Smart capacitor

Methods and systems include identifying an abnormal condition in a PFC circuit comprising an input configured to be coupled to a 3-phase power source and to receive input 3-phase power from the 3-phase power source, a bus having a plurality of bus lines, each bus line configured to be coupled to the input and to carry one phase of the input 3-phase power, a PFC leg including a contactor configured to selectively couple a capacitor bank included in the PFC leg to the bus. In response to identifying the abnormal condition, the contactor is controlled to decouple the capacitor bank from the bus, and after a reset button has been activated, the contactor is recoupled to the capacitor bank to resume operating the PFC leg to provide power factor correction to the input 3-phase power.

BACKGROUND

Field

Embodiments generally relate to three-phase Power Factor Correction (PFC) circuits.

Discussion of Related Art

Power factor, the ratio between the real power and the apparent power drawn by electrical loads coupled to a power system, can be utilized as a measure of the efficiency of the power system. For example, in an ideal system, the power factor is close to unity. Power Factor Correction (PFC) systems can be utilized in a power system to raise power factor of the system closer to unity in order to improve efficiency of the system.

Three-phase power systems typically include PFC equipment that is configured to apply power factor correction to received 3-phase input power to reduce reactive power requirements and associated losses. Such PFC equipment commonly includes switching circuitry that is operated by a controller, in conjunction with a capacitor bank, to provide the power factor correction.

SUMMARY

Aspects and embodiments are directed to a capacitor system comprising a housing, the housing including at least one capacitor configured to be coupled to at least one bus line, at least one sensor configured to measure at least one electrical parameter of the at least one capacitor; and a monitoring device configured to monitor the at least one electrical parameter, identify one or more conditions of the at least one capacitor based on the at least one electrical parameter, and operate a contactor to decouple the at least one capacitor from the at least one bus line in response to identifying the one or more conditions.

According to one embodiment, the at least one sensor includes a voltage sensor coupled to the at least capacitor and the at least one parameter includes a voltage across the at least one capacitor. In some embodiments the one or more conditions include the voltage exceeding a predetermined value. In additional embodiments the one or more conditions include the voltage exceeding the predetermined value for one of at least a number of samples and at least a period of time.

According to another embodiment, the at least one sensor includes a current sensor coupled to the at least one capacitor and configured to measure current provided to the at least one capacitor. In some embodiments the one or more conditions include the current exceeding a predetermined value. In additional embodiments the one or more conditions include the current exceeding the predetermined value for one of at least a number of samples and at least a period of time. In other embodiments, the one or more conditions include the current being less than a second predetermined value for one of at least a number of samples and at least a period of time.

According to one embodiment, in operating the contactor to decouple the at least one capacitor from the at least one bus, the monitoring device is further configured to, in response to identifying the one or more conditions, transmit a signal through one or more of a wired or wireless connection to a controller to operate the contactor to decouple the system from the at least one bus line.

According to another embodiment, the system further comprises a trip indicator including a reset button configured to be activated to recouple the at least one capacitor to the at least one bus line and continue monitoring for the one or more conditions, and the monitoring device is further configured to transmit a signal to the trip indicator in response to identifying the one or more conditions.

According to one embodiment, the at least one sensor includes a voltage sensor coupled to the at least one capacitor and configured to measure a voltage across the at least one capacitor, and a current sensor coupled to the at least one capacitor and configured to measure current provided to the at least one capacitor, the at least one parameter includes the voltage and the current, and the one or more conditions include an overvoltage, an overcurrent, and an undercurrent. The monitoring device is further configured to detect the voltage exceeds the predetermined value for one of at least a number of samples and at least a period of time, and identify the overvoltage, detect the current exceeds a second predetermined value for one of at least a number of samples and at least a period of time, and identify the overcurrent, and detect the current is less than a third predetermined value for one of at least a number of samples and at least a period of time, and identify the undercurrent.

Aspects and embodiments are directed to a method of operating a capacitor system including a housing, the housing including at least one capacitor, at least one sensor, and a monitoring device. The method comprises coupling the at least one capacitor to at least one bus line, coupling the at least one capacitor to the at least one sensor, measuring, with the at least one sensor, at least one electrical parameter of the at least one capacitor, monitoring, with the monitoring device, the at least one electrical parameter, identifying one or more conditions of the at least one capacitor based on the at least one electrical parameter, and operating a contactor to decouple the at least one capacitor from the at least one bus line in response to identifying the one or more conditions.

According to one embodiment, the method further comprises coupling the at least one sensor to the at least one capacitor. Measuring the at least one parameter includes measuring a voltage across the at least one capacitor, determining the voltage exceeds a predetermined value for one of at least a number of samples and at least a period of time, and identifying the one or more conditions includes identifying an overvoltage.

According to another embodiment, the method further comprises coupling the at least one sensor to the at least one capacitor, measuring the at least one parameter includes measuring a current provided to the at least one capacitor, determining the current exceeds a predetermined value for one of at least a number of samples and at least a period of time, and identifying the one or more conditions includes identifying an overcurrent.

According to one embodiment, the method further comprises coupling the at least one sensor to the at least one capacitor, measuring the at least one parameter includes measuring a current provided to the least one capacitor, determining the current is less than a predetermined value for one of at least a number of samples and at least a period of time, and identifying the one or more conditions includes identifying an undercurrent.

According to another embodiment, operating the contactor to decouple the at least one capacitor from the at least one bus further comprises, in response to identifying the one or more conditions, transmitting a signal through one or more of a wired or wireless connection to a controller, and operating, with the controller, the contactor to open in response to receiving the signal.

According to one embodiment, the method further comprises, in response to identifying the one or more conditions, transmitting a signal to a trip indicator included in the capacitor system, the trip indicator including a reset button, in response to receiving the signal, activating the trip indicator, and in response to the reset button being activated, recoupling the smart capacitor system to the at least one bus and continuing to monitor for the one or more conditions.

Aspects and embodiments are directed to a Power Factor Correction (PFC) circuit comprising a controller, an input configured to be coupled to a 3-phase power source and to receive input 3-phase power from the 3-phase power source, at least one bus configured to carry the input 3-phase power, a PFC leg including a contactor configured to be coupled to a capacitor system, the contactor coupled to the controller and configured to couple the PFC leg to the at least one bus, the capacitor system including a housing. The housing includes at least one capacitor configured to be coupled to the at least one bus line, at least one sensor configured to measure at least one electrical parameter of the at least one capacitor, and a monitoring device configured to monitor the at least one electrical parameter, identify one or more conditions of the at least one capacitor based on the at least one electrical parameter, and transmit a signal to the controller to operate the contactor to decouple the at least one capacitor from the at least one bus line based on identifying the one or more conditions.

According to one embodiment, the PFC circuit further comprises a trip indicator including a reset button configured to be activated to recouple the at least one capacitor to the at least one bus line and continue monitoring for the one or more conditions, and the monitoring device is further configured to transmit a signal to the trip indicator in response to identifying the one or more conditions.

According to another embodiment, the at least one sensor includes a voltage sensor coupled to the at least one capacitor and configured to measure a voltage across the at least one capacitor, and a current sensor coupled to the at least one capacitor and configured to measure current provided to the at least one capacitor, the at least one parameter includes the voltage and the current, the one or more conditions include an overvoltage, an overcurrent, and an undercurrent, and the monitor is further configured to detect the voltage exceeds the predetermined value for one of at least a number of samples and at least a period of time, and identify the overvoltage, detect the current exceeds a second predetermined value for one of at least a number of samples and at least a period of time, and identify the overcurrent, and detect the current is less than a third predetermined value for one of at least a number of samples and at least a period of time, and identify the undercurrent.

DETAILED DESCRIPTION

It is to be appreciated that embodiments of the methods and systems discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and systems are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements and features discussed in connection with any one or more examples are not intended to be excluded from a similar role in any other examples. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are no intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms in this document and documents incorporated herein by reference, the term usage in the incorporated features is supplementary to that of this document; for irreconcilable differences, the term usage in this document controls.

As described above, a power factor correction circuit of a three-phase power system typically includes switching circuitry that is operated by a controller, in conjunction with a capacitor bank, to provide power factor correction to received input three-phase power. However, abnormal voltage and/or current conditions received by the power factor correction circuit and capacitor bank may have a negative impact on capacitors in the capacitor bank. For example, an abnormal condition such as an overvoltage or overcurrent condition can reduce the lifetime of the capacitors in the capacitor bank. In addition, a resulting loss of capacitance of the capacitors in the capacitor bank can cause an undercurrent condition which can reduce efficiency of the system and/or affect operation of a corresponding load.

Aspects and embodiments describe herein are related to a smart capacitor system capable of detecting an abnormal voltage and/or current condition of a capacitor in the system, and as a result, operating a contactor to prevent power flow to the capacitor. By preventing power flow from the contactor to the capacitor in response to detecting an abnormal condition, the lifetime of the capacitor can be preserved and the efficiency of the system can be maintained.

An example of such a smart capacitor system110in a configuration of connected components is illustrated inFIG.1. This configuration includes a power system120, at least one contactor106, and a controller109. The power system120is configured to be connected to the contactor106, which is configured to be coupled to the smart capacitor system210. The controller109can be connected to the contactor106and/or the smart capacitor system110. When in use, the power system120can store energy in one or more internal capacitors of the capacitor system210. The smart capacitor110110monitors parameters of the one or more internal capacitors and either operates directly, or instructs the controller109to operate, the contactor106to decouple the smart capacitor110from the power system120in response to certain conditions.

Capacitor systems described herein can be utilized in a PFC circuit. For example,FIG.2is a schematic diagram of a PFC circuit100according to embodiments described herein. The PFC circuit100includes an input101, input power lines102, a bus104, an input circuit breaker105, a controller209(e.g., similar to the controller109inFIG.1), an input neutral line (N), an input ground line (PE), and at least one PFC leg107, each PFC leg107including a circuit breaker103, a leg contactor206(e.g., similar to the contactor106inFIG.1), an inductor bank108, and a smart capacitor system210(e.g., similar to the smart capacitor system110inFIG.1). As shown inFIG.1, the PFC circuit100includes three PFC legs107; however, in other embodiments, the PFC circuit100includes more or fewer than three PFC legs107. The input lines102include three input phase lines (L1, L2, L3). Each PFC leg107is configured to be coupled to the bus104.

The input101of the PFC circuit103is configured to be coupled to a 3-phase power source via input power lines102and to receive input 3-phase power from the 3-phase power source. Each input power line102configured to carry one phase of the input 3-phase power. The input circuit breaker105of the PFC circuit103is configured to selectively couple each input power line102to a corresponding bus line (BL1, BL2, BL3) of the bus104, via the input101.

The PFC leg circuit breaker103is configured to be coupled to each bus line (BL1, BL2, BL3) of the bus104and the leg contactor206. Each leg contactor206is configured to selectively couple each bus line (BL1, BL2, BL3) of the bus104to the capacitor system210via a corresponding inductor in the inductor bank108. As shown inFIG.1, each PFC leg107includes one leg contactor206; however, in other embodiments, each PFC leg107can include more than one leg contactor206. The controller209is coupled to the capacitor system210and leg contactor206of each PFC leg107. In some embodiments, the capacitor system210is in communication with the controller209to indicate abnormal voltage and/or current conditions of the capacitor system210.

As similarly described above, the PFC circuit100is operated by the controller209to provide power factor correction to the input 3-phase power received by the input lines102. By selectively coupling desired PFC legs107to the bus104, the controller209can operate the PFC circuit100to provide desired power factor correction to the received input 3-phase power.

The capacitor system210of each PFC leg107is configured to monitor voltage across the capacitor system210and/or current provided to the capacitor system210and, as a result, detect abnormal voltage and/or current conditions. In response to detecting an abnormal voltage and/or current condition at the capacitor system210, the capacitor system can generate a signal indicating as such.

According to one embodiment, the capacitor system210provides the signal indicating the abnormal voltage and/or current condition to the controller209. In response to receiving a signal from the capacitor system210indicating an abnormal voltage and/or current condition, the controller209operates a leg contactor206of the PFC leg107within which the abnormal condition was detected to open such that the PFC leg107(and corresponding capacitor system210) is decoupled from the bus104. In another embodiment, the capacitor system210can directly operate a corresponding leg contactor206to open, thereby decoupling the capacitor system210from the bus104.

By decoupling the capacitor system210from the bus104(and preventing power flow to/from the capacitor system210) in response to a detected abnormal voltage and/or current condition, the lifetime of capacitors in the capacitor system210can be preserved and the efficiency of the PFC circuit100can be maintained.

FIG.3is a schematic diagram of one embodiment of the capacitor system210in one of the PFC legs107in accordance with aspects described herein. As illustrated inFIG.2, the capacitor system210includes control power lines231,233, and a housing210. Within the housing210, the capacitor system210includes a trip indicator212(e.g., a visual or audible alarm), a monitoring device214, a relay217, a capacitor bank218including a plurality of capacitors251,252,253, a temperature sensor220, a battery222, and a sensor package216. In one embodiment, the capacitors of the capacitor bank218are oriented in a delta configuration; however, in other embodiments, the capacitors may be configured differently.

The battery222is coupled to the monitoring device214and is configured to supply power to the monitoring device214.

The control power lines231,233are configured to provide power to the monitoring device214. In the event of one or more of the capacitors251,252,253being disconnected from a supply line, the power provided by the control power lines231,233can keep the monitoring device214powered and running to perform one or more operations including blinking indicator lights, communicating with externally connected devices, logging data, and holding or changing the state of the relay217.

As illustrated inFIG.3, the sensor package216includes three voltage sensors (shown as solid black dots) and three current transformers (shown as ovals). Each sensor in the sensor package216is coupled to the monitoring device214. A pair of sensors (one current sensor and one voltage sensor) is coupled to each of three capacitors251,252,253in the capacitor bank218. One terminal of the first capacitor251is coupled to a node shared by a terminal of the third capacitor253, the node being coupled to a first pair of sensors (one voltage sensor and one current sensor). Another terminal of the first capacitor251is coupled to a node shared by a terminal of the second capacitor252, the node being coupled to a second pair of sensors (one voltage sensor and one current sensor). Another terminal of the second capacitor252is coupled to a node shared by another terminal of the third capacitor253, the node being coupled to a third pair of sensors (one voltage sensor and one current sensor).

Other configurations of sensors are contemplated. In an example, the housing210includes only current sensors coupled to the capacitor bank218. In another example, the housing210includes only voltage sensors coupled to the capacitor bank.

As shown inFIG.3, the capacitors251,252,253are in a delta configuration. However, in other embodiments, the capacitors251,252,253can be configured differently. For example, in one embodiment, the capacitors251,252,253are configured in a star configuration such that a terminal of each capacitor is coupled to a central node. Some examples include only current sensors. Other examples include only voltage sensors.

As shown inFIG.3, the voltage sensors are coupled to each capacitor251,252,253and are configured to monitor the voltage across each capacitor251,252,253. The current sensors are coupled to each capacitor251,252,253and are configured to monitor the current provided to each capacitor251,252,253. In at least one embodiment, in response to detecting an abnormal voltage (e.g., an overvoltage or an undervoltage) and/or current condition (e.g., an overcurrent or an undercurrent) at the capacitors251,252,253, the monitoring device214transmits a signal to the controller209indicating as such. In one embodiment, the monitoring device214communicates wirelessly with the controller209. In another embodiment, the monitoring device214communicates with the controller209via a wired connection (e.g., a serial communication bus, not shown).

According to one embodiment, the monitoring device214identifies an abnormal condition upon sensing a voltage across one or more of the capacitors251,252,253above a threshold level (i.e., an overvoltage condition). In another embodiment, the monitoring device214identifies an abnormal condition upon sensing current to one or more of the capacitors251,252,253above a threshold level (i.e., an overcurrent condition). In another embodiment, the monitoring device214identifies an abnormal condition upon sensing current to one or more of the capacitors251,252,253below a threshold level (i.e., an undercurrent condition). According to one embodiment, in response to identifying an abnormal condition, the monitoring device214transmits a signal identifying as such to the controller209, which is external the housing210, and the controller209operates the leg contactor206, which is also external to the housing202of the monitoring device214, to decouple the corresponding PFC leg107from the bus104. In another embodiment, in response to identifying the abnormal condition, the monitoring device214operates the leg contactor206directly through one of a wired or wireless connection, thereby opening the leg contactor206.

In at least one embodiment, the controller209is configured to control the leg contactor (contactor)206via one or more of the signal lines226. The leg contactor206includes an inductor that is configured to generate a magnetic field capable of operating one or more contact switches within the contactor206. For example, when a voltage is applied to a terminal of the inductor of the leg contactor206via the one or more signal lines226, a magnetic field is generated by the inductor that operates one or more contact switches within the leg contactor206to change from one state to another (e.g., open to closed, or closed to open), thereby decoupling the PFC leg107from the bus104.

In addition, the controller209can be coupled to any one or more components within the housing210via the one or more signal lines224. For example, in one embodiment, the controller209is coupled to the monitoring device214via the one or more signal lines224and is configured to communicate (bi-directionally and/or unidirectionally) with the monitor214via the signal lines224. In one embodiment, the signal lines224provide a wired connection (e.g., a serial communication bus. The signal lines may alternatively or in addition be a wireless connection (e.g., a particular radio frequency, Wi-Fi, or Bluetooth).

Upon receiving a signal from the monitoring device214indicating an abnormal condition, the controller209operates the leg contactor206of the PFC leg107within which the abnormal condition was detected to open such that the PFC leg107(and corresponding capacitors in the capacitor bank218) is decoupled from the bus104. Such overvoltage, overcurrent, or undercurrent conditions, as described above, can reduce the lifetime of the capacitors251,252,253and reduce efficiency of the capacitor system210in the housing210. Accordingly, by decoupling the capacitors251,252,253from the bus104in response to a detected abnormal voltage and/or current condition, the lifetime of the capacitors251,252,253can be preserved. When incorporated into a PFC circuit, including the PFC circuit100illustrated inFIG.1, such decoupling maintains efficiency of the PFC circuit.

Additional embodiments include the monitoring device214controlling, in response to identifying an abnormal condition, the leg contactor206directly via a signal line without first communicating with the controller209. For example, in some embodiments, the monitoring device214is configured to control the leg contactor206directly via the relay217by closing the relay217such that a voltage is applied to the inductor of the leg contactor206to generate a magnetic field that operates one or more contact switches within the leg contactor206to decouple the PFC leg107from the bus104.

According to one embodiment, the monitoring device214is further configured to monitor ambient temperature of the housing210. The temperature sensor220is coupled to the monitoring device214and is configured to measure a temperature within the housing210. The monitoring device214is configured to identify an abnormal condition based on the monitored temperature. In some embodiments, the temperature sensor220is within the housing210, as illustrated inFIG.2. In other embodiments, the monitored temperature is external to the housing210(not shown). According to certain embodiments, the controller209or the monitoring device214is configured to obtain a temperature value from the temperature sensor220, compare the value to a predetermined threshold, and determine an abnormal condition. In an example, in response to the temperature sensor220measuring a value exceeding the predetermined threshold, the leg contactor206is controlled to decouple the PFC leg107from the bus104. The trip indicator212is configured to activate in response to the monitoring device214and/or the controller209detecting an abnormal condition and decoupling the capacitor bank218from the bus104. In another embodiment, the trip indicator212includes a reset button that, once activated by a user, causes the monitoring device214to recouple the capacitor bank218to the bus104and continue monitoring for abnormal conditions.

As described above, the capacitor system210including the housing210is utilized in a 3-phase power system; however, in other embodiments, the housing210is utilized in a system with fewer than three phases or in a different type of system.

According to some embodiments, the controller209is configured to monitor and control operation of each PFC leg107in the PFC circuit100. Using data stored in associated memory, the controller209is operable to execute one or more instructions that may result in the manipulation of one or more switches' conductive states. In some examples, the controller209includes one or more processors or other types of controllers. The controller209may perform a portion of the functions discussed herein on a processor, and perform another portion using an Application-Specific Integrated Circuit (ASIC) tailored to perform particular operations. Examples in accordance with aspects and embodiments described herein may perform the operations described herein using many specific combinations of hardware and software and are not limited to any particular combination of hardware and software components.

FIG.4is a flow chart illustrating a method300of monitoring one or more capacitors. The method300includes the acts302,304,308,310, and314, as well as the conditions306and312. According to certain embodiments, the entirety of the method300, or any subset of acts or conditions thereof are performed by a processor or a controller, including, for example, the controller209. According to additional embodiments, the entirety of the method300, or any subset of acts or conditions thereof are performed by the monitoring device214. Other embodiments include the method300being implemented by a combination of the controller209and the monitoring device214.

The method300begins with act302, which operates a PFC circuit, such as the PFC circuit100to provide power factor correction to input 3-phase power received by an input of the PFC circuit. For example, in one embodiment, the controller209operates the three PFC legs107of the PFC circuit100illustrated inFIG.1to provide power factor correction to input 3-phase power received by the PFC circuit100.

In act304, while the PFC circuit100is providing power factor correction to the input 3-phase power received by the input101, the voltage across and/or current provided to one or more capacitors251,252,253in the capacitor bank218is monitored. In an example, the monitoring device214monitors the voltage and/or current. In another example, the monitoring device214receives data from the sensor package216and provides the data to the controller209for monitoring the voltage and/or current.

In one embodiment, the controller209and/or the monitoring device214determines, at condition306, if one or more abnormal conditions has occurred based on one or more values of monitored current and/or voltage obtained in act304. In one embodiment, an abnormal overvoltage condition is identified as existing, at condition306, in response to identifying that the monitored voltage is greater than a voltage threshold. In another embodiment, an abnormal overcurrent condition is identified as existing, at condition306, in response to the monitored current being greater than a current threshold. In another embodiment, an abnormal undercurrent condition is identified as existing, at condition306, in response to identifying that the monitored current is less than a current threshold. If an abnormal condition is not identified, the capacitor system210remains coupled to the bus104and the controller209and/or the monitoring device214continues to monitor for abnormal conditions. In response to determining an abnormal condition at the condition306(i.e., YES in condition306), the method300proceeds to act308.

In act308, in response to the controller209and/or the monitoring device214identifying the abnormal condition, the corresponding leg contactor of the PFC leg containing the capacitor with the abnormal condition is instructed to open, thereby decoupling the capacitor system210from the bus104. By decoupling the capacitor system210from the bus104(and preventing power flow to/from the capacitor system210) in response to a detected abnormal voltage and/or current condition, the lifetime of capacitors in the capacitor system210can be preserved and the efficiency of the PFC circuit100can be maintained.

According to certain embodiments, upon the abnormal condition being identified and the capacitor system210including the capacitor bank218being decoupled from the bus104, the trip indicator212is activated in act310. In one embodiment, the monitoring device214or the controller209activates the trip indicator212(e.g., a visual or audible indicator) to provide a user with an indication of the fault indicated by the identified abnormal condition.

According to additional embodiments, upon the abnormal condition being identified and the capacitor system210being decoupled from the bus104areset switch/button is monitored, at condition312, to determine if the reset switch/button has been activated by a user. If the reset switch/button is not activated, the reset switch/button is further monitored for activation while the capacitor system210and the capacitor bank218remains decoupled from the bus104. Upon activation of the reset switch or button, the method300proceeds to act314where the leg contactor that was opened in act308is closed, thereby recoupling the PFC leg that experienced the abnormal condition to the bus104.

In certain embodiments, the controller209and/or the monitoring device214is configured to control the leg contactor of a different PFC leg in the PFC circuit100. As an example, as illustrated inFIG.2, one of the three PFC legs107includes the monitoring device214, which detects an abnormal condition in its respective PFC leg and controls the leg contactor of one or more other PFC legs of the three PFC legs to decouple from the bus104. Additional embodiments include the monitoring device214in one PFC107controlling one or more leg contactors in the PFC circuit to recouple to the bus104. The monitoring device214may control the one or more leg contactors directly or instruct the controller209to carry out the decoupling or recoupling.

FIG.5is a flow chart illustrating a method400of monitoring one or more capacitors. The method400includes the acts402,404,406,408,410, and414, as well as the conditions416,418,420,422,424,426, and412. According to certain embodiments, the entirety of the method400, or any subset of acts or conditions thereof are performed by a processor or a controller, including, for example, the controller209and the controller209. According to additional embodiments, the entirety of the method400, or any subset of acts or conditions thereof are performed by the capacitor system210or the monitoring device214. Examples of the method400include controlling one or more components within the housing210and/or the leg contactor206. Other examples of the method400include controlling one or more components of the PFC circuit100. For the sake of brevity, the method400is described where it primarily differs from the discussed above with respect to the method300. According to certain embodiments, the entirety of the method400or any subset of acts or conditions thereof are implemented by the controller209and/or the monitoring device214.

As illustrated inFIG.5, the method400monitors both capacitor voltage in act404and capacitor current in act406. According to other embodiments, the method400can include only one of acts404and406(and their corresponding conditions416and416, or424and426). In each of the conditions416,420,424a measured value is compared to a predetermined threshold. For example, one or more voltage sensors, at condition416, determine a voltage across a capacitor within a capacitor bank. If the voltage exceeds a predetermined threshold (i.e., an overvoltage), then the method400proceeds to an additional condition418. In response to any of conditions416,420, and424being satisfied for a sufficiently long period of time and/or for a sufficient number of samples, an abnormal condition is identified at conditions418,420, and424, respectively.

In an example, a controller, including, the controller209and/or the monitoring device214, determines that a voltage value across one of the capacitors251,252,253in the capacitor bank218is greater than a predetermined voltage value at condition416. However, in response to condition416being satisfied for only one sample, for example, an overvoltage condition is not indicated, at condition418, and the capacitor voltage would continue to be monitored in the act416until the condition418is satisfied for a predetermined number of samples, for example, five samples. In another example, the method400only proceeds to act408when the voltage is greater than a threshold value of voltage for at least a predetermined period of time, at condition418.

In another example, the controller209and/or the monitoring device214determines that a current value provided to one of the capacitors251,252,253in the capacitor bank218is greater than a predetermined current value at condition420. However, in response to condition420being satisfied for only one sample, for example, an overcurrent condition is not indicated, at condition422, and the capacitor current would continue to be monitored in the act420until the condition422is satisfied for a predetermined number of samples, for example, five samples. In another example, the method400only proceeds to act408when the current is greater than a threshold value of current for at least a predetermined period of time, at condition422.

In another example, the controller209and/or the monitoring device214determines that a current value provided to one of the capacitors251,252,253in the capacitor bank218is less than a predetermined current value at condition424. However, in response to condition424being satisfied for only one sample, for example, an undercurrent condition is not indicated, at condition426, and the capacitor current would continue to be monitored in the act406until the condition424is satisfied for a predetermined number of samples, for example, five samples. In another example, the method400only proceeds to act408when the current is less than a threshold value of current for at least a predetermined period of time, at condition426. According to additional embodiments, one or more of the conditions416,420, and424determines an additional condition where the absolute value between the monitored value and the respective threshold must meet or exceed a minimum value. In such embodiments, the subsequent conditions418,422, and426may have different values than those described above. In an example, the condition416determines that the monitored capacitor voltage is not only greater than a predetermined threshold, but greater than the predetermined threshold by a minimum absolute amount value of voltage. Such examples provide additional options to tune the method400to a particular application by balancing a tradeoff between how long the monitored value needs to satisfy the conditions of416,420, and424and how large of a difference with a nominal value can be tolerated. According to some embodiments, larger differences with nominal values in the conditions416,420, and424require shorter periods of time or numbers of samples in the conditions418,422,426.

One embodiment of a smart capacitor system610(e.g., similar to the smart capacitor system210) is shown inFIGS.6A,6B, and6C. The capacitor system610is a box-type capacitor. However, additional embodiments include other types of capacitors including, but not limited to, can-type capacitors. The capacitor system610includes a cover, which includes a first panel621, a second panel622, a third panel623, a fourth panel624, and a fifth panel625, each panel can be removable for more access to the internal components. As illustrated inFIG.6B, the fifth panel625includes a grommet608, which allows one or more power cables to pass through.

Also included in the capacitor system610is a first terminal601, a second terminal602, and a third terminal603, each terminal being adjacent to a region606. Similar to the PFC circuit100, each of the terminals601,602,603is configured to be part of a PFC circuit (not shown) and connected to one of three power lines (e.g., similar to the bus lines104, the phase lines102, or some other power lines), which are each configured to be connected to a separate PFC leg (e.g., similar to the PFC leg107). One or more of the internal components of the capacitor system610may be located within the region606. In an example, the region606includes a monitoring device (e.g., similar to the monitoring device214) that is adjacent and connected to the terminals601,602,603. For example, the monitoring device can include current sensors and/or voltage sensors which are arranged to monitor the terminals for the one or more conditions as described herein. According to certain embodiments, the monitoring device is externally connected to the internal capacitors of the capacitor system610as a standalone unit.

Embodiments of the capacitor systems110,210,610include reactive power ratings ranging from 2.5 KVAR to 100 KVAR, rated voltages ranging from 240 V to 830 V, and network frequencies including 50 Hz and 60 Hz. It is contemplated that the monitoring device may be incorporated into any number, size, and type of capacitors, including any obvious variants thereof.

As described above, a power factor correction circuit is provided that is capable of detecting an abnormal voltage and/or current condition in a three-phase system, and as a result, operating a contactor to prevent power flow to capacitors in the capacitor bank of the power factor correction circuit. By preventing power flow from the contactor to the capacitors in response to detecting an abnormal condition, the lifetime of the capacitors in the capacitor bank can be preserved and the efficiency of the system can be maintained.

Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of aspects and embodiments described herein. Accordingly, the foregoing description and drawings are by way of example only