A magnetic actuator as excitation source in rotative systems is proposed, in order to accomplish modal analysis without contact between the actuator and the rotor. Although the use of electromagnets for applying forces to rotating machinery have been carried out with high performance level (for example, magnetic bearings), the development of a conveniently easy and cheap device for laboratory application presents interesting contribution to experimental methods used in test rigs based on similarity design to rotating machinery. The initial concept of the magnetic actuator proposed here is simple, but enables either the external excitation without contact or the vibration control when associated with a controller system. However, the calibrations of performance characteristics to attend the dynamic demand of the system in not so trivial. Following this focus, the paper brings practical experience and discussion about the development, calibration and performance analysis of a magnetic actuator used for rotating machinery tests. The influence of the electrical current in the actuator coils, the air-gap between actuator and rotative system, the type of surface of the actuator poles (flat or curved) as well as excitation frequency was experimentally verified and compared with theoretical concepts. Force estimation was carried out and compared with the measured force. The estimation was based on the magnetic flux density, measured by hall sensors, or input current and initial air-gap.
excitation without contact; rotordynamics; magnetic actuator
