Variable frequency drive and methods for filter capacitor fault detection
AssigneeRockwell Automation Technologies, Inc.
InventorsYuan Xiao, Navid Zargari, Manish Pande, Vijay Khatri
Life of this patent
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Abstract
Variable frequency motor drives and control techniques are presented in which filter capacitor faults are detected by measuring filter neutral node current and/or voltages and detecting changes in the fundamental frequency component of the measured neutral condition at the fundamental frequency of the input power and/or based on input current unbalance.
Claims28
A variable frequency drive for powering a load, comprising:
- a rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output with first and second DC output nodes, and a rectifier network coupled between the AC input nodes and the DC output nodes and providing rectified DC electrical power at the DC output nodes;
- an intermediate DC circuit comprising first and second DC current paths and at least one electrical storage component;
- an inverter comprising an AC output with a plurality of AC output nodes for supplying power to a load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths of the intermediate DC circuit and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal to provide variable frequency AC electrical power to the load;
- at least one filter circuit comprising a plurality of filter capacitors coupled to a neutral node;
- a feedback circuit providing at least one neutral feedback signal or value based on a sensed condition of the neutral node;
- a control system, with an inverter control component operative to provide the inverter switching control signals to cause the inverter to selectively convert DC current from the intermediate DC circuit to provide AC electrical power to the AC output according to at least one setpoint signal or value;
- and
- a capacitor fault detection circuit receiving the at least one neutral feedback signal or value from the feedback circuit and operative to extract a measured fundamental frequency component from the at least one neutral feedback signal or value at a fundamental frequency of the AC electrical input power, and to determine whether a fault condition is suspected in at least one of the filter capacitors based at least partially on the measured fundamental frequency component.
A method for detecting filter capacitor faults in a variable frequency drive, the method comprising:
- measuring at least one condition of a neutral node coupled to a plurality of filter capacitors of at least one filter circuit of a variable frequency drive;
- extracting a measured fundamental frequency component from the at least one measured neutral condition at a fundamental frequency of AC electrical input power provided to the variable frequency drive;
- and
- determining whether a fault condition is suspected in at least one of the filter capacitors based at least partially on the measured fundamental frequency component.
A non-transitory computer readable medium with computer executable instructions for detecting filter capacitor faults in a variable frequency drive, the computer readable medium comprising computer executable instructions for:
- measuring at least one condition of a neutral node coupled to a plurality of filter capacitors of at least one filter circuit of a variable frequency drive;
- extracting a measured fundamental frequency component from the at least one measured neutral condition at a fundamental frequency of AC electrical input power provided to the variable frequency drive;
- and
- determining whether a fault condition is suspected in at least one of the filter capacitors based at least partially on the measured fundamental frequency component.
Dependencies are inferred from the claim text.