Non Invasive Sensors for Monitoring the Efficiency of AC Electrical Rotating Machines

Abstract

This paper presents a non invasive method for estimating the energy efficiency of induction motors used in industrial applications. This method is innovative because it is only based on the measurement of the external field emitted by the motor. The paper describes the sensors used, how they should be placed around the machine in order to decouple the external field components generated by both the air gap flux and the winding end-windings. The study emphasizes the influence of the eddy currents flowing in the yoke frame on the sensor position. A method to estimate the torque from the external field use is proposed. The measurements are transmitted by a wireless module (Zig-Bee) and they are centralized and stored on a PC computer.

Effects of external yoke and clamping-plates on AC motor external field

“…Indeed, as it is made of one piece, contrary to the laminated stator magnetic circuit, eddy currents flow in the yoke, creating a magnetic field, which the effects are opposed to the main field. As a consequence, the authors show in [6] that the magnetic field is only attenuated when it crosses the stator magnetic circuit whereas it is attenuated and also shifted when it crosses the external yoke. Fig.…”

“…The total external magnetic field has three components: a b NOR normal component, a b TAN tangential component and a b Z component, as shown in Fig. 1 [6]. In the paper, all the values concern the fundamental components.…”

“…The external field is generally measured with sensors placed close to the external housing, near the end-windings or at the middle of the stator magnetic circuit. The idea proposed by Zidat et al [6] is to analyse the external flux in order to determine an image of the air-gap flux density. This way, it is possible to determine experimentally some parameters of the machine, as the stator and rotor leakage inductances, which occur in the single-phase equivalent circuit of the induction machines [7].…”

“…This way, it is possible to determine experimentally some parameters of the machine, as the stator and rotor leakage inductances, which occur in the single-phase equivalent circuit of the induction machines [7]. The external flux measurement can also make it possible to estimate the machine efficiency [6] or information on the machine operating, like the electromagnetic torque. Nowadays the energy consumption of electric drives is at the heart of many research programs; these non-invasive tools are quite attractive.…”

Design of early fault detection technique for electrical assets using infrared thermograms

“…The parameters taken in this table are: type of monitoring system (invasive or non-invasive) [26,40,41]; speed of operation; accuracy [39]; human factor such as fatigue, vision level, and overlook of parameters; environmental factor [33] such as humidity, dust, extreme coldness or hotness, and rain; maintenance; running cost which includes repairing of the system, replacement of faulty and damaged part due to incessant operation; flexibility of use in variety of applications; direct effect on systems during fault, and reliability [33,[42][43][44]. The speed of operation and accuracy of the systems depends upon the processor speed, type of cabling system, distance of camera from the host terminal, type of protocol, and medium of data transfer.…”