Motor Protection Research Articles

Determination of heat circumstances in the motor protection switch considering air flow

This paper presents the determination of heat conditions in the motor protection switch, with consideration to the air flow inside the switch. The finite-element method (FEM) was used for the calculation of the temperature conditions. Because of the temperature-dependent material properties and the geometrical peculiarities of the model, a sequential procedure for the calculation of the heat circumstances was developed. The specificity of the model is that the inside air is separated into two domains. These two domains are physically completely separated, but they have an indirect influence on each other through the thermal conductivity of partition walls

Differential expression of genes in amyotrophic lateral sclerosis revealed by profiling the post mortem cortex

The possible causes of ALS are unknown and multiple biological systems have been implicated. The goal of this study was to use gene expression profiling to evaluate a broad spectrum of systems in ALS. For this study, the medial lip of the human motor cortex and adjacent sensory cortex were collected at autopsy from five ALS patients and three normal individuals. Quantitative filter analysis revealed differential expression of mRNAs normalized to internal standards. A significant difference in expression of 275 genes was found in the ALS motor cortex; of the genes whose expression was changed, 10 were up-regulated and 265 were down-regulated. Six of the up-regulated genes were associated with cell surface activity and two were glutamate receptors; the latter is potentially consistent with the idea of excitotoxicity contributing to neurodegeneration in ALS. Of the down-regulated genes, the largest number were associated with transcription followed by those involved in antioxidant systems, inflammation, regulation of motor neuron function, lipid metabolism, protease inhibition, and protection against apoptosis including vascular endothelial growth factor. There were no significant differences in gene expression patterns between the sensory and motor cortex in the ALS brains. A total of 10% of the genes identified by microarray were chosen from each of the gene groups for validation by quantitative real time PCR (QRT-PCR). In order to increase the reliability of our gene array data, newly acquired motor and sensory cortex of ALS and control cases (n = 4 each) were used for validation. Of these, 86.4% changed in the same direction as determined in the microarrays. The gene profile data reported here are consistent with evidence that the ALS brain is characterized by an environment that is permissive for apoptosis, excitotoxicity and abnormal ubiquitination. This gene array study also suggested that a metal imbalance particularly for zinc could exist in ALS. Finally, given the amount of cellular stress that is thought to be part of the pathogenesis in ALS, there was a notable lack of increase in genes required to mount a protective response. This latter observation provides a conceptual framework in which to consider the possibility that ALS could result from a failure to mount adequate protective responses to physiological insults that, left unchecked, could progress to neurodegeneration.

Steady and transient states thermal analysis of induction machine at blocked rotor operation

The main limiting factor, among others, on how long an electrical machine can be operated continuously on load remains the temperature of the various circuit elements (electrical and magnetic) that constitute the machine. On the other hand, the maximum permissible temperature of the machine parts becomes imperative at blocked rotor operation and forms the key element for motor protection and condition monitoring. In this paper, a thermal network model is developed and used to predict the temperatures of the machine parts of a 7.5 kW induction machine at blocked rotor operation. The analysis of the proposed thermal network and the experimental results are presented and discussed. Comparison between the predicted steady state and transient state temperature rises of the test machine parts compare favourably with the experimental results at blocked rotor condition. Copyright © 2005 John Wiley & Sons, Ltd.

Assessing the Effects of Induction Rotor Transient Heating on Shaft Interference Fit During Force-Stopped Condition

This article investigates the design and finite element analysis of minimum interference fit between the shaft and motor rotor, against force-stop condition, to avoid slip at the interface during transient heating of the rotor. This condition occurs when the shaft is locked from rotation and the rotor is subject to the current induced by locked rotor for a certain period of time. Precise assessment of this time period is crucial for the protection of the induction motors, so that protective circuits can be designed to interrupt the current before this time is reached to avoid a spun shaft. The close to reality representative finite element analysis of such a system can offer many advantages during the design phase by eliminating the need for actual experiments, thus reducing both design cost and time. In this article, such a representative model is built and the required design requirements are demonstrated on the example induction motor rotor for two different interface fit values with friction.

High Frequency Attenuating Cable for Protection of Low-Voltage AC Motors Fed by PWM Inverters

Variable or adjustable speed drives generate pulse width modulated waveforms with risetimes below 100 ns. These very rapid transitions can cause large turn-to-turn voltages in inductive devices such as random wound motors, resulting in partial discharge and premature failure. One way to mitigate this problem is to absorb high frequency energy in the cable between the drive electronics and the motor. This contribution analyses design considerations for optimization of such a cable.

On line protection systems for induction motors

Protection of induction motors is very important since they are widely used in industry for many applications due to their high robustness, reliability, low cost and maintenance, high efficiency and long service life. So, protecting these motors is crucial for operations. This paper presents a combined protection approach for induction motors. To achieve this, the electrical values of the induction motor were measured with sensitivity ±1% through a data acquisition card and processed with software developed in Visual C++. An on line protection system for induction motors was achieved easily and effectively. The experimental results have shown that the induction motor was protected against the possible problems faced during the operation. The software developed for this protection provides flexible and reliable media for operators and their motors. It is expected that the motor protection achieved in this study might be faster than the classical techniques and also may be applied to larger motors easily after small modifications of the software.

Development of an educational computer program for the selection of cable and motor protection elements in hazardous atmospheres

This paper summarises comprehensively how to select and calibrate the electrical protection systems installed in a hazardous area environment, a coal mining installation, and presents the way to use widely available programming tools, such as MS Excel, to improve and speed-up this selection process.

Trends in Advanced Motor Protection and Monitoring

Industrial manufacturers strive to maximize uptime of plant operations and processes. However, downtime can be a valuable asset and present many opportunities to address those critical maintenance items that can impact reliability. Since motors and associated driven equipment comprise almost 90 percent of the process loads, identifying and correcting these mechanical and electrical maintenance problems will reduce unplanned production shutdowns and significantly increase business profits. This paper explores the various protection technologies available to the plant and design engineer for implementation of a cost effective and reliability centered motor management program.

Reignition Surge Effect in a Vacuum Circuit Breaker on Induction Motor Using the PSCAD/EMTDC

When switching off an induction motor by Vacuum Circuit Breaker, it would damage the motor insulation by switching re ignition surges. In order to investigate switching surge effects on motor insulation the simulations as parameters of cable length, motor size, with/without arrester around the Vacuum Circuit Breaker are performed by a Vacuum Circuit Breaker model that was developed by authors using the PSCAD/EMTDC. And the switching reignition surge profiles are obtained. Based on the surge profiles, the proper locations of the surge arrester for the protection of induction motor in distribution system are proposed. The results would be useful to analysis the re ignition surges effects and to select adequately the location of arrester in the distribution system.

What stator current processing-based technique to use for induction motor rotor faults diagnosis?

In recent years, marked improvement has been achieved in the design and manufacture of stator winding. However, motors driven by solid-state inverters undergo severe voltage stresses due to rapid switch-on and switch-off of semiconductor switches. Also, induction motors are required to operate in highly corrosive and dusty environments. Requirements such as these have spurred the development of vastly improved insulation material and treatment processes. But cage rotor design has undergone little change. As a result, rotor failures now account for a larger percentage of total induction motor failures. Broken cage bars and bearing deterioration are now the main cause of rotor failures. Moreover, with advances in digital technology over the last years, adequate data processing capability is now available on cost-effective hardware platforms, to monitor motors for a variety of abnormalities on a real time basis in addition to the normal motor protection functions. Such multifunction monitors are now starting to displace the multiplicity of electromechanical devices commonly applied for many years. For such reasons, this paper is devoted to a comparison of signal processing-based techniques for the detection of broken bars and bearing deterioration in induction motors. Features of these techniques which are relevant to fault detection are presented. These features are then analyzed and compared to deduce the most appropriate technique for induction motor rotor fault detection.

Formation of self‐excited vibrations in wet rotor motors and their influence on the motor current

AbstractResearch on condition monitoring for sensitive or process relevant drives has gained increasing importance in the latest past. The efforts made to reduce repairing costs and downtime led to the requirement of monitoring electrical drives. When doing so an important aspect is the detection of damages in an early state. Condition monitoring can be done by using various kinds of sensors and by analyzing stationary and non‐stationary signals. In some cases the use of vibration sensors for pump and motor protection and condition monitoring is difficult due to insufficient space and difficult environmental conditions, e.g. high water pressure. Submersible motor pumps for example are commonly working in deep wells down to 1000 meters. That is why motor current analysis remains as the only reliable monitoring method for condition monitoring and damage protection of submersible motor pumps. As one of the results of a highly interdisciplinary project this paper reports how the damage of the journal bearings of a wet rotor motor can be detected by motor current analysis. The investigations are bound on experimental measurements of two different types of centrifugal pumps with wet rotor motors.

What Stator Current Processing Based Technique to Use for Induction Motor Rotor Faults Diagnosis

In recent years, marked improvement has been achieved in the design and manufacture of stator winding. However, motors driven by solid-state inverters undergo severe voltage stresses due to rapid switch-on and switch-off of semiconductor switches. Also, induction motors are required to operate in highly corrosive and dusty environments. Requirements such as these have spurred the development of vastly improved insulation material and treatment processes. But cage rotor design has undergone little change. As a result, rotor failures now account for a larger percentage of total induction motor failures. Broken cage bars and bearing deterioration are now the main cause of rotor failures. Moreover, with advances in digital technology over the last years, adequate data processing capability is now available on cost-effective hardware platforms, to monitor motors for a variety of abnormalities on a real time basis in addition to the normal motor protection functions. Such multifunction monitors are now starting to displace the multiplicity of electromechanical devices commonly applied for many years. For such reasons, this paper is devoted to a comparison of signal processing-based techniques for the detection of broken bars and bearing deterioration in induction motors. Features of these techniques which are relevant to fault detection are presented. These features are then analyzed and compared to deduce the most appropriate technique for induction motor rotor fault detection.

Behavior of Induction Motor Protection Due to Voltage Sags and Short Interruptions

An experimental study and some calculations on induction motor behavior were carried out. The effects due to short interruptions and voltage sags were investigated. A standard three-phase squirrel-cage motor of 5.5 kW, 1500 rpm, 380 V was used. The presence of induction motor changes the voltage sag waveform and duration. Protection characteristic curves and contactor ride-through capability together with their improvement are also studied. The interaction between motor load, system hot-load pickup, and voltage sag magnitude determine the motor reacceleration duration and magnitudes. Besides, on-sag and post-sag currents can reach levels higher than the direct start values. Post-sag overcurrent duration can last more than twice the normal start time period, having specific energies in the same order of magnitude.

Differential expression of 14 genes in amyotrophic lateral sclerosis spinal cord detected using gridded cDNA arrays.

In order to obtain insight into the aetiology and pathogenesis of amyotrophic lateral sclerosis (ALS), high-density gene discovery arrays (GDA human version 1.2) containing 18 400 non-redundant EST cDNAs pooled from different tissue libraries have been used to monitor gene expression in lumbar spinal cord from ALS cases compared with controls. Quantitative filter analysis revealed differential expression of cDNAs normalized to internal standards. These candidates have been further investigated and their expression in spinal cord characterized in a panel of ALS and control subjects. Significant differential expression was obtained for 14 genes, 13 being elevated (up to six-fold) and one decreased (by 80%) in ALS. Amongst those elevated in ALS were thioredoxin and glial fibrilary acid protein, which have already been shown to be up-regulated in ALS, thus supporting the reliability of this approach. The other differentially regulated transcripts confirmed in the expression studies represent potential candidates in ALS pathogenesis being involved in antioxidant systems, neuroinflammation, the regulation of motor neurone function, lipid metabolism, protease inhibition and protection against apoptosis. The use of the GDA system has greatly facilitated the screening and retrieval of sequence information and has generated useful information on the cascade of molecular events occurring in ALS and potentially may highlight new candidates playing a role in the aetiology and progression of this disease.

Differential expression of 14 genes in amyotrophic lateral sclerosis spinal cord detected using gridded cDNA arrays

In order to obtain insight into the aetiology and pathogenesis of amyotrophic lateral sclerosis (ALS), high‐density gene discovery arrays (GDA human version 1.2) containing 18 400 non‐redundant EST cDNAs pooled from different tissue libraries have been used to monitor gene expression in lumbar spinal cord from ALS cases compared with controls. Quantitative filter analysis revealed differential expression of cDNAs normalized to internal standards. These candidates have been further investigated and their expression in spinal cord characterized in a panel of ALS and control subjects. Significant differential expression was obtained for 14 genes, 13 being elevated (up to six‐fold) and one decreased (by 80%) in ALS. Amongst those elevated in ALS were thioredoxin and glial fibrilary acid protein, which have already been shown to be up‐regulated in ALS, thus supporting the reliability of this approach. The other differentially regulated transcripts confirmed in the expression studies represent potential candidates in ALS pathogenesis being involved in antioxidant systems, neuroinflammation, the regulation of motor neurone function, lipid metabolism, protease inhibition and protection against apoptosis. The use of the GDA system has greatly facilitated the screening and retrieval of sequence information and has generated useful information on the cascade of molecular events occurring in ALS and potentially may highlight new candidates playing a role in the aetiology and progression of this disease.

A Switchboard Torque Indicator for AC Motors

The technique of calculating the air gap torque of an induction motor utilizing only the terminal voltages and currents has been known for some time; however implementation of this technique in a commercial instrument that must compete in accuracy with electromechanical instruments raises a number of issues that must be resolved. Because the derivation of the theorem relies on assumptions of symmetry in the motor, questions have been raised as to its accuracy in real machines. Also, the effects of saturation and core losses usually are ignored but are always present, especially in '' commodity''-type motors. There also are issues associated with the way data are processed, especially in the presence of strong harmonics. Finally, there is the question of how the system can be put into the field using only the information available to the user on the motor name plate. To clarify these issues, an experiment was set up using a PC equipped with standard A/D boards and a common 3/4 HP induction motor. The algorithm was implemented in C code on the PC. Upon the conclusion of these tests, the code was ported to a switchboard instrument and tested using a 15 HP motor. Results in both platforms were good, and the switchboard implementation has been adopted into the standard motor protection relay product.

TGFβ Trophic Factors Differentially Modulate Motor Axon Outgrowth and Protection from Excitotoxicity

Transforming growth factor (TGF) β-like trophic factors have been shown to be protective in acute neuronal injury paradigms. In the current study, we analyzed and compared members of this growing family, including glial cell line-derived neurotrophic factor (GDNF), neurturin, nodal, persephin, and TGFβ1, for protection against chronic glutamate toxicity. In parallel, we developed a organotypic spinal cord culture system to study the ability of these factors to promote motor axon outgrowth across white matter. Using these systems, we were able to differentiate the neuroprotective effect of the TGFβ-like factors from their motor axon outgrowth-promoting activity. GDNF, neurturin, persephin, nodal, and TGFβ1 all protected against excitotoxic motor neuron degeneration. Low amounts of GDNF (1 ng/ml) and high concentrations of neurturin induced vigorous motor axon outgrowth. In contrast, nodal, persephin, and TGFβ1 did not induce motor axon outgrowth. Both GDNF and neurturin bind to Ret receptor complexes and were capable of activating the MAP kinase pathway. A specific inhibitor of MAP kinase kinase, PD98059, inhibited the motor axon outgrowth-promoting activity of the GDNF but not the neuroprotective activity. Similarly, the specific PI3K inhibitors, LY294002 and wortmannin, were able to inhibit the promotion of motor axon outgrowth by GDNF, but did not affect neuroprotective activity. Our results suggest that the neurite outgrowth-promoting effect of GDNF is mediated through the PI3K and MAP kinase pathways. The neuroprotective effect of GDNF appears to be through a separate pathway.

"Right sizing" circuit breakers in motor starters

Instantaneous-trip, molded-case circuit breakers (MCCBs) have been applied successfully for low-voltage motor protection for many years. However, the changes in motor-starting characteristics have created more difficult challenges for the application engineer. The major challenge is successfully starting the low-voltage motor without causing the instantaneous-trip breaker to falsely trip without exceeding equipment ratings or violating limitations in the National Electrical Code (NEC). "Right sizing" circuit breakers for use in low-voltage combination motor starters is critical to the successful, reliable operation of plant and process facilities. If not properly applied, false tripping on motor starting and contact welding of contactors may occur. Moreover, changes in the NEC and improved motor efficiencies have impacted equipment selection and protection. The following information is intended to guide application engineers in their selection of the right breaker and its setting for more reliable motor protection: combination motor-starter components, circuit breaker characteristics, circuit breaker and combination. starter testing, motor starting characteristics, and component selection using coordination examples. The examples show how selecting the right breaker and breaker setting can avoid false tripping during starting, mitigate contact welding, and provide backup protection for overload conditions.

Asynchronous motor protection against dynamic instabilities

Asynchronous motor protection against dynamic instabilities

Use of LV and HV communicating protection relays on offshore platforms

The past ten years have seen a large growth in the use of communication protection relays in LV and HV switchgear on offshore platforms. They are used to simplify the interface between the process control system, which is part of the control monitoring and safety system, and the switchgear. The primary objective is to reduce overall costs by reducing cable and racking requirements, with the additional benefits of enhanced motor protection and monitoring, and greater flexibility during the design phase. This article looks at some of the recent offshore projects incorporating these relays and reviews the benefits and shortcomings of their design and implementation.