Hall Effect Current Transducers Research Articles

Condition Monitoring of Electrolytic Capacitors in Boost Converters by Magnetic Sensors

The aluminum electrolytic capacitors (AEC) are important in filtering and energy storage applications since they are of high energy density and low cost. However, the AECs suffer from low reliability and limited lifetime due to the electrolyte vaporization. The degradation of AECs challenges the reliability and efficiency of the power electronic systems. Therefore, it is essential to monitor the condition of AECs for system reliability and efficiency. In this paper, a real-time condition monitoring technique for input and output AECs based on the estimation of equivalent series resistance (ESR) was developed for the boost converter. The ESRs were estimated by using the capacitor and inductor current obtained through the magnetic-field sensing by magnetic sensors. The influences of the load, duty cycle, inductance, ESR, and capacitance on the ESR estimation were investigated to develop the proposed methodology. The proposed methodology can largely improve the accuracy of the estimated ESR of output AEC in the boost converter. The higher accuracy enables predictive maintenance of AECs and contributes to the reliability and efficiency of power electronic systems. The simulation and experimental results from −25 °C to 100 °C verified that the proposed methodology could be used to estimate the ESR of input and output AECs accurately. The experimental results showed that the compact tunnel magnetoresistance (TMR) sensors were capable of measuring the capacitor and inductor current for the estimation of ESR. This technique is cost-effective and non-invasive since it can be implemented with TMR magnetic sensors and does not require the Hall-effect current transducers with magnetic concentrators of larger volume, higher cost, and limited bandwidth or invasive shunt resistors.

Fault Diagnosis of Low-Power Three-Phase Induction Motor

Abstract An Induction motor reliability survey at an egg processing plant shows that almost 50% of the total motor failures are fan induction motors. Visual investigations of the faulty fan motors show that the main cause of the induction motor failure is air gap eccentricity. In this study, experimental tests are performed on a 1.1kW three-phase induction motor to detect air gap eccentricity and overheating of the induction motor. Heating tests show that end shield housing temperature reaches 100°C with blocked air flow from the fan, which can reduce the lifespan of the bearing. Dimension measurements of the end shield housing show that the dimensions of both tested motors back-end shields are larger than ISO tolerance grade limit. It leads to a loose fit between the housing and bearing, causing air gap eccentricity. Also, both motor back end shield housing has an out-of-round condition leading to an unbalanced magnetic pull. To detect the air gap eccentricity caused by too loose of a fit between housing bore and bearing, current Park’s vector approach is used. To measure three phase current, Hall Effect current transducers, a digital oscilloscope is used and Matlab software to process the measurement data. Results show that Park’s vector approach can be used to detect the air gap eccentricity caused by too loose a fit between bearing and housing. Therefore, the Park’s vector approach can be used to diagnose air gap eccentricity and analyse the type of the air gap eccentricity.

Experimental investigation on detection of air gap eccentricity in induction motors by current and vibration signature analysis using non-invasive sensors

The contents of this paper reports an experimental investigation carried out to detect the air gap eccentricity faults under varying load conditions using non-invasive transducers to monitor the current and vibration signals as a diagnostic medium. Experimental results of vibration signature analysis using Micro-Electro-Mechanical Systems (MEMS) accelerometer and Motor Current Signature Analysis (MCSA) using Hall Effect current transducers are compared and found nearly common signatures. Spectral analysis is carried out using decimation in time Fast Fourier Transform algorithm using FFT analyzer. This study also examines the usefulness of vibration signature analysis using MEMS to detect the eccentricity faults in developing a compact, miniaturized and cost effective instrument.

Improvement of Hall Effect Current Transducer Metrological Performances in the Presence of Harmonic Distortion

The performance of Hall effect current transducers (HECTs), under distorted waveform conditions, is usually characterized by means of a frequency response test. In this paper, it was investigated if frequency response is able to correctly evaluate the ratio and the phase errors under distorted conditions. Two HECTs, with the accuracy class level of 1% and 0.5%, respectively, were experimentally characterized under two conditions: 1) sinusoidal excitation with frequencies ranging from 50 to 750 Hz, which is the well-known frequency response test, and 2) nonsinusoidal excitation using fundamental frequency and one harmonic with adjusted amplitude and phase shift. It was found that ratio and phase errors are weakly affected by the harmonic amplitude and phase shift, with respect to the fundamental in the accuracy level of 0.1% and 0.05°. They have, instead, a strong dependence from conductor location in the HECT window. These results suggest that the frequency response approach for the evaluation of HECT performance, under distorted waveform conditions, can be used for an error compensation method only if the position of the primary conductor is known. An error compensation method, based on the frequency response, was implemented and tested with a distorted waveform composed of fundamental and many harmonics. For each of the harmonic components, the errors were reduced to one tenth of the measured ones.

Development of Current Sensor for Cutting Force Measurement in Turning

The importance of monitoring cutting forces in turning has been well recognized in machine tool communities. This paper proposes a new method to measure the cutting forces in turning using inexpensive current sensors and the cutting force model. First, the relationship between the various factors, which affect the performance of the spindle and feed drive systems, and the models of the spindle and feed drive systems are analyzed. Then, some reliable and inexpensive Hall-effect current transducers are employed to sense the current signals of the ac servomotor in a computer numeric control (CNC) turning center; the tangential (F/sub t/) and axial (F/sub a/) cutting forces in turning are estimated by applying a neuro-fuzzy technique. Finally, the normal cutting pressure (K/sub n/) and effective friction coefficient (K/sub f/) are calculated through the cutting mechanical model, so the axial cutting forces (F/sub r/) can also be estimated based on the model of cutting force. Experimental results demonstrate that the method proposed can measure tangential, axial, and radial cutting forces with an error of less than 10%, 5% and 25%, respectively.

A linearization method for commercial Hall-effect current transducers

The need for high-current transducers featuring wide-band and high-insulation levels is becoming a more and more impelling need in the electric power network, as the current distortion increases due to the proliferation of nonlinear, time-variant loads. The closed-loop Hall-effect current transducers show a good compromise between cost and metrological performance. On the other hand, they may introduce an unacceptable nonlinearity error when the dynamic range of the input current is a reduced portion of the dynamic range of the transducer and may show a large drift of their gain with temperature. The paper proposes a simple method for reduction of the nonlinearity error when the input signal is an unbiased sinewave and the automatic calibration of the gain. Experimental results are also reported, showing the method effectiveness.

MICROCONTROLLER BASED THREE-PHASE INDUCTION MOTOR PROTECTION RELAY WITH OPERATOR SELECTABLE THERMAL IT CURVE FEATURE

This paper presents a Microcontroller based three phase induction motor protection relay. The scheme employs the Hall effect current transducers for sensing motor line currents, and an ‘Auto ranging ’ feature, in order to acquire motor line currents accurately from no load to blocked rotor current. The flexibility of ‘Operator selectable thermal current versus time (I-T) curves feature’ is incorporated in the relay software, in which using the operator fed cold curve points and the thermal time constant of the motor, the corresponding I-T cold and hot curves can be fitted by the relay Software. The relay performance, with the selected I-T curves has been studied in the laboratory by testing on a three phase, 5 h.p. induction motor and it has been observed that the relay to follow the selected I-T characteristics.