System and method for exchangeable capacitor modules for high power inverters and converters
View Patent ↗A method of and system for monitoring condition of a large capacitor connected across an output of a rectifier circuit in an operating electrical power transmission circuit in order to anticipate capacitor failure and facilitate appropriate corrective action is disclosed. The method includes measuring a ripple voltage on the capacitor and ripple current through the capacitor, determining from a representative signal whether the signal exceeds a predetermined threshold; and sending an output to a controller on a system operator if the signal exceeds the predetermined threshold. The ripple current and ripple voltage measurements may be provided as inputs to a digital to analog converter which produces and sends the representative signal to a microprocessor to generate the output to the controller.
1. A method comprising:
providing a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;
measuring a ripple voltage on the capacitor;
measuring a ripple current through the capacitor;
determining a representative signal from the ripple voltage and current measurements;
determining whether the signal exceeds a predetermined threshold; and
sending an output to a controller if the signal exceeds the predetermined threshold.
2. The method according to claim 1 wherein the ripple current and ripple voltage measurements are provided as inputs to a digital to analog converter and wherein the converter produces and sends the representative signal to a microprocessor to generate the output to the controller.
3. The method according to claim 1 wherein the measuring of ripple current is performed by a rectifier and amplifier module to produce a direct current representative signal.
4. The method according to claim 1 wherein the measuring of ripple voltage is performed by a voltage divider module.
5. The method according to claim 2 further comprising sensing a temperature of the capacitor and sending a temperature signal to the digital to analog converter.
6. The method according to claim 2 further comprising recommending to a master module replacing the capacitor when the controller receives an output from the microprocessor.
7. A power inverter comprising:
a box housing an electrical circuit therein including a dc to ac converter;
at least one electrolytic capacitor mounted to an exterior of the box, the capacitor being connected with the electrical circuit within the box, the capacitor including a cutout switch for selectively removing the capacitor from electrical connection to the circuitry within the box; and
a capacitor health monitoring circuit operably connected to the capacitor to measure a ripple voltage on the capacitor, and
measure a ripple current through the capacitor.
8. The inverter according to claim 7 wherein the monitoring circuit includes a microprocessor programmed to perform operations of:
determining a representative signal from the ripple voltage and current measurements;
determining whether the signal exceeds a predetermined threshold; and
sending an output to a controller if the signal exceeds the predetermined threshold.
9. The inverter according to claim 7 wherein the ripple current and ripple voltage are analyzed in a microprocessor programmed to compare a signal representative of the ripple current and ripple voltage to a predetermined threshold.
10. The inverter according to claim 9 wherein the monitoring circuit issues an output signal when the ripple current and ripple voltage exceed the predetermined threshold.
11. The inverter according to claim 7 wherein the health monitoring circuit has a current sensor in series with the capacitor.
12. The inverter according to claim 7 wherein the health monitoring circuit is connected in parallel with the capacitor.
13. The inverter according to claim 7 wherein the health monitoring circuit includes a temperature sensor operable to sense ambient temperature around the capacitor.
14. A health monitoring system, the system comprising:
a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;
a ripple voltage detector connected across the capacitor;
a ripple current detector connected in series with the capacitor;
a measuring module connected to the voltage and current detectors operable to produce a signal representative of the ripple voltage and current and send an output to a controller if the signal exceeds a predetermined threshold.
15. The system according to claim 14 wherein the measuring module includes an analog-to-digital converter connected to a microprocessor which generates the output to the controller.
16. The system according to claim 14 wherein the ripple voltage detector is a voltage divider module.
17. The system according to claim 16 wherein the ripple current detector is a rectifier and amplifier module.
18. The system according to claim 17 wherein outputs of the voltage divider module and rectifier and amplifier module are fed to an analog-to-digital converter.