Use of the Motor As a Transducer to Monitor System Conditions

摘要

Motor current and power analysis methods have been developed to assist in the condition monitoring of a variety of motor-driven devices. The early work in this area was conducted at Oak Ridge National Laboratory (ORNL) on motor-operated valves in the mid-to-late 1980's in support of the U.S. Nuclear Regulatory Commission's Nuclear Plant Aging Research Program. The successful implementation of motor current signature analysis (MCSA) as a diagnostic for valves led to its application to other devices and to refinements in the methodologies used. In the last few years, work for the Nuclear Regulatory Commission and independent activities at ORNL and the Y-12 defense plant have resulted in additional, more thorough consideration of the merits of using motors as transducers for understanding system conditions. A variety of applications, ranging from fractional to over 1200 horsepower have been analyzed. Motor current and power analysis have been found to provide information that is complementary to that available from conventional diagnostics, such as vibration and pressure pulsation analysis. Inherent signal filtering associated with rotor to stator magnetic field coupling does limit the high frequency response capability of the motor as a transducer; as a result, certain phenomena, such as pump or fan vane pass energy, is not readily apparent in the motor electrical signals. On the other hand, the motor-monitored parameters have often been found to be much more sensitive than vibration transducers in detecting the effects of unsteady process conditions resulting from both system and process specific sources.