting a peak in the measured voltage; and means for determining, based on one or more characteristics of the detected peak, the status of the electromagnetic relay.