Michael J. Devaney

Bearing damage detection via wavelet packet decomposition of the stator current

Bearing faults are one of the major causes of motor failures. The bearing defects induce vibration, resulting in the modulation of the stator current. In this paper, the stator current is analyzed via wavelet packet decomposition to detect bearing defects. The proposed method enables the analysis of frequency bands that can accommodate the rotational speed dependence of the bearing defect frequencies. The wavelet packet decomposition also provides a better treatment of nonstationary stator current than currently used Fourier techniques.

Power measurement using the wavelet transform

This paper provides the theoretical basis for and demonstrates the practical application of power and rms measurements directly from the wavelet transform data associated with each voltage current element pair. The voltage and current wavelet transforms are derived from concurrent measurements using a common orthonormal wavelet basis. The advantage of using the wavelet transform data directly is that it provides the distribution of the power and energy with respect to the individual frequency bands associated with each level of the wavelet analysis. Frequency separation into the various wavelet levels is achieved using IIR filters because their magnitude characteristics are much better than typical FIR filters of equivalent complexity. The IIR polyphase network strategy yields a simpler wavelet filter bank design.

Reactive power measurement using the wavelet transform

This paper provides the theoretical basis for the measurement of reactive and distortion powers from the wavelet transforms. The measurement of reactive power relies on the use of broad-band phase-shift networks to create concurrent in-phase currents and quadrature voltages. The wavelet real power computation resulting from these 90/spl deg/ phase-shift networks yields the reactive power associated with each wavelet frequency level or subband. The distortion power at each wavelet subband is then derived from the real, reactive and apparent powers of the subband, where the apparent power is the product of the v, i element pairs subband rms voltage and current. The advantage of viewing the real and reactive powers. In the wavelet domain is that the domain preserves both the frequency and time relationship of these powers. In addition, the reactive power associated with each wavelet subband is a signed quantity and thus has a direction associated with it. This permits tracking the reactive power flow in each subband through the power system.

Detecting motor bearing faults

Three-phase induction motors are the workhorses of industry because of their widespread use. They are used extensively for heating, cooling, refrigeration, pumping, conveyors, and similar applications. They offer users simple, rugged construction, easy maintenance, and cost-effective pricing. These factors have promoted standardization and development of a manufacturing infrastructure that has led to a vast installed base of motors; more than 90% of all motors used in industry worldwide are ac induction motors. Causes of motor failures are bearing faults, insulation faults, and rotor faults. Early detection of bearing faults allows replacement of the bearings, rather than replacement of the motor. The same type of bearing defects that plague such larger machines as 100 hp are mirrored in lower hp machines which has the same type of bearings. Even though the replacement of defective bearings is the cheapest fix among the three causes of failure, it is the most difficult one to detect. Motors that are in continuous use cannot be stopped for analysis. We have developed a circuit monitor for these motors. Incipient bearing failures are detectable by the presence of characteristic machine vibration frequencies associated with the various modes of bearing failure. We will show that circuit monitors that we developed can detect these frequencies using wavelet packet decomposition and a radial basis neural network. This device monitors an induction motors current and defines a bearing failure.

Motor bearing damage detection via wavelet analysis of the starting current transient

Preventive maintenance of induction motors plays an important role in avoiding expensive shut-downs due to motor failures. Motor Current Signature Analysis, MCSA, provides a non-intrusive way to assess the health of a machine. In this paper, the starting current transient of an induction motor is analyzed via discrete wavelet transform to detect bearing faults. The frequency subbands for bearing pre-fault and post-fault conditions are compared to identify the effects of bearing/machine resonant frequencies as the motor starts.

Harmonic analysis via wavelet packet decomposition using special elliptic half-band filters

The fast Fourier transform (FFT) is the most widely used power system harmonic analysis tool in real-time power metering due to its computational efficiency. Recently, an alternate method, i.e., wavelet packet decomposition (WPD), has been applied to power system signals to meter the voltage and current harmonics. Although the new method provides better analysis, the computational complexity of WPD places a limitation on its use in real-time metering. This paper proposes the use of all-pass-implemented special half-band elliptic infinite-impulse-response filters in the WPD of power system signals. The proposed implementation reduces the computational complexity to levels comparable to FFT.

Incandescent lamp flicker mitigation and measurement

Light flicker, a phenomenon of annoying light intensity variation, caused by fluctuating electrical loads, has been a major concern for both industrial and residential customers. This paper presents a novel Dynamic Phase Controller (DPC) for flicker mitigation by compensating for variations in the rms line voltage during each half-cycle. IEC61000-4-15 flickermeter standard is employed to assess the flicker reduction provided by this controller. A virtual IEC flickermeter is then developed to perform the flicker measurement, and it demonstrates that the controller is capable of efficient flicker mitigation.

Adjustable Speed Drive Bearing Fault Detection via Wavelet Packet Decomposition

Adjustable-speed drives perform many vital control functions in the industry, serving in such diverse applications as rolling mills, variable-speed compressors, fans, and pumps. When an adjustable-speed drive fails due to a bearing failure, it is usually catastrophic. Bearing defects introduce vibration anomalies that alter the current characteristic frequencies. This paper addresses the application of motor current signature analysis using wavelet packet decomposition to detect bearing faults in adjustable-speed drives.

Real-time Intranet controlled virtual instrument multiple-circuit power monitoring

The virtual instrument (VI) based power metering manifold (PMM), monitoring multiple branch circuits on a common distribution panel, is enhanced by the client-server interactive network architecture. The Intranet controlled power monitoring system integrates control, measurement and communication, while it still maintains economy by eliminating the extra network construction and hardware investment. Moreover, the multicast web application enables the power metering results to be accessed by multiple-user for variety applications in a real-time manner.

Universal serial bus enhances virtual instrument based distributed power monitoring

The universal serial bus (USB) links a distributed multicircuit power monitoring system to its virtual instrument (VI) host computer. The distributed interconnection provides enhanced system performance at reduced cost, since the USB host controller is a standard function of up-to-date personal computers (PCs) and low-cost high-performance USB hardware is readily available. The 12 Mb/s, recently updated to 480 Mb/s, transfer rate of the USB improves data transmission capability and boosts the real-time performance of the whole VI monitoring system when compared with conventional serial communications. In addition, the USB dynamic attachment and removal feature allows each meter to be connected or disconnected from its VI host computer without any system interruption. However, the complete VI solutions are not currently supported by any USB hosts and devices. This paper presents an innovative USB VI strategy to implement integrated power monitoring applications and shows its superior performance.