Motor Terminals Research Articles

Electrical Monitoring of Damper Bar Condition in Salient-Pole Synchronous Motors Without Motor Disassembly

The damper (or amortisseur) winding of synchronous motors (SMs) is a critical component required for starting the motor. Several cases of the forced outage of industrial processes due to the starting failure of salient-pole SMs caused by damper bar failure have recently been reported. The detection of broken damper bars is difficult since they are active only during rotor acceleration, and offline visual inspection is the only means of testing available in the field. It was recently shown that the broken damper bars can be detected from the airgap flux, but this requires the installation of airgap flux sensors inside the motor. In this article, a method based on the analysis of the stator starting current is proposed for detecting broken damper bars. In addition, an electrical detection method based on signal injection from the motor terminals is proposed. The new methods have been devised to provide remote testing from the motor control center without motor disassembly required in existing tests. Finite-element analysis (1 MW) and experimental testing (30 kW) performed on salient-pole SMs with emulated broken damper bars show that the proposed methods can provide the sensitive and reliable detection of damper bar failures.

A Simple Feedforward Approach to Stabilize VSI-Fed Induction Motor With Filter in RFOC

LC filters are used in between a pulsewidth modulated three-phase voltage source inverter and a squirrel cage induction motor (SQIM) to reduce the losses in the motor and the high dv/dt at the motor terminals by feeding the motor with three-phase sinusoidal voltages. However, it affects the rotor-flux oriented control (RFOC) of the SQIM drive because of the sustained resonant frequency oscillations. It also destabilizes the drive at some operating points if proper control action is not taken. This article proposes a simple feedforward (FF) technique where the FF terms are subtracted from the d- and q-axis stator-current references to damp out the resonant frequency oscillations. Additional sensors and controllers are not required except the sensors and controllers used in RFOC of SQIM without filter. It does not depend on the tedious calculation of damping gain like in any active damping method. The stability of the drive has been analyzed and verified through simulation as well as experimental results at different test conditions. It ensures good steady-state and dynamic performances of the SQIM with filter. There is no need to change the parameters of four proportional-integral controllers previously designed for the RFOC of SQIM without filter.

Air Flow Control of a Smart Electric Fan using IoT Solutions

Remote control of electric fans by the application of IoT technology addresses the restrictions of “push button” controls that are usual in conventional fans. This paper explains a new control method for air flow control of a Smart Electric Fan (SEF), in this case fans mainly used in the household. In this new method the supply voltage that is applied to the motor terminals of the SEF is precisely changed with the mobile application developed by using IoT solutions. As this proposed method integrates with the conventional control methods referred to as the Firing Angle Control method or Phase Angle Control method with a new IoT-based solution, the controlling of any device becomes simpler. We developed a mobile application that enables the fan to be remotely controlled using a smartphone or tablet computer. The phase or delay angle of the voltage waveform is changed by giving as an input from the smart phone mobile application, and this results in minimizing the power loss caused due to switching in case of push button system. We demonstrated that by using this app, implementing the IoT-based solution, the air flow rate of the SEF was increased and the performance of the SEF exceeded the air flow rate of the original, conventionally controlled fan with the speed of the fan being significantly increased. Applying this control method has thus been verified to be advantageous and appropriate for the remote control of the air flow and fan speed, resulting in the efficient Smart Electric Fan. The main focus of this research was to implement the integrated control method in the residential fans.

Cylindrical Cam Electromagnetic Vibration Damper Utilizing Negative Shunt Resistance

Two common problems in utilizing electromagnetic dampers are addressed in this article. The first problem is the maximum available damping that can be created in an electromagnetic actuator using a positive resistive load. Maximum damping is achieved when the motor terminals are placed in a short circuit configuration, but it might not be enough in certain applications. As a solution, a method to produce negative resistance using power electronics and control techniques is presented in this article. The negative resistance cancels part of the resistance of the electromagnetic machine, which leads to producing larger electrical current in the actuator coils. As a result, higher damping levels are generated. The other contribution of this article is devising an effective motion rectification mechanism for converting the translational motion into rotary motion that drives an electric machine. To this end, a cylindrical cam mechanism is proposed which can provide longer strokes while keeping the geometry and size of the damper similar to the axial dampers used in automotive and bicycle dampers. The mechanism shows longer values for the ratio of stroke to maximum length compared to other designs reported in the literature.

Analytical and Simulation Fair Comparison of Three Level Si IGBT Based NPC Topologies and Two Level SiC MOSFET Based Topology for High Speed Drives

Wide bandgap (WBG) power devices such as silicon carbide (SiC) can viably supply high speed electrical drives, due to their capability to increase efficiency and reduce the size of the power converters. On the other hand, high frequency operation of the SiC devices emphasizes the effect of parasitics, which generates reflected wave transient overvoltage on motor terminals, reducing the life time and the reliability of electric drives. In this paper, a SiC metal-oxide-semiconductor field-effect transistor (MOSFET) based two level (2L) inverter is systematically studied and compared to the performance of Si insulated-gate bipolar transistor (IGBT) based three level (3L) neutral point clamped (NPC) inverter topologies, for high speed AC motor loads, in terms of efficiency, overvoltages, heat sink design, and cost. A fair comparison was introduced for the first time, having the same output voltage capabilities, output current total harmonic distortion (THD), and overvoltages for the three systems. The analysis indicated the convenience of using the SiC MOSFET based 2L inverter for lower output power. In the case of the maximum output power, the heat sink volume was found to be 20% higher for the 2L SiC based inverter when compared to 3L NPC topologies. Simulations were carried out by realistic dynamic models of power switch modules obtained from the manufacturer’s experimental tests and verified both in the LTspice and PLECS simulation packages.

Target-wide Induction and Synapse Type-Specific Robustness of Presynaptic Homeostasis.

Presynaptic homeostatic plasticity (PHP) is an evolutionarily conserved form of adaptive neuromodulation and is observed at both central and peripheral synapses. In this work, we make several fundamental advances by interrogating the synapse specificity of PHP. We define how PHP remains robust to acute versus long-term neurotransmitter receptor perturbation. We describe a general PHP property that includes global induction and synapse-specific expression mechanisms. Finally, we detail a novel synapse-specific PHP expression mechanism that enables the conversion from short- to long-term PHP expression. If our data can be extended to other systems, including the mammalian central nervous system, they suggest that PHP can be broadly induced and expressed to sustain the function of complex neural circuitry.

Power Losses Distribution in SiC Inverter Based Electric Motor Drives

This article is an investigation on the analysis and performance of the passive soft-switching snubber inverter (PSSSI). The efficiency of the power cable and electric motor used in industrial electric drive applications is also taken into consideration. As reported in the literature, the PSSSI is used to reduce the overvoltage on the motor side when both voltage source inverters are equipped with high-speed semiconductor devices and a long power cable is used. The PSSSI configuration derives from the conventional two-level inverter by adding a diode–capacitor snubber for each switching power device. Furthermore, an additional circuit is used to recover energy from the snubber capacitors. The three-phase PSSSI is carefully designed taking into account several system parameters, such as the dV/dt , the length of the power cable between the motor and the inverter, the gate resistance of the switches, the dead-time, the snubber capacitors’ value, and the switching frequency. Experimental results show a good efficiency performance of the entire electric drive as well as a reduced dV/dt at the electric motor terminals when the PSSSI is used compared to when the two-level three-phase inverter is adopted.

An Induction Machine With Tapped Stator Windings for LCI-Fed Medium Voltage Drive Applications

The search for thyristor-based load commutated inverter (LCI) fed induction motor drives for medium voltage (MV) applications has been ongoing since the past few decades, and several new topologies have been proposed. Low cost, better efficiency, and greater ruggedness are the definite advantages of these drives. Since leading power factor is an absolute necessity for load commutation, most of these drives supply additional auxiliary reactive power at the motor terminals. However, in MV applications, this would require the auxiliary source of reactive power (typically a capacitor bank or voltage source inverter (VSI)), also to be rated for MV. To overcome this issue, a new topology using a tapped stator winding induction machine is proposed in this article. Here, a low voltage tapping on the stator winding is used to connect a low voltage VSI which supplies reactive power to the machine. The LCI is used to provide all the active power required from the main stator terminals rated for the MV operation. This article describes the proposed machine and drive configuration and the vector control method for the LCI fed drive. Experimental verification is done using a 75-kW, 3.3-kV prototype machine with a 350 V tapping on the stator winding.

Diffusive representation modelling thermal and overvoltage for permanent magnet synchronous motor fed by voltage inverter

Life of electric machines is very sensitive to temperature increases especially due to the fragility of their windings as well as to the overvoltage at the motor's terminals. Therefore, it is necessary to find the temperature in the most sensitive areas of the machine. It has been known for a long time that temperature rise is caused by the losses in the machine; thus, various models have been proposed. It has also been shown that the permanent magnet synchronous motor fed by a voltage inverter overheats more than the one supplied by a sinusoidal voltage. Indeed the permanent magnet synchronous motor fed by a voltage inverter deserves special attention. In this paper a new technique based on diffusive representation is used to develop two coupled mathematical models; one for thermal variation in some of the most delicate places of winding and another one for the overvoltage at the motor's terminals. The obtained simulations and experimental results show clearly the validity and the high performance of the proposed models.

Adaptive Fuzzy-Based IRFOC of Speed Sensorless Six-Phase Induction Motor Drive System

In recent times, instead of three-phase induction motors (IM), multi-phase motors have been used in several applications, due to numerous advantages that they offer. Elimination of mechanical position or speed sensors allures for adjustable speed drives of IM. It leads to cost reduction, lesser maintenance and increased reliability of the motor drive. To eliminate the speed sensor, the rotor speed is estimated from measured stator currents and voltages at motor terminals. This paper proposes a scheme based on speed estimation method using Model Reference Adaptive System (MRAS) in conjunction with Adaptive Fuzzy Knowledge Based Controller (AFKBC) to improve the performance of a sensorless Indirect Rotor Field Oriented Control (IRFOC) of six-phase IM drive. AFKBC allows to operate at various operating conditions. A fitness function is defined for Queen Bee-based Genetic Algorithm (QBGA) to tune the scaling factor of AFKBC which improves the transient and steady state performances. The performance of the proposed scheme is evaluated by simulation on Matlab/Simulink package. The results of the proposed scheme are compared with conventional PI-based speed controller of the drive system. The proposed controller scheme improves the performance of the drive system at various operating conditions. The estimated speed algorithm gives good correlation between estimated and actual motor speed. The simulation results also illustrate that proposed scheme is robust and suitable for high performances six-phase IM drive.

A Measurement-Based Wide-Frequency Model for Aircraft Wound-Rotor Synchronous Machine

For the safety of the wound-rotor synchronous machine (WRSM) in aircraft applications, the overvoltage at the motor terminals, electromagnetic interference (EMI) performance, and bearing currents as well as the loss analysis are the core areas to be addressed. The high-frequency (HF) modeling method of the WRSM, which has a strong relationship with all these core areas, is a very critical theme. In this paper, a measurement-based wide-frequency (WF) modeling method to characterize the impedance of the WRSM is proposed to build a straightforward correlation between fundamental models and HF parasitic circuit elements. In this paper, the voltage-behind-reactance method is applied to demonstrate the rotor-angle-dependent characters in the low-frequency domain, while the vector fitting method is used to parameterize the HF branch for high-accuracy consideration. By doing this, a WF electrical model with multistage RLC units is formed, which comprehensively considers both the saliency character of the machine and frequency range. The WF model is also compatible with the circuit-based simulation. Finally, the EMI prediction orientated simulation and experimental results are implemented on a 10 kVA WRSM prototype to verify the correctness and advantages of the proposed modeling method.

Signal Exchange through Extracellular Vesicles in Neuromuscular Junction Establishment and Maintenance: From Physiology to Pathology.

Neuromuscular junction (NMJ) formation involves morphological changes both in motor terminals and muscle membrane. The molecular mechanisms leading to NMJ formation and maintenance have not yet been fully elucidated. During the last decade, it has become clear that virtually all cells release different types of extracellular vesicles (EVs), which can be taken up by nearby or distant cells modulating their activity. Initially, EVs were associated to a mechanism involved in the elimination of unwanted material; subsequent evidence demonstrated that exosomes, and more in general EVs, play a key role in intercellular communication by transferring proteins, lipids, DNA and RNA to target cells. Recently, EVs have emerged as potent carriers for Wnt, bone morphogenetic protein, miRNA secretion and extracellular traveling. Convincing evidence demonstrates that presynaptic terminals release exosomes that are taken up by muscle cells, and these exosomes can modulate synaptic plasticity in the recipient muscle cell in vivo. Furthermore, recent data highlighted that EVs could also be a potential cause of neurodegenerative disorders. Indeed, mutant SOD1, TDP-43 and FUS/TLS can be secreted by neural cells packaged into EVs and enter in neighboring neural cells, contributing to the onset and severity of the disease.

A Voltage-Edge-Rate-Limiting Soft-Switching Inverter Based on Auxiliary Resonant Pole

To increase switching frequencies while limiting switching losses in voltage-source inverters, power switches have been made significantly faster with achievable switching times now less than 100 ns. However, faster switches generate larger inverter output voltage edge rates ( ${dv/dt} $ ) and result in deleterious effects in variable-speed drive systems including transient overvoltages at motor terminals, electromagnetic interference, and bearing failures due to microarcs. A common approach for limiting peak ${dv/dt} $ involves using a ${dv/dt} $ filter. However, the ${dv/dt} $ filter introduces extra power losses and increases the overall size and weight of the system. Soft-switching circuits, which were originally developed to reduce switching losses, can help reduce ${dv/dt} $ , but using soft-switching to accurately control ${dv/dt} $ has not been fully explored. In this paper, a new soft-switching circuit, entitled the auxiliary resonant soft-edge pole (ARSEP), is set forth. ARSEP improves the available soft-switching circuits so that ${dv/dt} $ can be accurately controlled through the circuit parameter design. An ARSEP inverter prototype was designed, simulated, and constructed to verify its performance and benefits. Compared to a conventional hard-switched inverter with a ${dv/dt} $ filter, the ARSEP inverter prototype results in a significant reduction in overall power loss, inductor volume, and weight.

Application of Power Electronic Circuitry for Elimination of Flywheel in Process Machines

It is felt highly probable to eliminate flywheel from the design of any process machine in general and for process machines with a certain demand torque characteristics in particular. It is felt that by proper interfacing of power electronic devices this may be possible. Elimination of flywheel from process machines helps reducing torsional vibrations in the power transmission system of any process machine. This should reduce fatigue in the components of power transmission system thereby prolonging equipment functional failure. Down time will be much less and profit earnings through uninterrupted production would be high. This paper proposes a convenient power electronic circuitry with reasonable control approach for the flywheel replacement of an induction motor for which it is necessary to generate supply torque at motor shaft exactly equal to demand torque. To meet this requirement, demand torque characteristic is sampled at 25 msec. In proposed solution to this problem, the torque requirement at every sample is met by adjusting the firing angle of thyristors which in turn adjusts the supply voltage at motor terminals. Depending on supply frequency the sampling period for demand torque characteristic may be varied. The present paper has a focus of evolving the details of functional feasibility of this concept only.

Overvoltage at motor terminals in SiC-based PWM drives

Key points in the development of More Electrical Aircraft (MEA) are currently DC power distribution in higher voltage levels (540 V) and the use of disruptive technology such as Wide BandGap (WBG) semiconductors in power inverters. Using WBG components (SiC and GaN) increases the power converter mass density. However, fast switching of WBG components (tens of kV/μs) induces voltage transient overshoots due to parasitic elements within the inverter. In addition, propagation and reflection phenomena along the harness connected to this inverter, even for small lengths, cause a significant voltage overshoot across the loads. Such overvoltage in Adjustable Speed Drives (ASD: association of inverter, harness and motor) supplied by the new HVDC 540 V aeronautical network could be fatal for the Electrical Insulation System (EIS). This paper proposes a fast and accurate modeling methodology to predict transient overvoltage; it allows us to analyze the impact of SiC inverter technology on overvoltage at motor terminals.

Multiphysics Design of a V-Shape IPM Motor

In this paper, a multiphysics model is proposed for a multi-V-shape interior permanent magnet motor with concentrated winding. This paper develops a nonlinear magnetic model that computes the flux density in the motor. The analytical model includes several novel aspects: it takes into account the local saturation near the iron bridges, it proposes a method for modeling the concentrated tooth winding, and it calculates the slot tangential leakage flux and includes it in the flux linkage calculation. The magnetic model is coupled with an electrical model that computes the power factor and the voltage at the motor terminals. A loss model is developed in order to calculate the copper and the iron losses. They are used as inputs to a nodal thermal model that introduces a thermal circuit for concentrated end-winding and computes the temperature of the motor. A mechanical model is developed. It evaluates the mechanical constraints encountered by the structure. The models are verified using finite element computations and numerical calculations performed with dedicated software. Besides, the coupled analytical model is experimentally validated using a prototype motor. Finally, two multiphysics bi-objective optimizations are carried out in order to design the motor for high-torque and low-speed application.

Algorithms for building distribution networks of electricity supply, reducing losses of electricity

The basis for achieving high quality of electricity are three components: high-quality power generation, uninterrupted transmission and distribution over reliable networks. In conditions of commensurability of the power of electric motors with the power supply and with a considerable extension of the cable network, algorithms for automated design of the power supply system are needed. This article describes an approach based on the application of the Dijkstra algorithm, which allows to reduce costs in the construction of the distribution network and provide the necessary voltage level at the motor terminals or minimum energy losses in the cable network. The main and arbitrary structure of a power supply network with an electric load in terms of the theory of the genetic algorithm is described, on the basis of which it is possible to create an effective means of determining rational configurations of a power supply network with an electric load.

Parvalbumin expression affects synaptic development and physiology at the Drosophila larval NMJ

Presynaptic Ca2+ appears to play multiple roles in synaptic development and physiology. We examined the effect of buffering presynaptic Ca2+ by expressing parvalbumin (PV) in Drosophila neurons, which do not normally express PV. The studies were performed on the identified Ib terminal that innervates muscle fiber 5. The volume-averaged, residual Ca2+ resulting from single action potentials (APs) and AP trains was measured using the fluorescent Ca2+ indicator, OGB-1. PV reduced the amplitude and decay time constant (τ) for single-AP Ca2+ transients. For AP trains, there was a reduction in the rate of rise and decay of [Ca2+]i but the plateau [Ca2+]i was not affected. Electrophysiological recordings from muscle fiber 5 showed a reduction in paired-pulse facilitation, particularly the F1 component; this was likely due to the reduction in residual Ca2+. These synapses also showed reduced synaptic enhancement during AP trains, presumably due to less buildup of synaptic facilitation. The transmitter release for single APs was increased for the PV-expressing terminals and this may have been a homeostatic response to the decrease in facilitation. Confocal microscopy was used to examine the structure of the motor terminals and PV expression resulted in smaller motor terminals with fewer synaptic boutons and active zones. This result supports earlier proposals that increased AP activity promotes motor terminal growth through increases in presynaptic [Ca2+]i.

Inter-relationships among physical dimensions, distal–proximal rank orders, and basal GCaMP fluorescence levels in Ca2+ imaging of functionally distinct synaptic boutons at Drosophila neuromuscular junctions

GCaMP imaging is widely employed for investigating neuronal Ca2+ dynamics. The Drosophila larval neuromuscular junction (NMJ) consists of three distinct types of motor terminals (type Ib, Is and II). We investigated whether variability in synaptic bouton sizes and GCaMP expression levels confound interpretations of GCaMP readouts, in inferring the intrinsic Ca2+ handling properties among these functionally distinct synapses. Analysis of large data sets accumulated over years established the wide ranges of bouton sizes and GCaMP baseline fluorescence, with large overlaps among synaptic categories. We showed that bouton size and GCaMP baseline fluorescence were not confounding factors in determining the characteristic frequency responses among type Ib, Is and II synapses. More importantly, the drastic phenotypes that hyperexcitability mutations manifest preferentially in particular synaptic categories, were not obscured by bouton heterogeneity in physical size and GCaMP expression level. Our data enabled an extensive analysis of the distal–proximal gradient of GCaMP responses upon genetic and pharmacological manipulations. The results illustrate the conditions that disrupt or enhance the distal–proximal gradients. For example, stimulus frequencies just above the threshold level produced the steepest gradient in low Ca2+ (0.1 mM) saline, while supra-threshold stimulation flattened the gradient. Moreover, membrane hyperexcitability mutations (eag1 Sh120 and parabss1) and mitochondrial inhibition by dinitrophenol (DNP) disrupted the gradient. However, a novel distal–proximal gradient of decay kinetics appeared after long-term DNP incubation. We performed focal recording to assess the failure rates in transmission at low Ca2+ levels, which yielded indications of a mild distal–proximal gradient in release probability.

Importance of Full-Collapse Vesicle Exocytosis for Synaptic Fatigue-Resistance at Rat Fast and Slow Muscle Neuromuscular Junctions.

Neurotransmitter release during trains of activity usually involves two vesicle pools (readily releasable pool, or RRP, and reserve pool, or RP) and two exocytosis mechanisms (“full-collapse” and “kiss-and-run”). However, synaptic terminals are adapted to differing patterns of use and the relationship of these factors to enabling terminals to adapt to differing transmitter release demands is not clear. We have therefore tested their contribution to a terminal’s ability to maintain release, or synaptic fatiguability in motor terminals innervating fast-twitch (fatiguable), and postural slow-twitch (fatigue-resistant) muscles. We used electrophysiological recording of neurotransmission and fluorescent dye markers of vesicle recycling to compare the effects of kinase inhibitors of varying myosin light chain kinase (MLCK) selectivity (staurosporine, wortmannin, LY294002 & ML-9) on vesicle pools, exocytosis mechanisms, and sustained neurotransmitter release, using postural-type activity train (20 Hz for 10 min) in these muscles. In both muscles, a small, rapidly depleted vesicle pool (the RRP) was inhibitor insensitive, continuing to release FM1-43, which is a marker of full-collapse exocytosis. MLCK-inhibiting kinases blocked all remaining FM1-43 loss from labelled vesicles. However, FM2-10 release only slowed, indicating continuing kiss-and-run exocytosis. Despite this, kinase inhibitors did not affect transmitter release fatiguability under normal conditions. However, augmenting release in high Ca2+ entirely blocked the synaptic fatigue-resistance of terminals in slow-twitch muscles. Thus, full-collapse exocytosis from most vesicles (the RP) is not essential for maintaining release during a single prolonged train. However, it becomes critical in fatigue-resistant terminals during high vesicle demand.