Rotating magnetic field based instantaneous angular speed measurement of low speed rotating machines

Abstract

For early fault detection and health monitoring of low speed machines the instantaneous angular speed (IAS) measurement with high resolution and accuracy is required. The results show that IAS measurement is much more superior to the conventional methods i.e. analyzing acoustic waveforms, temperature variations, and vibrations etc. However accurate IAS measurement becomes very difficult due to slow and noisy response of the rotary transducers for low speed rotating machines. In the proposed technique, a fast rotating magnetic field (RMF) is used to measure the IAS for low-speed machines. An independent ac source is used to generate a balanced threephase ac voltage, which is applied to the stator windings of a synchro whose rotor is coupled with the rotating member or rotor of a motor. The RMF in the air gap generates emf in the rotor of synchro whose frequency depends upon the slip speed. Since the RMF revolves at a speed, several times the speed of the rotating member or the rotor of motor, hence the IAS measurement becomes very fast and accurate. The proposed scheme is tested successfully for instantaneous change of speed within a range of 0 to 2 rpm.

Technique for optimal placement of transducers for fault detection in rotating machines

“…15 A synchro and a fast rotating magnetic field (RMF)-based technique has been developed for the measurement of machine vibrations for machine condition monitoring, 16 which is further used to measure the instantaneous angular speed for low-speed machines. 17 Further advancements include shaped transducers that have been used to reduce the sensitivity of sensor output in structural health monitoring, which entails that the response can be made sensitive to particular regions of interest. 18 In addition, a monitoring system has been proposed to warn the operator of impending problems in the machining process and allows to alter and shutting down of the machining process to preserve the machine components.…”

Instantaneous Rotational Speed Measurement of Wind Turbine Blades using a Marker-Tracking Method

“…The rotational speed of each blade can be derived based on the rotation angle (θ 𝑖 ). The final rotational speed N is the average of individual speeds and is represented as (2).…”

“…As a result, mechanical tachometers require regular monitoring and maintenance. For this reason, several non-contact tachometers were invented, such as magnetic sensors [2], [3], which can be used to encode a rotating machine's angular position and rotational speed without contact, wear and tear. Another way of measuring rotational speed using electrostatic sensors is proposed in recent years [4], [5].…”

Enhancement of stability margin based on dynamic brake strategy

“…c) The depression in the electrical output power and machine terminal voltage is used to decide insertion of the brake. [15] d) The disturbance velocity in conjunction with angular to decide insertion of braking resistance. [16].…”

“…Removal strategies used by previous authors might be summarized as pursues: a) Angular velocity of the faulted machine can be used as a guide to decide removal of the brake. [15]. b) An optimum value for injection duration which gives the maximum possible reduction in the rotor swing amplitudes.…”