Abstract: A method implemented using a processor based device includes obtaining a measured electrical signal from an electrical device coupled to a mechanical device and generating a signal signature representative of a fault in the mechanical device based on the measured electrical signal. The method also includes determining a diagnostic parameter based on a harmonic frequency of the signal signature and determining the fault in the mechanical device based on the diagnostic parameter.

Abstract: Systems and methods are disclosed for on-line monitoring of the condition of the stator insulation of an AC motor or an electric generator. In certain embodiments, the system includes a transformer surrounding each pair of input and output cables associated with a given phase of power provided to the AC motor or generated by the electric generator. In another embodiment, a transformer surrounds the three input cables (for an AC motor) or the three output cables (for an electric generator) that correspond to phases of the AC motor or electric generator. In both embodiments, the transformers generate voltages that may be used to monitor leakage currents associated with the cables. A microcontroller monitors the voltages generated by the transformers and determines the condition of the stator insulation of the AC motor or the electric generator based on the voltages.

Abstract: A system configured to monitor an operating electrical device includes a testing channel coupled to the device. The device is coupled to an electric power source through at least one electric power transmission channel. The power source is configured to transmit electric power at a first frequency. The testing channel is coupled to the power transmission channel. The system also includes a signal generator coupled to the testing channel. The signal generator is configured to inject testing signals into the testing channel at a second frequency that is greater than the first frequency. The system further includes at least one apparatus magnetically coupled to the power transmission channel. The magnetically coupled apparatus is configured to present a first impedance to the electric power at the first frequency and present a second impedance to the test signals at the second frequency. The second impedance is greater than the first impedance.

Abstract: A system for monitoring a machine is provided. The system includes a digital protective relay, a communications network, and a central server. The digital protective relay is connected to the machine, and samples at least one parameter of the machine at a rate of at least about twelve samples per power cycle. The central server is located remotely from the machine for receiving the at least one parameter from the machine. The communications network provides a connection between the digital protective relay and the center server for sending a data signal representing the at least one parameter of the machine.

Abstract: A system and method for detecting a rotor fault condition in an AC induction machine is disclosed. The system includes a processor programmed to receive voltage and current data from an AC induction machine, generate a current frequency spectrum from the current data, and identify rotor-fault related harmonics in the current frequency spectrum. The processor is also programmed to calculate a fault severity indicator using the voltage and current data, identified rotor-fault related harmonics, and motor specifications, analyze the fault severity indicator to determine a possibility of rotor fault. The processor generates an alert based on the possibility of rotor fault.

Abstract: A method of detecting faults in a wind turbine generator based on current signature analysis is disclosed herein. The method includes acquiring a set of electrical signals representative of an operating condition of a generator. Further, the electrical signals are processed to generate a normalized spectrum of electrical signals. A fault related to a gearbox or bearing or any other component associated with the generator is detected based on analyzing the current spectrum.

Abstract: A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.

Abstract: A system and method for detecting a rotor fault condition in an AC induction machine is disclosed. The system includes a processor programmed to receive voltage and current data from an AC induction machine, generate a current frequency spectrum from the current data, and identify rotor-fault related harmonics in the current frequency spectrum. The processor is also programmed to calculate a fault severity indicator using the voltage and current data, identified rotor-fault related harmonics, and motor specifications, analyze the fault severity indicator to determine a possibility of rotor fault. The processor generates an alert based on the possibility of rotor fault.

Abstract: A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

Abstract: A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

Abstract: A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.

Abstract: A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

Abstract: A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.