Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1998-05-06
2001-10-02
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S679000, C340S683000, C361S023000, C318S490000
Reexamination Certificate
active
06297742
ABSTRACT:
The present invention relates generally to a machine monitor. More particularly, the present invention relates to a self-contained machine monitor which attaches to a mount proximate a machine to sense machine operating parameters, to determine machine status based on the sensed operating parameters, and to indicate either visually or aurally, or both, the status of the machine.
BACKGROUND
Electric motors, particularly ac induction motors, are employed in many industrial and manufacturing facilities. Among their many applications, ac induction motors are used to provide power to machinery in manufacturing facilities. Downtime caused by a failure of an electric motor reduces productivity and profitability. Electric motors, therefore, are important elements of industrial facilities and their health and condition must be closely observed to prevent motor failures that result in costly unscheduled downtime.
Evaluating the extent of stator wire insulation degradation has long been considered an effective way of determining the condition of an electric motor. As the motor ages, insulation breakdown occurs due to high motor temperature and other operating stresses. When insulation degradation reaches a critical point, the motor windings short circuit, thereby resulting in motor failure.
Attempts have been made in the art to provide electric motor monitoring systems capable of monitoring the condition of the motor. Many of these systems focus on determining the amount of insulation degradation as a way of predicting the remaining useful life of the motor. For example, in U.S. Pat. No. 5,019,760 to Chu et al., a system is disclosed for continuously determining the consumed life of electrical motor winding insulation. Insulation degradation is calculated as a function of insulation thermal properties, insulation temperature, and motor power rating. The temperature of the insulation is measured over a time interval, and the average winding temperature is used to calculate a consumed life of the insulation for that time interval. The consumed life values calculated for each time interval are then summed to determine a total consumed life of the motor.
In U.S. Pat. No. 5,189,350 to Mallett, there is described a monitoring system for an electric motor. A temperature sensor monitors the operating temperature of the motor. A memory is provided for storing the “absolute maximum operating temperature” and a “predetermined maximum permitted operating temperature” of the motor. An indicator is used for indicating the sensed motor temperature as lying within either a safe, hazardous, or dangerous range as determined by comparison of the sensed motor temperature to the stored maximums. A recorder stores the number of times the motor has operated beyond the predetermined maximum permitted operating temperature and the number of times the motor has operated beyond the absolute maximum operating temperature.
In U.S. Pat. No. 4,525,763 to Hardy et al., a system for predicting the remaining useful life of an electric motor is described. Hardy utilizes motor temperature and past history to determine the amount of insulation degradation, which forms the basis of the remaining useful life prediction. The predicted remaining useful life is displayed and may be used to issue a warning or to trip circuit breakers supplying power to the motor when projected life is shorter than predicted life.
While high motor temperature, and resultant insulation degradation can contribute to electric motor failures, it is not the only factor. There are many complex and interrelated operating characteristics of electric motors that affect the health and longevity of the motor. Factors such as motor speed, loading, vibration, and the number of motor starts/stops also affect motor life. However, all known electric motor monitors today are incapable of monitoring these operating characteristics in an efficient, productive manner.
Known prior art devices do not adequately address multiple contributing factors to motor failure, maintenance issues for an electric motor monitoring system itself, enhancing the useability of a monitoring system, or providing a monitoring system that can be applied in a cost effective manner.
What is needed, therefore, is an electric motor monitor capable of sensing and analyzing various stresses experienced by the motor during the life of the motor, including temperature, and storing these stress data as the operation history of the motor. The monitor should be configured to allow stored data to be easily downloaded for archival or further analysis. For purposes of maintainability and affordability, the monitor should be relatively small and self-contained with its own internal power source, and capable of being mounted directly to the motor. Finally, with the monitor mounted directly to the motor, it should be rugged and capable of withstanding the rigors of a harsh industrial environment.
SUMMARY
With regard to the foregoing and other objects, the invention provides a monitor for being placed in sensory contact with a machine for monitoring the operation of the machine and producing an operation history. The monitor includes a structural enclosure with an engagement surface. A fastener is used to attach the engagement surface to a mount proximate the machine so that the engagement surface is in sensory contact with the machine. A power supply supplies electrical power to the monitor. A sensor, such as a vibration transducer, is disposed in the enclosure to sense an operating parameter of the machine and to produce sensor signals representative of the operating parameter that was sensed. A signal processor is disposed in the enclosure to receive, process, and analyze the sensor signals to produce sensor data corresponding to the operating status of the machine. When analysis of the sensor signals indicates the existence of an anomalous machine condition, an alarm signal is produced. An indicator receives the alarm signal and produces a humanly perceivable indication of an anomalous machine operating condition. Memory is provided for storing operational programming for use by the processor and sensor data produced by the processor.
In a further aspect of the invention, the processor is operable to perform a fast Fourier transform of the sensor signals to produce machine operating data in the form of spectra. The processor then analyzes the spectra to determine machine condition.
In another aspect, the indicator is a visual indicator which provides machine operators with a visual indication corresponding to the operating condition of the machine based on the presence or absence of alarm signals. The severity of an anomalous condition can be indicated as well. Alternatively, the indicator may take the form of an aural indicator which produces an aural indication of the machine's operating condition.
The monitor may further include a communications module to enable the monitor to communicate with a peripheral device for data transfer and programming. For example, the communications module may be an infrared data port or an RF communications module.
The monitor may be attached in a variety of ways. For example, the fastener may include a threaded stud attached to the outer surface of the machine. A recess formed in the monitor enclosure is threaded to receive the stud so that when the recess and stud are adjacent one another, rotation of the monitor in a first direction attaches the monitor to the stud. To disengage the monitor from the machine, the monitor is rotated in an opposite direction. As another example, an adhesive may be used to attach the monitor to the outer surface of the machine.
The present invention also provides a machine fault detection and indicator system for monitoring the operating condition of a plurality of machines and indicating when one or more anomalous machine conditions are detected. For each machine being monitored, the system includes at least one monitor in sensory contact with the machine to sense and analyze an operating characteristic of the machine. When an alar
Canada Ronald G.
Pardue Eugene F.
Robinson James C.
CSI Technology, Inc.
Hofsass Jeffery
La Anh
Luedeka Neely & Graham P.C.
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