Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Reexamination Certificate
1999-12-17
2001-07-17
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
C388S909000
Reexamination Certificate
active
06262550
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the monitoring and diagnosis of electrical motors, especially motors monitored by sensors located both at the motor and remotely at a circuit breaker or other remote motor control unit.
In one embodiment, the invention is a novel motor “fingerprinting” system that monitors and simultaneously tracks several dynamic and static motor conditions on site at the motor and from a remote motor control center. The data on the static and dynamic motor conditions is synchronized and stored in databases maintained at the motor, the motor control center and/or a central and/or local location. The invention may further include a novel method for determining the torque output of a motor based on the data collected from the motor.
Industrial electrical motors are in widespread use in manufacturing, power generation and other industrial facilities. These motors must be monitored and maintained to ensure their proper operation. There are a wide variety of motor parameters that can be monitored to provide service personnel with information regarding the condition of a motor. These parameters include dynamic operating conditions, such as vibration, speed, temperature, and stray magnetic flux that are measured by sensors on or adjacent the motor. Other dynamic motor parameters, such as voltage and current, are best monitored at remote stations, such as at transformers and circuit breakers where those parameters can be safely monitored by avoiding the high voltage and current levels that may exist directly at the motor. In addition, static motor conditions, such as current leakage through insulation, are measured when the motor is off-line, e.g., disconnected from its power supply.
In the past, static and dynamic motor parameters have not been monitored by an integrated sensor and instrumentation system. Similarly, the data on motor condition has not been collected simultaneously in real-time to allow for review of motor condition data, or to allow for storage of data on various motor parameters in a comprehensive database. Instead of having a synchronized collection of the current and historical data on the condition of a motor, service personnel have had to rely on many independent test instruments and databases to obtain static and dynamic motor data. These independent tests do not collect data synchronously and do not allow service personnel to synchronize data from various test instruments. In addition, the coordinated analysis of certain system events, i.e. contact closures, in conjunction with motor parameters has been difficult if not impossible to achieve. Thus, service personnel are not able to compare the timing of certain test results, such as current and voltage inputs of a motor, with the timing of other test results, such as vibration, stray magnetic flux and motor temperature or system events (i.e., contact closures, valve functions, etc). Other disadvantages of using independent instruments include the inconvenience to service personnel and that service personnel do not have ready access to complete and coordinated motor data when diagnosing motor problems. The motor service personnel have a long-felt need for access to aggregate collections of data on a motor to allow them to better detect when motors require servicing, repairs, or replacement, as well as to assess the suitability of a motor for a certain function or location.
Prior motor test equipment provided limited functional test capability. These prior test instruments were usually individual instruments that addressed a specific motor characteristic or condition. The instruments were also often limited to use with a certain class of motors, such as low voltage, medium voltage, alternating current (AC) induction, AC synchronous, direct current (DC) and other motor classes. A service person had to operate and interpret many different motor test instruments to service motors of different classes. He had to be trained and be knowledgeable of all of the instrument types. The service person also had to have access to each of these instruments, and know where the instruments were positioned with respect to the motor in order to gather the motor data from the instruments.
BRIEF SUMMARY OF THE INVENTION
There is a long-felt need to synchronously collect motor data from the various sensors and test instruments that monitor a motor on-site and remotely at a motor control center (MCC).
Briefly, according to one embodiment, a motor monitoring systemcomprises: an on-site motor instrument unit having an on-site motor sensor (including at least one sensing device) for monitoring a motor, wherein the on-site sensor generates a signal representative of a first motor condition; an on-site motor computer unitelectronically connectable to the on-site motor measurement unit, and processing the signal representative of the first motor condition; an off-site motor control center having a remote sensor (including at least one sensing device) for remotely monitoring a second motor condition, wherein the remote sensor generates a signal representative of a second motor condition; an off-site motor control center computer unit electronically connectable to the off-site motor control center and processing the signals representative of the second motor condition, and a communications link between the on-site motor computer unit and the off-site computer.
Data on the dynamic and static operating conditions of a motor provide much information as to whether and when the motor requires maintenance. Motor service companies employ a technique of condition based monitoring (CBM) to maintain industrial motors. Presently, CBM is done with a number of independent dynamic and static measurements to predict when and what motor maintenance is needed. Exemplary, inputs of motor data include current, voltage, leakage current, leakage flux, temperature, vibration, shaft position, speed, RF activity and other characteristics some of which are measured while the motor is operating (hereinafter referred to collectively as dynamic tests). Other tests are measured when the motor is disconnected from its power source, and include static tests such as insulation leakage, megger, and symmetry.
Capturing static and synchronized dynamic motor data from on-site and remote locations and storage of this data in a comprehensive database provides time correlated “fingerprint” of the motor, the load on the motor, and the motor's operation. In addition, displaying historical operational data of a motor would show to maintenance personnel the trends in operating parameters that would help predict motor operation and greatly enhance plant service maintenance.
A novel motor monitoring system has been developed to create an integrated “fingerprint” of a motor. A motor “fingerprint” is a collection of magnitudes, signatures, waveforms, system responses, parameters, text etc. in a database describing the conditional state of a motor. The motor fingerprint incorporates the available motor data necessary to characterize the condition of the motor and the process it is driving.
The Motor Monitoring System captures static (off-line) motor parameters, and dynamic motor parameters at the motor site and at a motor control center. The motor control center is usually remote from the motor, and may be located at, for example, a circuit breaker cabinet or a step-down transformer powering the motor. The motor monitoring system also correlates process events with dynamic motor data to provide a “real-time” window into the motor's dynamic load(s) and their operating status. A complete collection of synchronized motor data may be stored in a comprehensive database maintained locally at the Motor Unit associated with the motor, remotely at the MCC Unit associated with the motor control center, at a satellite database location or at a central database location.
The Motor Monitoring System is an integrated system that acquires time-coordinated data on available motor parameters for processing and storage to a database. Monitoring units a
Kliman Gerald B.
Koegl Rudolph A.
Krahn John R.
Premerlani William J.
General Electric Company
Leykin Rita
Nappi Robert E.
Nixon & Vanderhye P.C.
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