Line-start Motor Research Articles

Parametric Analysis for Performance Optimization of Line-Start Synchronous Motor with Interior Asymmetric Permanent Magnet Array Rotor Topology

Line-start synchronous motors have attracted researchers’ interest as suitable replacements of asynchronous motors due to their high efficiency, which has been provoked by strict regulations regarding applicable efficiency classes of motors in the EU market. The research becomes even more challenging as it takes into consideration the diverse rotor topologies with different magnet locations for this type of motor. The rotor configuration with an interior asymmetric permanent magnet (PM) array rotor was chosen for analysis and optimization in this paper as this specific configuration is particularly challenging in terms of placing the magnets with adequate dimensions into the existing rotor of the asynchronous motor with a squirrel cage winding, in order simultaneously to obtain good operational characteristics such as high efficiency and power factor, good overloading capability and low material consumption. Therefore, an optometric analysis is performed in order to find the best configuration of the air gap length, magnet thickness, magnet width and number of conductors per slot, along with modifications of the rotor slot. The motor outer dimensions remained unchanged compared with the starting model of the line-start motor derived from the asynchronous motor, which is a product of the company Končar. The optimized model obtained higher efficiency, power factor and overloading capability than the starting model, along with good starting and synchronization capabilities.

Comparative Analysis of Line-start Synchronous Motor and Asynchronous Motor

Energy efficient motors are the key components of each industrial process. In the energy demanding society, requiring the energy efficient consumers, the line-start synchronous motor has gained more and more popularity due to the high efficiency and power factor combined with good operational characteristics. The disadvantages of the synchronous motors such as inability of starting without the inverter has been largely overcame with this type of the motor. However, the proper design of line-start motor regarding permanent magnets and the squirrel cage winding is crucial for motor starting and synchronization capability. In this paper, the line-start synchronous motor is derived from the asynchronous motor by redesigning the rotor. The obtained performance characteristics of the synchronous motor is compared with the data of the asynchronous motor (the analytical, measurements and from the motor producer) and they show reasonable agreement. The derived model of the synchronous motor is numerically modelled for obtaining the magnetic flux density distribution in the motor cross-section. The analysis and comparison is completed by obtaining the transient characteristics of both types of the motors. The designed synchronous motor has proven to have good starting and synchronization capabilities combined with the high efficiency. The dynamic response at sudden load changes is within expected limits.

Life Cycle Energy Cost Assessment for Pump Units with Various Types of Line-Start Operating Motors Including Cable Losses

The paper presents a comparative analysis of life-cycle energy consumption for three different types of 4 kW line-start motors used in a pump unit with throttling: the most widely used induction motor with IE3 efficiency class, line start permanent magnet synchronous motor with IE4 efficiency class and line start synchronous reluctance motor with IE4 efficiency class. The operating cycle for pump units with constant flow is considered for the above-mentioned types of motors taking into account not only the losses in the pump and motor, but also in the power supply cable. It is shown that the line start synchronous reluctance motor without magnets has the highest efficiency over the entire considered loading range. However, its power factor is lower than that of the synchronous motor with magnets and therefore it has more significant losses in power supply cable. Despite this disadvantage, the line-start reluctance motor is a good alternative to widespread induction motor since it allows saving of approximately 4000 euro more than the latter during the 20 years life cycle. It also provides similar savings in comparison to the permanent magnet synchronous motor, but unlike it, it does not have costly rare-earth materials in the rotor.

Optimal Design of 1 Phase Linear Oscillatory PM Motor Series for Small Compressor Like Drives: With FEM and Self-Starting Transients Validation

Refrigerator compressors are currently driven mostly by rotary line start or variable-speed (inverter-fed) motors with mechanical transmission. Direct driving of pistons by linear oscillatory resonant PM 1 phase motors has just been introduced to low power (less than 100 W) such applications. The present paper introduces a 3 pole PM mover 1 phase PM linear oscillatory motors, in terms of optimal nonlinear analytical design methodology, with FEM and dynamics validation. Both 50 and 250 Hz (inverter fed) operation for 2000 and 100 W is exemplified for minimum active materials costs and, respectively, minimum global costs (losses capitalized cost is added). For the line start case study (at 2000 W, 50 Hz) a circuit model for transients is introduced and the motor self-starting transients with full power delivery at above 91% efficiency is available. The 50 Hz motors are heavier around (5.7 kg/kW at 2000 W and 7.5 kg/kW at 100 W, respectively) than the 250 Hz motors around (1.2 kg/kW, 3 kg/kW) but the latter require inverter control.

Dynamics of the line-start reluctance motor with rotor made of SMC material

Abstract Design and control of electric motors in such a way as to ensure the expected motor dynamics, are the problems studied for many years. Many researchers tried to solve this problem, for example by the design optimization or by the use of special control algorithms in electronic systems. In the case of low-power and fractional power motors, the manufacture cost of the final product is many times less than cost of electronic system powering them. The authors of this paper attempt to improve the dynamic of 120 W line-start synchronous reluctance motor, energized by 50 Hz mains (without any electronic systems). The authors seek a road enabling improvement of dynamics of the analyzed motor, by changing the shape and material of the rotor, in such a way to minimize the modification cost of the tools necessary for the motor production. After the initial selection, the analysis of four rotors having different tooth shapes, was conducted.

A Review of the Methods for Improving the Efficiency of Drive Motors to Meet IE4 Efficiency Standards

High efficiency standards are slowly being introduced with IE3 efficiency levels shortly becoming compulsory in many countries; IE4 efficiency levels being developed for future implementation. In this paper a review is carried out of the IE 60034-30 standard which covers standard line-start induction motors. Some design techniques that can be used to increase efficiency in order to meet the IE4 standards are discussed. This standard is now being replaced by the IE60034-30-1 standard which extends to other line start motors and also IE 60034-30-2 is being introduced to cover variable speed drives in order to address developing technology. The conclusion is that IE4 standards are obtainable but careful design is needed to reach this. Examples from the literature are given.

Running up and pulling into step of PM line-start motors with surface-mounted magnets

Permanent magnet (PM) synchronous motors with starting cage, already developed in the 1960s for variable-speed textile drives, become increasingly important as energy-efficient PM line-start motors. Differing from the standard design with integrated magnets, a rotor design with surface-mounted magnets is presented. In the planning and design phase of drives with PM line-start motors, the simulation of switching on, running up, and pulling into step is essential. An analytical model is presented leading to voltage and mechanical differential equations that have to be solved simultaneously. Based on a prototype, the suitability of the presented model is demonstrated by direct comparison of simulated to measured data. Besides, the mean influence factors of the pulling-into-step behavior are identified and discussed.

Line‐start permanent magnet motors: proper design for pole‐changing starting method

Pole-changing of line-start permanent magnet (LSPM) motors at start-up eliminates all their drawbacks such as poor starting torque, vibration at start-up and synchronisation problems. In addition, by using this method almost all the inherent limitations in the design parameters of line-start motors such as rotor resistance, permanent magnet strength and mechanical stress influenced by pulsating torques are alleviated. Therefore there is no need to compromise between the motor parameters. In this study, the design procedure of these motors is investigated and a high-performance motor based on the pole-changing starting-method is designed and fabricated. Next, the possibility and advantages of replacing laminated cage-bar rotors with solid rotors are investigated for pole-changing LSPM motors. Then, simulations are done by the two-dimensional finite element method and finally, the experimental results are presented. The good agreement between simulation and experimental results validates the theoretical method and also the new design.

A study on oscillatory and effective torques of an line-start PM motor in start-up operation

In this paper, various effective and oscillatory torque components in a line-start permanent magnet (LSPM) motor are analyzed using the principle of superposition through the analytic approach with an equivalent circuit. According to the independent sources, in the asynchronous speed the induced rotor current and braking stator current are derived by using the DQ equivalent circuit and Laplace transformation. Then, two effective components and three oscillatory components of torque are calculated quantitatively by using the analytic torque equations. Finally, to check usefulness of the proposed method, the current and torque characteristics are compared with finite element analysis and measurement results for various speeds.

SLOT-LESS TORUS SOLID-ROTOR-RINGED LINE-START AXIAL-FLUX PERMANENT-MAGNET MOTOR

This paper presents the design, analysis, and prototyping of a novel axial-∞ux permanent-magnet (AFPM) motor capable of auto-starting. The preliminary design is a slot-less double-sided solid-rotor line-start AFPM motor with 4 poles for high torque density and stable rotation. One spaced raised ring was added to the inner radii of the rotor disc for smooth line-start motor. The design allows the motor to operate at both starting and synchronous speeds. The basic equations for the solid ring of the rotor of the proposed axial-∞ux permanent-magnet motor are presented. Non- symmetry of the designed motor led to its 3D time-stepping flnite element analysis (FEA) via ANSYS 13.0, which evaluated the design parameters and predicted the transient performance. The designed motor was fabricated and tested, the experimental results showing good agreement with FEA simulation results. The prototype motor showed high starting torque and good synchronization.

Effects of Magnetizing Inductance on Start-Up and Synchronization of Line-Start Permanent-Magnet Synchronous Motors

The capabilities of proper start-up and synchronization are important issues in the design of line-start permanent magnet synchronous motors. Failing in early start-up or in synchronization under certain conditions prevents the widespread use of these motors. In order to draw useful guidelines for the design of line-start permanent magnet synchronous motors, the contradictory effects of a large value of magnetizing inductance in improving early start-up and deteriorating synchronization of line-start permanent magnet synchronous motors are analyzed in this paper. The analysis is done through three different methods. First, the effect of magnetizing inductance on average and pulsating torques of the motors during asynchronous operation is investigated and the role of these torques in start-up and synchronization performances of the motors is discussed. A critical load is then determined in terms of motors parameters as a torque limit above which the motors cannot start. The effect of magnetizing inductance, magnet flux, and saliency on the critical load is also investigated. A dynamic d-q model of the motors is then implemented to support the discussions by analyzing two line start motors with different magnetizing inductances. Finite-element-based analyses are then carried out for both motors to consider motors parameters variation, skin effect, saturation, rotor asymmetry, and cross magnetization. A good agreement between the finite-element method and dynamic simulation results is evident. Finally, some design guidelines are proposed for the proper selection of the magnetizing inductance in motor designs for different applications.

Comparative Study of Starting Methods for a Single-Phase Permanent Magnet Synchronous Motor

This paper compares three starting methods for a single-phase interior permanent magnet synchronous motor. One is a line-start capacitor motor with a starting cage. The second is the same cage motor with an open-loop variable-voltage fixed-frequency inverter. The third uses the same motor without its starting cage, fed from a closed-loop current-regulated inverter with shaft position feedback. The computed starting performance is compared with test data for all three cases.

Analysis of irreversible magnet demagnetization in line-start motors based on the finite-element method

This paper deals with the analysis for the irreversible demagnetization characteristics of a ferrite-type permanent magnet in the line-start motor using the two-dimensional finite-element method (2-D FEM). The demagnetizing currents are calculated from the transient analysis in the combination voltage equation with mechanical dynamic equation, and peak currents are applied to the irreversible demagnetization analysis computed by 2-D FEM. The nonlinear characteristic of the magnetic core is considered as well as that of a permanent magnet on the B-H curve in the analysis of irreversible demagnetization.

The design of high-efficiency line-start motors

The design of high-efficiency line-start motors

Single-Phase Permanent-Magnet Motor Analysis

A unified theoretical approach is presented for the calculation of the performance of the single-phase capacitor-start permanent-magnet (PM) ac line-start motor. The earlier work of Chang and of Finch and Lawrenson on capacitor reluctance motors is extended. As far as possible, a common set of reference frame transformations for steady-state, transient, and asynchronous performance is also provided, permitting the use of all the theory developed for the analysis of the balanced polyphase PM motor. A new approximate technique is given for estimating the average asynchronous torque/speed curve from computed acceleration curves.

Abridgment of line-start induction motors

Many manufacturers of polyphase squirrelcage induction motors in the integral horsepower sizes have now added to their other products, a modified form of squirrelcage motor in which the starting current is reduced below that of the standard squirrelcage motor. The reduction in starting current is sufficient to warrant the power companies throughout this country to permit the starting of these motors directly across the line without the use of a starting compensator. This type of motor is now sold under a variety of trade names, such as line-start motors, auto-start motors, double-deck motors, double squirrelcage motors, high-reactance motors, etc.