System and method for monitoring remaining useful life of a capacitor in an uninterruptable power supply

Abstract

An apparatus and method of monitoring remaining useful life of a capacitor in an UPS supply is provided. Telemetry data of the UPS is acquired (301) that comprises at least a load percentage, an internal ambient temperature and data relating to a mode of operation of the uninterruptible power supply. A capacitor life adjustment factor is determined (302) based upon the telemetry data and design data of the capacitor. The capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor. A remaining useful life value of the capacitor is determined (303) based upon the capacitor life adjustment factor and a previous remaining useful life value. The remaining useful life value is compared (304) to a threshold. An alert is output as a function of the remaining useful life value, for example when the remaining useful life value is less than the threshold.

Description

[0001] SYSTEM AND METHOD FOR MONITORING REMAINING USEFUL LIFE OF A CAPACITOR IN AN UNINTERRUPTABLE POWER SUPPLY

[0002] Field

[0003] Aspects of the present disclosure relate to uninterruptable power supplies and monitoring the remaining useful life of capacitors in uninterruptable power supplies.

[0004] Background

[0005] Capacitors, and in particular aluminium electrolytic capacitors, are used in uninterruptable power sources (UPSs) to smooth out fluctuations in voltage; this is known as supply voltage filtering. As with other electrical components, capacitors degrade over time and reach the end of their useful life.

[0006] When a capacitor reaches the end of its useful life, it might not be possible to see any visible effects indicative of this. However, other capacitors in the UPS will have to take over the workload, which in turn shortens their useful lives. Moreover, when this reduced capacitance reaches a certain level, the UPS may not function properly.

[0007] Existing methods for identifying when a capacitor has reached the end of its useful life, which include visual inspection and / or capacitance / equivalent series resistance measurement suffer from drawbacks including: (1) low accuracy as some end of useful life modes will not manifest in a physical deformation, (2) low accuracy as not all capacitors are in a line of sight of an operator and are therefore difficult to inspect visually, (3) the need to take a UPS offline to measure capacitance of equivalent series resistance, during which time downstream loads are not protected, (4) higher costs of health assessment as offline testing needs sophisticated instrumentation and trained operators to perform the offline testing, (5) a lack of prior intimation regarding the impending end of life, and (6) additional costs of sensors and processors to measure and process high frequency signals such as voltage and current.

[0008] Aspects herein address the afore mentioned challenges, amongst others. Summary

[0009] A method of monitoring remaining useful life of a capacitor in an uninterruptable power supply is disclosed, comprising:

[0010] - obtaining design data of the capacitor,

[0011] - obtaining telemetry data from the uninterruptable power supply,

[0012] - determining a capacitor life adjustment factor based upon the design data of the capacitor and the telemetry data of the uninterruptable power supply, wherein the capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor;

[0013] - determining a remaining useful life value of the capacitor based upon the capacitor life adjustment factor and a previous remaining useful life value;

[0014] - outputting an alert as a function of the determined remaining useful life value.

[0015] In an embodiment, the disclosed method further comprises comparing the remaining useful life value to a predetermined threshold value; and outputting the alert when the remaining useful life value is less than the predetermined threshold value.

[0016] For example, the predetermined threshold value is a first predetermined threshold value, and the alert is a first alert, the method further comprising comparing the remaining useful life value to a second predetermined threshold value and outputting a second alert when the remaining useful life value is less than the second predetermined threshold value, wherein the second predetermined threshold value is less than the first predetermined threshold value.

[0017] In an embodiment of the disclosed method, the capacitor is an aluminium electrolytic capacitor.

[0018] In an embodiment of the disclosed method, the capacitor life adjustment factor is representative of the remaining useful life under the current operating conditions of the capacitor as related to the rated life at the rated operating conditions of the capacitor.

[0019] In an embodiment of the disclosed method, the determination of the temperature factor comprises: deriving an ambient temperature around the capacitor from an ambient temperature of the uninterruptable power supply by adding a temperature rise value, and determining the temperature factor as a function of a comparison of the derived ambient temperature around the capacitor with a value of rated temperature of the capacitor, the temperature rise value being a constant value included in the design data or being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, the value of rated temperature being included in the capacitor design data, and the value of the ambient temperature of the uninterruptable power supply being included in the telemetry data.

[0020] In an embodiment of the disclosed method, the determination of the voltage factor comprises calculating the ratio of a rated voltage of the capacitor over a voltage applied across the capacitor and raising the ratio to a constant exponent, the value of the voltage applied across the capacitor being either a constant voltage value included in the capacitor design data or a measurement included in the telemetry data of the uninterruptible power supply, and the rated voltage and the constant exponent being included in the capacitor design data.

[0021] In an embodiment of the disclosed method, the determination of the ripple current factor comprises: determining a parameter representative of the difference between a surface temperature of an outer casing of the capacitor and an ambient temperature around the capacitor, based on a value of the ripple current flowing through the capacitor, a rated ripple current and a core temperature rise of the capacitor at the rated ripple current, determining the ripple current factor as a function of a comparison of said parameter with the core temperature rise of the capacitor at the rated ripple current, the value of the ripple current flowing through the capacitor being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, and the rated ripple current and the core temperature rise of the capacitor at the rated ripple current being included in the capacitor design data.

[0022] For example, the load percentage on the uninterruptable power supply is representative of the ratio of the power being used by a load connected to the uninterruptable power supply to the maximum power capacity that the uninterruptable power supply can handle. In addition, an apparatus is disclosed which is configured to monitor remaining useful life of a capacitor in an uninterruptable power supply. The disclosed apparatus comprises means for: obtaining design data of the capacitor, acquiring telemetry data of the uninterruptable power supply, determining a capacitor life adjustment factor based upon the design data of the capacitor and the telemetry data of the uninterruptable power supply, wherein the capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor; determining a remaining useful life value of the capacitor based upon the capacitor life adjustment factor and a previous remaining useful life value; outputting an alert as a function of the determined remaining useful life value.

[0023] In an embodiment, the disclosed apparatus further comprises means for comparing the remaining useful life value to a predetermined threshold value; and outputting the alert when the remaining useful life value is less than the predetermined threshold value.

[0024] For example, the predetermined threshold value is a first predetermined threshold value, and the alert is a first alert, the method further comprising comparing the remaining useful life value to a second predetermined threshold value and outputting a second alert when the remaining useful life value is less than the second predetermined threshold value, wherein the second predetermined threshold value is less than the first predetermined threshold value.

[0025] In an embodiment of the disclosed apparatus, the determination of the temperature factor comprises: deriving an ambient temperature around the capacitor from an ambient temperature of the uninterruptable power supply by adding a temperature rise value, and determining the temperature factor as a function of a comparison of the derived ambient temperature around the capacitor with a value of rated temperature of the capacitor, the temperature rise value being either a constant value included in the design data or being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, the value of rated temperature being included in the capacitor design data, and the value of the ambient temperature of the uninterruptable power supply being included in the telemetry data.

[0026] In an embodiment of the disclosed apparatus, the determination of the voltage factor comprises calculating the ratio of a rated voltage of the capacitor over a voltage applied across the capacitor and raising the ratio to a constant exponent, the value of the voltage applied across the capacitor being either a constant voltage value included in the capacitor design data or a measurement included in the telemetry data of the uninterruptible power supply, and the rated voltage and the constant exponent being included in the capacitor design data.

[0027] In an embodiment of the disclosed apparatus, the determination of the ripple current factor comprises: determining a parameter representative of the difference between a surface temperature of an outer casing of the capacitor and an ambient temperature around the capacitor, based on a value of the ripple current flowing through the capacitor, a rated ripple current and a core temperature rise of the capacitor at the rated ripple current, determining the ripple current factor as a function of a comparison of said parameter with the core temperature rise of the capacitor at the rated ripple current, the value of the ripple current flowing through the capacitor being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, and the rated ripple current and the core temperature rise of the capacitor at the rated ripple current being included in the capacitor design data.

[0028] For example, computer program instructions or software code which executes on a programmed processing apparatus implements the above-mentioned functions.

[0029] Also, a non-transitory computer-readable medium is disclosed which stores instructions thereon which when executed by one or more processors cause the one or more processors to perform the steps of any embodiment of the method disclosed herein.

[0030] The disclosed method and apparatus overcome the above-mentioned limitations of known alternatives. They project when the capacitor in an uninterruptable power supply (UPS) will reach its end of life based on usage history, by using real time data (UPS operating state, load percentage, ambient temperature around the UPS) and life deduction models (e.g. based on Arrhenius law I Inverse Power law). Advantageously they combine using a thermal and a voltage life deduction model. Advantageously, the thermal stress is inferred using an estimation of the ripple current and an estimation of the case temperature which can be obtained from a load percentage of the uninterruptable power supply. Advantageously the capacitor usage is determined from operating state of the UPS (rule-based determination). This approach reduces the overall costs as no additional sensor is required.

[0031] Brief Description of Drawings

[0032] Examples of the disclosure are now described with reference to the drawings, in which:

[0033] Figure 1 is a block diagram of an apparatus configured to determine and monitor the remaining useful life of a capacitor in an uninterruptable power supply;

[0034] Figure 2 is a flow chart of a process for determining and monitoring the remaining useful life of a capacitor in a UPS;

[0035] Figure 3 is a flow chart of a method for monitoring the remaining useful life of a capacitor in a UPS based upon the process of Figure 2; and

[0036] Figure 4 is a high-level block diagram of an apparatus suitable for implementing various aspects of the disclosure.

[0037] Detailed Description

[0038] Figure 1 shows a block diagram of an apparatus 100 configured to determine and monitor the remaining useful life (referred to as RUL) of a capacitor in an uninterruptable power supply (UPS) 10. In an example, the capacitor can be an aluminium electrolytic capacitor. In some examples, the apparatus 100 can be a computer or the like.

[0039] The apparatus 100 includes an interface module 102 through which the apparatus acquires telemetry data from the UPS. The interface 102 can be used to receive the telemetry data for example as a wired or wireless interface configured to receive the telemetry data through a network or by direct connection to the UPS 10. The telemetry data comprises measurement data relating to a capacitor in the UPS for which the remaining useful life is to be determined.

[0040] The telemetry data is processed by a processing module 104 configured to determine the remaining useful life of the capacitor in the UPS 10. The processing module 104 can be, for example, one or more processors configured to execute instructions stored in computer-readable storage accessible by said one or more processors, wherein said instructions perform steps for determining the remaining useful life of the capacitor in the UPS 10, as will be discussed.

[0041] An output module 106, that can be an output means, can be controlled to output an alert when the remaining useful life of the capacitor drops below a certain point. For example, the output module 106 could be a speaker or the like, configured to output an audible notification. Alternatively, the output module 106 could be a visual indicator such as a display screen or one or more light, configured to output a visual notification. In some examples, the output module 106 could be configured to output the alert to a separate device.

[0042] The functionality of the modules of Figure 1 are discussed in more detail by reference to Figure 2 and Figure 3.

[0043] Factors including applied voltage, ambient temperature and ripple current can influence the life of a capacitor. The methodology of the present disclosure utilises these factors in determining the remaining useful life of a capacitor in a UPS.

[0044] The apparatus acquires telemetry data from the UPS. The telemetry data includes a load percentage LP of the UPS, an ambient temperature around the UPS noted TA, and depending on the embodiment, a voltage across the capacitorappiied. These parameters are then used in determining the remaining useful life RUL of the capacitor.

[0045] A capacitor life adjustment factor is determined. The capacitor life adjustment factor includes a voltage factor, a temperature factor, and a ripple current factor, such that: wherein, c is the capacitor life adjustment factor, Kvoitage(i) is the voltage factor, Ktemperature(i) is the temperature factor, KriPPie(i) is the ripple current factor for time interval i (i being an integer).

[0046] The capacitor life adjustment factor for time interval i can be understood as: such that — is a factor relating the remaining useful life under the operating conditions io for ithtime interval (L) to the rated life at the rated operating conditions of the capacitor

[0047] (Lo). Lo is also referred to as design life. It is an estimate of the operational lifespan at rated temperature, rated voltage and rated ripple current. It is part of the specification data.

[0048] In other words, the capacitor life adjustment factor aLallows time (e.g., hours) accumulated under any set i of operating conditions to be converted to equivalent time (e.g., hours) at the rated conditions.

[0049] Then, the remaining useful life for time interval i (RUL) can determined in an iterative manner as: wherein RULM is the remaining useful life determined for the i-1thinterval, and Ui is the calendar time (e.g., number of hours) between the i-1thmeasurements and the ithmeasurements.

[0050] The capacitor life adjustment factor aLcan be considered as an acceleration factor associated with the rate at which the decrease in remaining useful life is accelerating.

[0051] As a function of the value determined for the remaining useful life RUL, an alert can be triggered. For example, when the remaining useful life RUL drops below a threshold, an alert can be triggered. In this way, an operator can be made aware that the capacitor should be replaced or will soon need to be replaced.

[0052] In cases where there is no i-1thinterval because the calculation of the remaining useful life is being determined for the first time (i.e., i = 1 , or the first iteration), RUL0can be set as equal to the design life at the rated operating conditions of the capacitor (Lo).

[0053] The voltage factor (Kvoitage) can be determined as a function of the rated voltage (rated) of the capacitor, and the voltage applied across the capacitor in operation ( aPPiied): 1.25

[0054] When -^2^- > 1.25, Kvoitage= 1 applied

[0055] The factor M is provided by the manufacturer (it is determined by the manufacturer so that the observed data match the theorical capacitor model of the manufacturer). It is part of the capacitor design data. In an embodiment, the voltage applied across the capacitorappiied is set to a constant value for a given type of capacitor. In this case the constant value ofappiied is stored in the cloud as part of the capacitor design data. In another embodiment, the voltageappiied is measured and is part of the telemetry data of the uninterruptible power supply.

[0056] For example, the factors Knppie and Ktemperature are determined using a general form of the Arrhenius relationship. The below equations which are proposed to determine the factors Knppie and Ktemperature reflect that an increase of 10°C will double the rate of degradation.

[0057] The temperature factor (Ktemperature) can be determined as a function of the rated temperature To of the capacitor and the local ambient temperature around the capacitor Tx : where :

[0058] • To is the rated temperature of the capacitor

[0059] • Tx is the local ambient temperature around the capacitor and is determined as TX=TA+TRwhere TRis the temperature rise

[0060] • TA is the ambient temperature of the UPS (it is measured and provided by the UPS as part of the telemetry data).

[0061] In an embodiment, the temperature rise TRis a constant value which is included in the design data of the capacitor. In another embodiment, the temperature rise TRis inferred by interpolating the value of TRfrom a table of UPS loads and temperature rises. The table can be obtained from lab measurements. It is stored in the cloud and is accessible by the apparatus.

[0062] The ripple current factor (Knppie) can be determined as follows:

[0063] ATQ-AT ^ripple 10 where:

[0064] • AT0is the core temperature rise of the capacitor at rated ripple current Io. It is a constant value provided by the manufacturer. • AT is representative of the difference between the surface temperature Tsof the outer casing of the capacitor and the local ambient temperature Tx around the capacitor.

[0065] For example, AT can be determined using the following equation : where:

[0066] • Io is the rated ripple current

[0067] • Ixis the ripple current flowing through the capacitor.

[0068] The value of Ixis inferred by interpolating the value of Ixfrom a table of UPS loads and ripple currents. The table can be obtained from lab measurements in the product. It is stored in the cloud and it can be accessed by the apparatus. Advantageously, the interpolated ripple current is corrected for frequency.

[0069] The above equations for the determination of the voltage factor Kvoitage, the temperature factor Ktemperature, and the ripple factor Krippie are given by way of examples. Variations or alternative equations can be used.

[0070] Using these three factors, combined thermal and voltage life deduction models are accounted for when determining the remaining useful life, thereby improving the accuracy of the determination.

[0071] The UPS can comprise a plurality of types of capacitors and the UPS can operate in different modes, for example: dual conversion / online mode, battery mode, by-pass mode, etc. A given type of UPS capacitors might not be in use for all operating modes of the UPS. For each type of capacitor, a table of operation modes or states is established which indicates for each mode whether the type of capacitor is involved in the operations. For example, the tables of operating modes are stored in the cloud. They are accessible by the apparatus.

[0072] Figure 2 shows, in more detail, a flow chart of a process for determining and monitoring the remaining useful life of a capacitor in a UPS as outlined above.

[0073] The process starts at step 201 and proceeds to step 202 where capacitor design data of the capacitor being monitored is read. For example, capacitor design data are stored in cloud and retrieved by the apparatus 100 from the cloud. For example, the capacitor design data can include amongst other: the rated voltage, the rated temperature, the rated ripple current (at rated temperature and voltage), the design life Loof the capacitor, for example in hours, the capacitance, and the above-mentioned constant values: the factor M and the core temperature rise AT0of the capacitor at rated ripple current. When the temperature rise TRand / or the voltageappiied across the capacitor are assumed to be constant, their value is also part of the retrieved design data.

[0074] At step 203, the apparatus 100 accesses a previous value of the remaining useful life (i.e., RULM) of the capacitor from processing history stored in storage accessible by the apparatus 100. This previous value can be the value of the remaining useful life determined in an immediately preceding loop of the process of Figure 2. In cases where there is no processing history (i.e., no immediately preceding loop of the process), for example because this it is the first time the process has been run for the capacitor, the apparatus can set the previous value of the remaining useful life as the design life Loof the capacitor.

[0075] In an embodiment, at step 204, the UPS operating modes for which the capacitor is in use are retrieved from the associated table of operating mode in the cloud.

[0076] At step 205, the apparatus 100 obtains telemetry data of the UPS for the ithinterval. The telemetry data can be sent by the UPS to the apparatus. Alternatively, the apparatus can access the UPS and read the telemetry data. In other words, the apparatus acquires the telemetry data; this can be via the interface module 102 of the apparatus 100.

[0077] The telemetry data comprises at least a load percentage on the UPS (referenced LP in Figure 2) which is the ratio of the actual power being used by the load connected to the UPS to the maximum power capacity that the UPS can handle, the internal ambient temperature TA around the UPS and the current operating mode of the UPS (referenced OP in figure 2). When the voltage across the capacitorappiied is not assumed to be constant, it is also part of the telemetry data.

[0078] The data OP relating to the mode of operation of the UPS can comprise the mode of operation of the UPS itself, or data allowing to derive the mode of operation of the UPS.

[0079] At step 206, the apparatus 100 pre-processes the telemetry data to remove junk data (e.g. data associated with a negative load percentage are assumed to be junk) and converting the data into the appropriate units (e.g. converting temperature data from Kelvin to Degree Celsius). At step 207, the apparatus 100 calculates the capacitor operating time Ui.

[0080] The capacitor operating time Ui can be the time (for example in hours) for which the capacitor has been under the current operating conditions. This can be considered as the time since the previous remaining useful life determination RULM (i.e., the preceding loop of the process of Figure 2).

[0081] When the operating mode of the UPS obtained at step 205 is not part of the modes in which the capacitor is in use (retrieved at step 204), no time is accumulated.

[0082] At step 209, the apparatus 100 can determine the voltage factor Kvoitage(i) used in the determination of the remaining useful life of the capacitor RUL. The voltage factor can be determined as described above, using the rated voltagerated of the capacitor and the voltage applied across the capacitor Vappiied(i) (which can be assumed to be constant or can be part of the telemetry data).

[0083] At step 210, the ripple current lxof the capacitor can be determined using the load percentage LP included in the telemetry data. The ripple current can be determined by using the predetermined table of load percentage values and corresponding ripple current values.

[0084] At step 21 1 , the apparatus 100 can determine the ripple current factor Krippie(i) used in the determination of the remaining useful life of the capacitor RUL. The ripple current factor can be determined as described above based on the ripple current lx.

[0085] At step 212, when applicable, the apparatus 100 can convert the ambient temperature TA of the UPS to degrees centigrade.

[0086] At step 213, the apparatus 100 can determine the temperature factor Ktemperature(i) from the ambient temperature TAas described above. The temperature rise TRis either a constant value retrieved as part of the design data or it can be interpolated from the predetermined table of load percentage values and corresponding temperature rise values.

[0087] At step 214, the apparatus 100 can determine the capacitor life adjustment factor aLas described above: At step 215, the apparatus can determine the remaining useful life value RUL of the capacitor based upon the capacitor life adjustment factor aLand a previous remaining useful life value RULM , as described above:

[0088] The previous remaining useful life value (RULM) can be accessed from storage associated with the apparatus 100.

[0089] At step 216, a regression can be fitted between the days in service of the capacitor (i.e., Ui) and the determined value of the remaining useful life (RUL) of the capacitor. This regression can use a straight line or linear projection to predict the end of the useful life of the capacitor. This can be envisaged as the days in service (i) as a function of remaining useful life (RUL). For example, the fit could be between the maximum expected useful life RUL0of the capacitor (i.e., the expected life for a new capacitor based upon the rated operating conditions of the capacitor), and the value of the remaining useful life determined for time interval i. In another example, the fit could be based upon each data point from RUL0to RUL such that the fit is refined each time the process is executed in a loop type manner.

[0090] At step 217, the regression can then be extrapolated to determine the number of days in service at which the remaining useful life will reach zero.

[0091] At step 218, it is determined whether the number of days until the remaining useful life will reach zero is less than a first predetermined threshold number of days. For example, this could be 180 days. When the remaining useful life will reach zero is less than the first predetermined threshold number of days, a first alert is output by the output module to inform the operator that the capacitor is approaching the end of its useful life.

[0092] At step 219, it is determined whether the number of days until the remaining useful life will reach zero is less than a second predetermined threshold number of days. For example, this could be 30 days. When the remaining useful life will reach zero is less than the second predetermined threshold number of days, a second alert is output by the output module to inform the operator that the capacitor is approaching the end of its useful life.

[0093] The second threshold number of days can be lower than the first threshold number of days. In this way, the operator is given a first warning, and then a second warning nearer to the end of the useful life of the capacitor. In this way, the operator can be prepared to replace the capacitor in good time to avoid failure of the UPS.

[0094] Whilst two thresholds are described at steps 217 and 218, the skilled person will understand that any suitable number of thresholds can be used, where the number of thresholds can be integer values greater than or equal to one.

[0095] At step 220, the process returns to step 201 with i=i+1 .

[0096] The process of Figure 2 can be operated as an iterative loop that executes at predetermined intervals, for example every day, to constantly monitor the remaining useful life of the capacitor in a real-time manner.

[0097] Whilst the foregoing disclosure refers to the remaining useful life as a function of days, it could equally be determined as any suitable unit of time, such as minutes or hours. In some examples, a percentage of remaining useful life as a function of maximum expected useful life may be used. In such examples, the threshold values (steps 218, 219) can be percentages, such as 35% of remaining useful life (first threshold), and 20% of remaining useful life (second threshold).

[0098] Steps 202 to 217 can be performed by the processing module 104 of the apparatus 100. Steps 218 and 219 can be performed by the output module 106 of the apparatus 100.

[0099] Figure 3 shows a flow chart of a method for monitoring the remaining useful life of a capacitor in a UPS based upon the process of Figure 2.

[0100] At step 301 , telemetry data of the UPS is acquired by the apparatus, for example using the interface module 102. The telemetry data comprises a load percentage of the capacitor, an internal ambient temperature of the capacitor, a voltage across the capacitor, and data of one or more events relating to a mode of operation of the uninterruptible power supply.

[0101] At step 302, the capacitor life adjustment factor is determined based upon the telemetry data, wherein the capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor. Step 302 can be performed by the remaining useful life determination module 104, as described with reference to Figure 1 .

[0102] At step 303, the remaining useful life value of the capacitor is determined based upon the capacitor life adjustment factor and a previous remaining useful life value. Step 303 can be performed by the remaining useful life determination module 104, as described with reference to Figure 1.

[0103] At step 304, the remaining useful life value is compared to a predetermined threshold value. Step 304 can be performed by the remaining useful life determination module 104, as described with reference to Figure 1.

[0104] At step 305, an alert is output when the remaining useful life value is less than the predetermined threshold value. Step 305 can be performed by the output means 106, as described with reference to Figure 1 .

[0105] Figure 4 depicts a high-level block diagram of an apparatus 400 suitable for implementing various aspects of the disclosure. Although illustrated in a single block, in other embodiments the apparatus 400 may also be implemented using parallel and distributed architectures. Thus, for example, various steps such as those illustrated in the methods described above by reference to Figures 2 and 3 may be executed using apparatus 400 sequentially, in parallel, or in a different order based on particular implementations. The abnormal power consumption detection apparatus can be implemented in the form of apparatus 400.

[0106] According to an exemplary embodiment, depicted in Figure 4, apparatus 400 comprises a printed circuit board 401 on which a communication bus 402 connects a processor 403 (e.g., a central processing unit "CPU"), a random access memory 404, a storage medium 411 , possibly an interface 405 for connecting a display 406, a series of connectors 407 for connecting user interface devices or modules such as a mouse or trackpad 408 and a keyboard 404, a wireless network interface 410 and / or a wired network interface 412. Depending on the functionality required, the apparatus may implement only part of the above. Certain modules of Figure 4 may be internal or connected externally, in which case they do not necessarily form integral part of the apparatus itself. E.g. display 406 may be a display that is connected to the apparatus only under specific circumstances, or the apparatus may be controlled through another device with a display, i.e. no specific display 406 and interface 405 are required for such an apparatus. Memory 411 contains software code which, when executed by processor 403, causes the apparatus to perform the methods described herein. In an exemplary embodiment, a detachable storage medium 413 such as a USB stick may also be connected. For example, the detachable storage medium 413 can hold the software code to be uploaded to memory 411. The processor 403 may be any type of processor such as a general purpose central processing unit ("CPU") or a dedicated microprocessor such as an embedded microcontroller or a digital signal processor ("DSP").

[0107] In addition, apparatus 400 may also include other components typically found in computing systems, such as an operating system, queue managers, device drivers, or one or more network protocols that are stored in memory 411 and executed by the processor 403.

[0108] The method described herein does not require any specific sensors and uses real time telemetry signals. It provides an improved solution at no additional costs.

[0109] Although aspects herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the disclosure as determined based upon the claims and any equivalents thereof.

[0110] For example, the data disclosed herein may be stored in various types of data structures which may be accessed and manipulated by a programmable processor (e.g., CPU or FPGA) that is implemented using software, hardware, or combination thereof.

[0111] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, and the like represent various processes which may be substantially implemented by circuitry.

[0112] Each described function, engine, block, step can be implemented in hardware, software, firmware, middleware, microcode, or any suitable combination thereof. If implemented in software, the functions, engines, blocks of the block diagrams and / or flowchart illustrations can be implemented by computer program instructions I software code, which may be stored or transmitted over a computer-readable medium, or loaded onto a general purpose computer, special purpose computer or other programmable processing apparatus and I or system to produce a machine, such that the computer program instructions or software code which execute on the computer or other programmable processing apparatus, create the means for implementing the functions described herein. In the present description, block denoted as "means configured to perform ..." (a certain function) shall be understood as functional blocks comprising circuitry that is adapted for performing or configured to perform a certain function. A means being configured to perform a certain function does, hence, not imply that such means necessarily is performing said function (at a given time instant). Moreover, any entity described herein as "means", may correspond to or be implemented as "one or more modules", "one or more devices", "one or more units", etc. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional or custom, may also be included. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

Claims

Claims1. A method of monitoring remaining useful life of a capacitor in an uninterruptable power supply, the method comprising: obtaining design data of the capacitor, obtaining telemetry data from the uninterruptable power supply, determining a capacitor life adjustment factor based upon the design data of the capacitor and the telemetry data of the uninterruptable power supply, wherein the capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor; determining a remaining useful life value of the capacitor based upon the capacitor life adjustment factor and a previous remaining useful life value; outputting an alert as a function of the determined remaining useful life value.

2. The method as claimed in claim 1 , comprising comparing the remaining useful life value to a predetermined threshold value; and outputting the alert when the remaining useful life value is less than the predetermined threshold value.

3. The method of claim 2, wherein the predetermined threshold value is a first predetermined threshold value, and the alert is a first alert, the method further comprising comparing the remaining useful life value to a second predetermined threshold value and outputting a second alert when the remaining useful life value is less than the second predetermined threshold value, wherein the second predetermined threshold value is less than the first predetermined threshold value.

4. The method of any of claims 1 to 3, wherein the capacitor is an aluminium electrolytic capacitor.

5. The method of any of claims 1 to 4, wherein the load percentage on the uninterruptable power supply is representative of the ratio of the power being used by a load connected to the uninterruptable power supply to the maximum power capacity that the uninterruptable power supply can handle.

6. The method of any of claims 1 to 5, wherein the capacitor life adjustment factor is representative of the remaining useful life under the current operatingconditions of the capacitor as related to the rated life at the rated operating conditions of the capacitor.

7. The method of any of claims 1 to 6, wherein the determination of the temperature factor comprises:- deriving an ambient temperature around the capacitor from an ambient temperature of the uninterruptable power supply by adding a temperature rise value, and- determining the temperature factor as a function of a comparison of the derived ambient temperature around the capacitor with a value of rated temperature of the capacitor, the temperature rise value being either a constant value included in the design data or being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, the value of rated temperature being included in the capacitor design data, and the value of the ambient temperature of the uninterruptable power supply being included in the telemetry data.

8. The method of any of claims 1 to 7, wherein the determination of the voltage factor comprises calculating the ratio of a rated voltage of the capacitor over a voltage applied across the capacitor and raising the ratio to a constant exponent, the value of the voltage applied across the capacitor being either a constant voltage value included in the capacitor design data or a measurement included in the telemetry data of the uninterruptible power supply, and the rated voltage and the constant exponent being included in the capacitor design data.

9. The method of any of claims 1 to 8, wherein the determination of the ripple current factor comprises:- determining a parameter representative of the difference between a surface temperature of an outer casing of the capacitor and an ambient temperature around the capacitor, based on a value of the ripple current flowing through the capacitor, a rated ripple current and a core temperature rise of the capacitor at the rated ripple current,- determining the ripple current factor as a function of a comparison of said parameter with the core temperature rise of the capacitor at the rated ripple current, the value of the ripple current flowing through the capacitor being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, and the rated ripple current and the core temperature rise of the capacitor at the rated ripple current being included in the capacitor design data.

10. The method of claims 7 or 9, wherein the load percentage on the uninterruptable power supply is representative of the ratio of the power being used by a load connected to the uninterruptable power supply to the maximum power capacity that the uninterruptable power supply can handle.

11. An apparatus configured to monitor remaining useful life of a capacitor in an uninterruptable power supply, the apparatus comprising means for:- obtaining design data of the capacitor,- acquiring telemetry data of the uninterruptable power supply,- determining a capacitor life adjustment factor based upon the design data of the capacitor and the telemetry data of the uninterruptable power supply, wherein the capacitor life adjustment factor comprises a voltage factor, a temperature factor and a ripple current factor;- determining a remaining useful life value of the capacitor based upon the capacitor life adjustment factor and a previous remaining useful life value;- outputting an alert as a function of the determined remaining useful life value.

12. The apparatus as claimed in claim 11 , wherein the determination of the temperature factor comprises:- deriving an ambient temperature around the capacitor from an ambient temperature of the uninterruptable power supply by adding a temperature rise value, and- determining the temperature factor as a function of a comparison of the derived ambient temperature around the capacitor with a value of rated temperature of the capacitor,- the temperature rise value being either a constant value included in the design data or being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, the value of rated temperature being included in the capacitor design data, and the value of the ambient temperature of the uninterruptable power supply being included in the telemetry data.

13. The apparatus of any of claims 10 to 12, wherein the determination of the voltage factor comprises calculating the ratio of a rated voltage of the capacitor over a voltage applied across the capacitor and raising the ratio to a constant exponent, the value of the voltage applied across the capacitor being either a constant voltage value included in the capacitor design data or a measurement included in the telemetry data of the uninterruptible power supply, and the rated voltage and the constant exponent being included in the capacitor design data.

14. The apparatus of any of claims 11 to 13, wherein the determination of the ripple current factor comprises:- determining a parameter representative of the difference between a surface temperature of an outer casing of the capacitor and an ambient temperature around the capacitor, based on a value of the ripple current flowing through the capacitor, a rated ripple current and a core temperature rise of the capacitor at the rated ripple current,- determining the ripple current factor as a function of a comparison of said parameter with the core temperature rise of the capacitor at the rated ripple current, the value of the ripple current flowing through the capacitor being interpolated from a value of load percentage on the uninterruptable power supply which is included in the telemetry data, and the rated ripple current and the core temperature rise of the capacitor at the rated ripple current being included in the capacitor design data.

15. A non-transitory computer-readable medium storing instructions thereon which when executed by one or more processors cause the one or more processors to perform the steps of the method as claimed in any of claims 1 to 10.11

Images