Motor Start-up Research Articles

A soft-startup device for an induction motor with supply-network voltage control

The use of a thyristor voltage converter to limit voltage dips during the induction motor startup is considered. It is shown that the traditional solution—the current-cutoff startup mode—does not solve the problem of maintaining the residual voltage at supply-network bars during the motor startup at a level, at which the uninterrupted operation of other equipment connected to this supply network is provided. To limit the voltage dips during the startup, it is necessary to control the supply voltage during the startup. A control-system structure of the thyristor soft starter, which implements a closed loop of supporting the supply-network voltage during the startup, and the synthesis procedure of a controller in this structure are proposed. It is shown that the controller, which is created based on a simplified object model, gives acceptable results in practical use. Results of modeling and experimental data that show the operability of the proposed approach are presented. The desired supply-network voltage is directly set to the input in the system with the voltage control, and the possibility of maintaining this voltage during the induction-motor startup with the structural and parametric variations in the supply network and load is provided with high accuracy and adequate quality of transient processes.

Mathematical rotordynamic model for lateral vibration analysis of induction motors with dynamic eccentricities regarding start-up

The paper shows a mathematical rotordynamic model for lateral vibration analysis of induction motors with dynamic eccentricities regarding start-up. With this mathematical model, different kinds of dynamic eccentricities—mass eccentricity, magnetic eccentricity and bent rotor deflection—can be analyzed. Beside the mechanical influences—e.g. the rotor mass, rotor shaft stiffness, oil film coefficients of the sleeve bearings, structural stiffness of the sleeve bearing housings and end shields—also electromagnetic influence—e.g. the electromagnetic field and magnetic eccentricity—can be analyzed for the start-up. The paper is based on the well-known theory of accelerated resonance passing and is an enhancement of the theory for induction motors, considering also electromagnetism during start-up. Based on this rotordynamic model, the absolute displacements of the shaft centre, the shaft journals and the sleeve bearing housings can be analyzed as well as the relative displacements between the shaft journals and the sleeve bearing housings. Additionally, also the vibration velocities at the sleeve bearing housings can be derived. The aim of the paper is not to replace a detailed finite-element-model by a simplified analytical model, but to show the mathematical coherences between rotordyamics and electromagnetics for a start-up of an induction motor, considering different dynamic eccentricities.

The Energy Saving Pumping Unit System Design and Analysis

With the development of oil field production demand today, pumping unit is developing towards the direction of energy saving, intelligent. According to the present status of the oilfield, this paper designed a kind of intelligent energy saving pumping unit system, the system acceleration and deceleration process is very short, most of their working time in uniform motion in a stroke, and the beam pumping unit has been alternating deceleration process all the time compared with good energy saving effect. Energy store system is designed, the system not only reduces energy consumption, and make the motors can be started with initial velocity, shorten the motor start-up time, the motor starting current is stable running current of 4 to 7 times, so that reduces the starting current impact. To test this idea, modeling of motor, and the simulation analysis, the results confirmed the idea very well. Finally, in the principle of the pumping unit system prototype experiments, the experimental results show that the pumping unit system has significant energy-saving effect and the intelligent characteristics.

Reactive Power Coordination of Shipboard Power Systems in Presence of Pulsed Loads

Voltage and reactive power control is a fundamental issue in all-electric shipboard power systems (SPS). However, coordination between generation and propulsion management to match reactive power is poor in current SPS designs. This paper presents a new model predictive control based dynamic Volt/Var control scheme to control the voltage in the system. This method uses a dynamic model of the sources and loads and finds the optimal reactive control inputs to the system to minimize the voltage deviations in the future. Since this method uses prediction of the reactive demand of pulsed loads, it is able to achieve a smooth voltage profile in the SPS in presence of pulsed power loads. This method is also able to control voltage of the system during propulsion motor startup. The controller is tested in presence of high power pulsed loads in the system. The results demonstrate that the dynamic reactive controller is able to keep the voltage profile of the system smooth and within system limits.

A Control System to Reduce Torque Pulsation During Start-Up of AC Electrical Machines

This paper presents a control system for reducing electromagnetic torque amplitude and pulsation during start-up of a three-phase induction motor. The control system is based on a new method of non-simultaneous connection of voltage phases. The effectiveness of the proposed system is shown through a simulation and an experimental verification of start-up of an squirrelcage induction motor.

Potential Power Quality Benefits of Electric Vehicles

Electric vehicles (EVs) are likely to have a continued presence in the light-vehicle market in the next few decades. As a result, EV charging will put an extra burden on the distribution grid and adjustments need to be made in some cases. On the other hand, EVs have the potential to support the grid as well. This paper presents a single-phase bidirectional charger topology which pairs up a photovoltaic (PV) source with an EV charger resulting in production cost reduction. The presented topology is then used for vehicle-to-grid (V2G) services. The main focus of this paper is on power quality services which only slightly discharge the battery. Among these services, it studies the possibility of local reactive injection of EVs connected to the grid through a single-phase charger to compensate for voltage drops caused by motor startup or inductive loads. It also studies the possibility of active power injection of EVs for short time periods during PV transients in cloudy weather to keep the system stable. It also studies the potential of EVs to help during low voltage ride-through of the PV sources. The studies are performed using Simulink simulations and a real-time implementation in Real Time Digital Simulator (RTDS). The results demonstrate the effectiveness of power quality V2G services with small wear on the EV battery.

Energy saving in case of intermittent production by retrofitting service plant systems through inverter technology: a feasibility study

Many production machines have high energy consumption due to the large number of electrical motors used to rotate equipment, such as tools, fans and pumps. Moreover, in different industrial sectors production is not continuous but intermittent, where working times alternate with idle times. During idle times continuous switch off is not always possible due to technical limitations, and if it is possible, it can cause higher energy consumption due to peak current at the start-up of the electrical motors. The purpose of this paper is to introduce the possibility of managing intermittent production using inverter technology. The inverter provides power control by managing the frequency and voltage of the power supplied to the alternating current motors. The study analyses the potential energy consumption reduction as a function of the production parameters (number of daily stops, average working time, etc.) and develops a feasibility analysis, its related investment cost and its potential energy consumption reduction. As a result, the proposed feasibility study defines the set of production parameters and the types of equipment for which this technology is suitable, bringing rapid investment payback. The proposed feasibility analysis is validated by an industrial case study related to a tannery spray plant.

The Boot Method Analysis of Three-Phase Asynchronous Motor

The boot method of three wound-rotor asynchronous motors and three-phase squirrel-cage asynchronous motor are described; As to reduce the start current and to increase the starting torque, the principle of all kinds of startup methods are analyzed; the advantages and disadvantages of various starting methods are evaluated; Development directions of modern motor startup are pointed out.

Induction Motor Starting in Islanded Microgrids

Motor loads require high amount of reactive power for a short period during their startup. The high reactive power drawn from the system causes voltage dips at startup time and potentially overvoltage after motor startup is over. The voltage dip and overvoltage may cause the relays to trip and the system to go unstable. This phenomenon is more challenging in weak distribution systems and isolated systems such as microgrids due to the limited inertia of the master generator. This paper presents a dynamic voltage controller that coordinates all the reactive power sources in the system to provide the necessary reactive power during motor startup. The presented Model Predictive Control (MPC) based dynamic Volt/Var Control (VVC) scheme considers the dynamics of the microgrid in the VVC formulation to overcome the voltage dip caused by motor startup. This method uses predictions of voltage behavior of the system based on a simplified system model and tries to eliminate the effect of motor startup by coordinating the reactive power sources in the system.

Modeling and Analysis of Voltage Sag Sources in Distribution Network

The mechanism of voltage sags due to three main voltage sag sources, such as line faults, startup of large induction motor and transformer energization, was analyzed theoretically. Based on the typical structure of the distribution network of a large industrial enterprise, the paper presented a simplified analytical model for voltage sag sources and conducts a test with the above three kinds of voltage sag sources in Matlab/Simulink. The results show the proposed model is correct and suitable for the analysis of distribution network.

Analysis of Maximum Angle of Mismatch between Half Couplings of a Magnetic Clutch and Highly Coersive Permanent Magnets

A procedure is proposed for analysis of maximum mismatch angle between the half couplings of a magnetic clutch and highly coersive permanent magnets (formed from alloys of rare-earth elements ‐ samariumcobalt and neodium-iron-boron) during the start-up of an asynchronous motor is proposed for the design of hermetically sealed machines (pumps, compressors, mixers, etc.). In hermetically sealed machines with a magnetic clutch (pumps, vacuum cleaners, compressors, mixers), the driving and driven parts are coupled elastically one with the other, and are displaced relative to one another by an angle that varies during movement (the mismatch angle of the poles of the magnetic clutch). Prior to start-up of the driving asynchronous electric motor, the magnets of a cylindrical magnetic clutch are situated coaxially, and the half couplings opposite one another. The forces of interaction between the magnets are directed toward the center of the axis of rotation of the clutch along lines connecting the centers of the poles of the magnets. The torque of the clutch is equal to zero in this position. During start-up, the driving half couple, which is mounted on the shaft of a driving electric motor, is turned through a certain angle, while the driven half clutch, which is mounted on the shaft of the effective member of the machine, remains in place, since the connection between the half couplings is not rigid. Moreover, the centers of the poles of the magnets are also displaced relative to one another by this same angle, and the directions of the interaction forces of the magnets are changed ‐ tangential components of the interaction forces are manifested. A torque develops in the clutch under the action of all tangential magnetic forces. When the torque of the clutch is greater than the torques created by the resistance forces (friction, load, and inertia), the driven half coupling is withdrawn beyond the driving half coupling, and an additional load develops on the driving electric motor, which lowers its dynamic torque. The acceleration of the driving half coupling is reduced, and the driven half coupling approaches the driving half coupling. As a result, the load, mismatch angle, and torque of the clutch (acting on the driving half clutch) are reduced, and the driving motor is again accelerated, leading to an oscillatory process. The maximum torque transferred by the clutch should exceed the in-service torsional moments due to the resistance forces in order to avoid breaking of the magnetic bond between the half couplings (rotations of the half couplings with different frequencies, resulting in a marked reduction in the torque being transferred). It should be pointed out that after the pause associated with restoration of the broken magnetic bond, the torque of the clutch is fully restored ‐ i.e., the clutch can be used as a protective link. After acceleration from rest, the torque transferred by the clutch is reduced (consequently, the mismatch angle is also reduced) due to disappearance of acceleration of the rotating masses, and the effective operating regime of the clutch and machine is established.

Start-Up and Low-Speed Operation of an Electric Motor Driven by a Modular Multilevel Cascade Inverter

This paper describes start-up and low-speed operation of an electric motor driven by a modular multilevel cascade inverter based on double-star chopper cells. This paper proposes a square-wave method to suppress the peak circulating current. The theoretical analysis developed in this paper reveals that the peak circulating current when using the square-wave method gets smaller by 50% than that when using the sinusoidal-wave method proposed in the previous work. The experimental results obtained from a 400-V 15-kW downscaled system verify that stable operation is achieved at an ultralow speed of 17 min <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with a load torque of τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> = 40%, as well as “three-phase” dc-current feeding operation. Moreover, the motor can start up from a standstill without producing any overvoltage or overcurrent.

Monolithic H‐bridge brushless DC vibration motor driver with a highly sensitive Hall sensor in 0.18 μm complementary metal‐oxide semiconductor technology

A monolithic low-voltage H-bridge brushless DC (BLDC) vibration motor driver with an integrated high sensitivity Hall sensor has been presented in 0.18 μm high-voltage complementary metal-oxide semiconductor technology. To improve the motor start-up reliability, a full-on start mode is applied to realise a high-speed start sequence by shortening the start-up time. Meanwhile, an active start function is activated to prevent dead point phenomenon if the motor magnet pole sensed by the built-in Hall sensor does not change during the motor starting. This complete one-chip solution for driving the BLDC vibration motors provides significantly enhanced reliabilities, including thermal shutdown and under voltage lockout protection functions, and fully eliminates the need for any external components. The measured results show that the motor driver chip has a typical operating point of 2 mT and a typical releasing point of − 2 mT, showing a hysteresis magnetic property of 4 mT. The chip is very robust. It can operate well within a low supply voltage range of 2–4 V and can output a maximum of 300 mA peak current while the ambient temperature ranges from − 40 to 85°C.

Investigation on the Ignition Over Pressure Related to Launch Vehicle Lift-of.

Several transient events occur during the startup of the Solid Rocket Motor (SRM) during the launch vehicle lift-off. Each event produces a complex transient signal and requires systematic assessment. The event discussed in this paper is Ignition Over Pressure (IOP). This Ignition Over Pressure is resulting from fluid dynamic compression of the accelerating plume gas, subsequent rarefaction and propagation during the pressure rise rate period in the rocket combustion chamber. These high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and its surrounding structure. This wave behaves as a blast or shock wave characterized by a positive triangular shaped first pulse and negative half sine wave second pulse. The pulse travels upwards towards the propulsion system and has the potential to overload the individual elements or exciting overall vehicle dynamics. The later effect results from the phase difference of the wave from one side of the vehicle to the other due to the skew in the ignition of the strap-on boosters. In the case of the launchers, the mechanical stress due to the ignition over pressure wave comes, in addition to the acoustic constraint due to the jet noise. The over pressure phasing or ΔP environment, because of its spectral content as well as amplitudes becomes a crucial input for the design of sub-assemblies viz., thermal shields, and pay loads etc. In this paper, an attempt is made to numerically visualize the propagation of the blast wave causing the unsteady pressure oscillations during the transient pressure rise in the combustion chamber. To understand further, pressure measurements have been made at different heights along the umbilical tower during the solid rocket motor lift-off with the presence of jet deflectors, in order to capture the shock propagation phenomena. From the results, it appears that a sudden shock front that is generated during flow development within the rocket nozzle leaves a clear signature in the form of a well defined peak at typical time intervals. This overpressure amplitude seems to be related to the slope of the combustion chamber pressure rise rate during the transient period. It is also observed that the shock front initially propagates at supersonic speed but decays with time later. Similarly, the magnitude of the IOP peaks are also seen to decay with distance.

Model Reference Adaptive System Based Adaptive Speed Estimation for Sensorless Vector Control with Initial Rotor Position Estimation for Interior Permanent Magnet Synchronous Motor Drive

The rotor position/speed sensor used to control the permanent magnet synchronous motor drive has increased size and cost, decreased reliability, and a need for shaft extension and mounting arrangements. Sensorless control is currently adopted in many industrial applications for reasons of robustness, cost, cabling, and reliability. In order to achieve correct operation from zero speed startup of a sensorless salient-pole permanent-magnet synchronous motor (the interior permanent magnet synchronous motor), the initial rotor position of the motor is required. A model reference adaptive system technique has been used for speed estimation in sensorless speed control of the interior permanent magnet synchronous motor with space vector pulse width modulation. This article presents a new approach to improved initial rotor position detection of an interior permanent magnet synchronous motor. The method uses a suitable sequence of short and long time voltage pulses applied to the stator coil at standstill. Short time voltage pulses are applied to the motor terminals to detect the initial rotor position. Long time voltage pulses are used for detection of the magnet polarity based on the effect of saturation. The measurement of the current peaks values gives information about the initial rotor position. Simulation and experimental results are presented and show the validity of the proposed method, which is capable of reliable initial rotor position detection, including the polarity of the magnet at standstill. The error initial rotor position detection is less than 5 mechanical degrees. Experimental results are presented for an interior permanent magnet synchronous motor obtained on a fixed-point digital signal processor based control system. Experimental results show that the modeled reference adaptive system technique speed estimation provides high-performance sensorless control and initial rotor position estimation algorithms of the interior permanent magnet synchronous motor drive.

Fast Evaluation Methods for Voltage Sags in Ship Electrical Power Systems

Induction motors are widely used in ship electrical power applications as they are frequently switched on into the supply system, consuming about 70% of the electrical energy generated. Voltage sag, which is produced by the starting current of induction motors, is one of the main causes of sensitive equipment dropout and, as such, must be considered in ship electrical system designs to comply with classification societies' rules. A simple and fast method that is able to estimate the expected magnitude of voltage sag disturbances and provide information about the effectiveness of the various mitigation methods is essential. This paper aims at presenting a faster evaluation method for voltage sags due to motor start-ups in ship electrical power systems. The performance of the proposed method is validated by measurements gathered from several motor starter designs in practical ship power applications using the Riemann-summation-principle-based evaluation method. The proposed method can provide engineers with useful information about the actual magnitude of sag disturbances as well as on the effectiveness of motor starters for ship electrical power applications, which will assist them in determining proper motor starter designs.

Design and implementation of sensorless DC inverter-fed compressor drive system

A novel proportional–integral–derivative neural network (PIDNN) controller is proposed to replace the PI controller, which is adopted in conventional high-frequency signal injection to improve the speed estimating performance for start-up and low speeds of the interior permanent magnet synchronous motor (IPMSM) used in DC inverter-fed compressor drive systems. Moreover, two sensorless control schemes are also proposed for the IPMSM drive system. One is the high-frequency signal injection method combined with the commutation-signal-based (CSB) speed estimation method, and the other is the high-frequency signal injection method combined with the model reference adaptive system (MRAS) speed estimation method. Both sensorless control schemes use high-frequency signal injection as the start-up strategy to achieve sinusoidal starting. When the motor speed gradually increases to a preset speed, the sensorless drive will switch to the CSB speed estimation method or the MRAS speed estimation method for high-speed control. The theories of the high-frequency signal injection method, the CSB and MRAS speed estimation methods and the PIDNN controller are introduced in detail. Furthermore, a DSP-based computer control system is developed to implement the sensorless DC inverter-fed compressor drive system and some experimental results are given to verify the feasibility of the proposed control schemes.

Control system of start-up of the asynchronous motor

In article the creation of a control system considered a question by the frequency and regulated asynchronous electric drive at the feed of a stator of the motor by the stabilized current which provides startup with a constant of the electromagnetic moment without use of special sensors

A Performance Investigation and Comparison of Line Start-up Permanent Magnet Synchronous Motor with Super Premium Efficiency

This paper presents the performance investigation and design technology of a Line Start-up Permanent Magnet Synchronous Motor (LSPMSM) with super premium efficiency, including a design consideration and evaluation for motor start-up, key performance, and advanced finite element analysis FEA) for the design, improvement and verification, prototype build and test, design and test data comparison with a <TEX>$Premium^{(R)}$</TEX> Efficient Induction Motor (PEIM). To assess the design technology, the LSPMSM prototype was built amended from a PEIM with the same frame, stator punching and rated output. Based on the prototype test, two novel design improvements and analyses have been done to eliminate noise and vibration. Additionally, the comparisons with the PEIM on the power factor, efficiency, frame size and active material consumption indicated that a significant performance improvement and active material cost reduction can be achieved by the LSPMSM.

Novel indices for broken rotor bars fault diagnosis in induction motors using wavelet transform

This paper introduces novel indices for broken rotor bars diagnosis in three-phase induction motors based on wavelet coefficients of stator current in a specific frequency band. These indices enable to diagnose occurrence and determine number of broken bars in different loads precisely. Besides thanks to the suitability of wavelet transform in transient conditions, it is possible to detect the fault during the start-up of the motor. This is important in the case of start-up of large induction motors with long starting time and also motors with frequent start-up. Furthermore, broken rotor bars in induction motor are detected using spectra analysis of the stator current. It is also shown that rise of number of broken bars and load levels increases amplitude of the particular side-band components of the stator currents in the faulty case. An induction motor with 1, 2, 3 and 4 broken bars at the rated load and the motor with 4 broken bars at no-load, 33%, 66%, 100% and 133% rated load are investigated. Time stepping finite element method is used for modeling broken rotor bars faults in induction motors. In this modeling, effects of the stator winding distribution, stator and rotor slots, geometrical and physical characteristics of different parts of the motor and non-linearity of the core materials are taken into account. The simulation results are are verified by the experimental results.