Salient-pole Synchronous Motor Research Articles

Temperature Field Distribution and Thermal Stress Analysis of Pumped Storage Electric Motors

Abstract With the increasingly important role of pumped storage in energy systems, new and higher requirements have been put forward for the operation, safety, and economy of pumped storage power plants. The article takes a three-phase salient pole synchronous pumped storage motor as the research object, by using ANSYS finite element analysis software, a finite element model of a three-phase synchronous generator motor was established to analyze the internal temperature field distribution and thermal stress distribution of the motor. The results show that the higher temperature region of the entire system was concentrated at the winding, followed by the stator and rotor. Therefore, when optimizing the design of the motor in the future, the first step should be to start from the winding. The analysis of the thermal stress situation of the stator shows that the thermal stress and strain were mainly distributed at the inner diameter of the stator core, which was consistent with the distribution of the temperature field at the stator. The results of this study can provide theoretical guidance for the key maintenance areas and maintenance time of pumped storage power generation motors.

Control laws of a salient pole synchronous machine in a mine electric locomotive

Relevance. The need to find effective control of a traction synchronous motor with permanent magnets in a mining electric locomotive under conditions of limitation of current and voltage supplied to its windings from an autonomous power source. Aim. To choose a control law that ensures an increase in a mine electric locomotive mileage on one battery charge with its speed growth. Object. Control laws of a salient pole synchronous motor with permanent magnets of a mining electric locomotive; laws of current control along the transverse axis; control by the current minimum and control by minimizing the reactive power of a salient pole synchronous machine. Methods. Analysis of the state of the electric machine with different formation of control of an electric drive in the mine electric locomotive. The main limiting indicators of an electric machine with voltage and current limitation were considered. For each control law, the results of mathematical modeling are shown in graphical and tabular form. Results. The analysis of the current control law along the transverse axis demonstrates a significant increase in reactive power with increasing load. In an hourly mode of operation, the reactive power exceeds the active power spent on the movement of the electric locomotive. When limiting the current and voltage, the minimum current control allows you to increase the electromagnetic torque by 12.7% in hourly operation. The maximum engine speed is increased by 13%. The maximum power spent on the electric locomotive movement increases by 33%. Reactive power is reduced by 29%. With reactive power minimization, despite the decrease in the electromagnetic torque in the hourly mode of operation by 4.8%, the maximum possible engine speed increases by 53%, the power spent on the electric locomotive movement increases by 50%.

Mathematical model for salient-pole synchronous motor field-coil calculation and optimization

To optimize the parameters of the salient-pole synchronous machine field-coil and achieve specified technical and economic characteristics, an optimization problem with restrictions, which belongs to the class of nonlinear programming problems, was solved. Mathematical model for salient-pole synchronous motor field-coil calculation and optimization, an algorithm and a computer program were created. The mathematical model for calculation and optimization of salient-pole synchronous machine field-coil provides a possibility to design a single-row field-coil winding based on known dimensions under the following restrictions: the minimum distance between the coils of adjacent poles must not be less than the permissible value, the temperature of the coil above the ambient temperature must not be greater than the maximum permissible for the chosen insulation class of the value of the coil, according to the conditions of single-row coils manufacturing, conductor cross-section area should not be greater than the permissible value, and the ratio of the width of the conductor to its height should be within certain limits, the dimensions of the conductor should correspond to standard values. The optimization criterion (objective function) is the copper consumption or cost of the coil, the consumption or cost of pole core steel, power losses in the coil, the total cost of copper and pole steel, the total costs of machine manufacturing and its operation. The choice of the optimization criterion depends on the purpose of the machine and the requirements placed on it. In this problem, each of these criteria is a function of one variable - the height of the field-coil.

Method of calculation of the magnetic induction of the stator winding of a spiritual synchronous motor

This article discusses the calculation of the magnetic fields of the differential scattering of the stator, passing in the radial direction (penetrating the body of the rotor core), taking into account the saturation nonlinearities of the tooth zones of the magnetic circuit. The results of the method for calculating the magnetic permeability of the final values of the steel sections of the magnetic circuit in the stator and rotor of a salient-pole synchronous motor for its spatial harmonic fields in the air gap are presented.

Starting winding parameters influence on starting characteristics of salient-pole synchronous motor

The asynchronous method of starting a salient-pole synchronous motor (SPSM), its starting characteristics, which are the dependence of the current I of the stator and the electromagnetic moment M to the slip s at constant stator winding feed voltage U and frequency f have been analyzed. A mathematical model that considers magnetic and electrical asymmetry was designed. The magnetic asymmetry of the SPSM is cased by the salient-pole structure of the rotor, and the electric - due to the different number of windings along the longitudinal and transverse axes. To consider the magnetic and electrical asymmetry of SPMS carry out the following transformations: 1) replacing of the three-phase stator winding with two-phase, where the magnetic axis of one of the windings coincides with the longitudinal axis d, and the magnetic axis of the second winding - with the transverse axis q of the fixed coordinate of the orthogonal system dq; 2) the starting short-circuited winding is replaced by two windings: a longitudinal starting winding, the magnetic axis of which coincides with the d-axis, and a transverse starting winding, the magnetic axis of which coincides with the q-axis; 3) the movable rotor of the engine is considered stationary. The developed mathematical model showed that the starting properties of SPSM and the type of its starting characteristics depend on both: the parameters of the stator windings and the parameters of the rotor windings - the starting winding and the excitation windings. During the SPSM design process, the specified starting properties can be achieved by the variation of the starting winding parameters, which depend on the number of rods, sizes, and materials of rod and short-rings, as well as the size (width and height) of the slot groove. A computer program for calculating its starting characteristics with a given set of parameters for researching SPSM according to the described mathematical model was developed.

Run-Up Protection in High-Inertia Synchronous Motor Applications

High-power salient-pole synchronous motors utilized in high inertia compressor applications in the air separation industry usually exhibit long starting times. During long asynchronous starts, there is a high thermal load induced in the rotor and motor protection becomes more challenging. Long starts are typically defined as run up times that exceed the permissible locked rotor time. The physical and mechanical limits of these motors and their influence on repetitive starts and waiting times are presented. A protection scheme based on current-time characteristics (thermal limit curves) is commonly applied. A general explanation of thermal limit curves and the benefits as well as the limits of these curves is given, for example, the missing ability to display former heat impact and temperature distribution in different parts of the motor. An alternative time-speed-based protection approach is presented. The topic of consecutive starts is discussed along with a method to better utilize the motor thermal capacity. In addition, a procedure to obtain realistic rotor-temperature data from test-field runs and measured data are presented.

Insight to Enhancing the Performance of the Pole Drop Test for Detecting Field Winding Turn Faults in Salient Pole Synchronous Motors

The pole drop test is the most widely applied off-line test for detecting shorted turns in the field winding of salient pole synchronous motors. It is a simple test where the voltage drop (or inductance) of the poles are compared to detect the presence of shorted turns. Although it does not require special test equipment, false indications due to sensitivity problems are common. In this letter, the voltage and inductance distribution between the poles are analyzed under shorted field turn conditions. Some practical insight for enhancing the sensitivity and reliability of the pole drop test are given based on the qualitative analysis and experimental testing on a 30 kVA synchronous motor with shorted field turns. It is shown that the sensitivity of the test is significantly higher when the test is performed with the rotor inserted, which is not reported elsewhere. It is also shown that the reliability of the test can be improved by observing the voltage or inductance in poles adjacent to the pole suspected with shorted turns.

Research on External Fault of Salient Pole Synchronous Motor at Rated Load

The pumped storage power station is an inevitable product of the power system structure and power supply demand development to a certain stage, and it is a necessary management tool to ensure the safe and stable operation of the power system. Pumped storage power plants have the ability to improve and balance the load of the power system, which can improve the quality of power supply to the power grid and improve overall economic benefits. With the development of high-tech industries such as informatization and digitization and the improvement of people’s living standards, society has higher and higher requirements for pumped storage power stations. Pumped storage motor is a three-phase salient-pole synchronous motor used in pumped storage power stations. This paper simulates and analyzes the stator voltage, current and electromagnetic torque when single-phase grounding short circuit, inter-phase short circuit, and two-phase grounding short circuit occur in pumped-storage motors, and the law of change is obtained.

Analysis of electromagnetic force of damping winding in salient pole synchronous motor short circuit fault

In recent ten years, China’s pumped storage power station has developed rapidly. As the core component of pumped storage unit, salient pole synchronous motor is very important to study its abnormal operation. In this paper, taking salient pole synchronous motor as the research object, the mathematical expressions of magnetomotive force for single-phase short circuit to ground, phase to phase short circuit and two-phase short circuit to ground are derived respectively, and the mathematical law of magnetomotive force for short circuit fault of salient pole synchronous motor under generating condition is revealed. It provides a basis for fault diagnosis, related research and calculation of salient pole synchronous motor.

Analysis of short circuit electromagnetic force of salient pole synchronous motor winding

China’s pumped storage power station has a broad prospect, in which salient pole synchronous motor plays an important role. In this paper, the mathematical expression of electromagnetic force in the case of short circuit of the excitation winding of salient pole synchronous motor is derived, and the variation law of electromagnetic force density in the case of fault corresponding to the electromagnetic force of damping winding is calculated. The mathematical law of electromagnetic force in the case of short circuit fault of salient pole synchronous motor is revealed, which has practical reference significance.

Analysis of Energy Saving Effect of Large Double-speed Salient Pole Synchronous Motor in Renovation of Pumping Stations

The water levels influenced by seasons are varying, which needs a great variation of pumping head. The motor now used with complex speed equipment and high cost cannot satisfy the requirement. The paper takes the renovation and transformation of Song Long pumping station as an example, analyses the effect of using large double-speed salient pole synchronous motor. It offers a comparative analysis of the energy-saving benefit, which has three major evaluation indexes: device efficiency, unit energy loss and the benefits. The related research results can be referenced in the renovation and transformation of pumping station.

Starting Characteristics with or without Starting Circuit for Salient Pole Synchronous Motor

Starting Characteristics with or without Starting Circuit for Salient Pole Synchronous Motor

Airgap Flux-based Detection and Classification of Damper Bar and Field Winding Faults in Salient Pole Synchronous Motors

Recent cases of broken damper bars and shorted field winding turns in synchronous motors (SMs) have shown that rotor faults can degrade motor performance and lead to a forced outage of the motor and driven process. However, detection of SM rotor faults has not received much attention since SMs are not as common as induction motors. Detection of SM rotor faults is difficult, as the damper bar is active only under the starting or load transients, and shorted field winding turns result only in a slight increase in rotating asymmetry. SM rotor fault testing in the field mainly relies on visual inspection or off-line tests, and new test methods that can provide reliable detection of the faults without motor disassembly is highly desirable. In this article, new test methods for not only detecting, but also classifying the two types of SM rotor faults under motor standstill and starting are proposed. A finite element and experimental study on 1.1 MW and 30 kW salient pole SMs are provided to verify the proposed methods. It is shown that damper and field winding faults can be detected and classified with high sensitivity and reliability compared to conventional tests.

Comprehensive Monitoring of Field Winding Short Circuits for Salient Pole Synchronous Motors

An interturn insulation failure in the field winding of synchronous motors is a common problem that can lead to degradation in performance and accelerated wear of motor components. Existing offline tests for detecting this fault are known to be unreliable and inconvenient to perform, as they require motor disassembly. Online monitoring based on airgap flux monitoring has been proven to be successful, but could lack sensitivity for cases where the number of turns per pole is large. In addition, field winding turn shorts can be intermittent depending on the centrifugal force and could be unobservable at standstill or under an steady state operation. Therefore, monitoring of the turn faults under standstill and starting conditions with high sensitivity and without motor disassembly is desirable. In this paper, the detection of field winding short circuits for salient pole synchronous motors based on an airgap search coil under the starting transient, and new methods for standstill testing without motor disassembly are proposed. Two-dimensional finite element analysis and experimental testing on a 30-kW motor are given to verify the claims made. It is shown that the proposed set of tests can provide sensitive and reliable detection of field winding short circuits under standstill and starting conditions.

Experimental validation with field circuit by changing start voltage of salient pole synchronous motor

AbstractThis paper reports on the experimental validation characteristics of a salient pole synchronous motor with the starting field circuit in contact. The starting characteristics were experimentally evaluated at voltages of 100%, 75%, and 50% using a 1.5 kVA salient pole synchronous motor. The signal for pulling into step was applied to the field circuit by using the control module for all test conditions. The results confirmed the proper pulling into step at 100% of voltage, and the results of the tests at 50% and 75% of voltage revealed that the pulling into step under these conditions becomes stable at the suitable slip condition.

Airgap Search Coil-Based Detection of Damper Bar Failures in Salient Pole Synchronous Motors

Damper bars are often used in high output salient pole synchronous motor (SM) rotors for motor starting and stabilization of performance. Several cases of broken damper bars in the rotor of SMs that lead to motor starting failure and/or forced outage have recently been reported. However, detection of damper bar failures is difficult, since the damper bars are active only under the starting or load transients. Damper bar testing in the field currently relies on off-line visual inspection, and there is no means available for detecting failures on line. In this paper, a new method for detecting damper bar failures based on the analysis of airgap search coil measurements under the starting transient is proposed. Since airgap search coils are being increasingly installed in large SMs for detecting field winding short circuits, the proposed method can be implemented without additional hardware. The effectiveness of the proposed method is verified with two-dimensional finite element analysis and experimental testing on a custom-built 30 kW salient pole SM under controlled fault conditions. It is shown that the proposed method can provide reliable and sensitive detection of broken damper bars whenever the motor is started at low additional cost. The off-line single phase rotation test is also shown to provide reliable monitoring of damper bar condition.

Experimental Validation with Field Circuit by Changing Start Voltage of Salient Pole Synchronous Motor

Experimental Validation with Field Circuit by Changing Start Voltage of Salient Pole Synchronous Motor

STUDYING THE EFFECT OF AN ADDITIONAL ACTIVE RESISTANCE IN THE FIELD WINDING CIRCUIT ON STARTING CHARACTERISTICS OF SALIENT-POLE SYNCHRONOUS MOTORS

On the basis of the developed method for calculating steady-state asynchronous operation modes of salient-pole synchronous motors, a procedure of mathematical modelling of the starting characteristics is proposed. The problem of calculating the steady-state asynchronous mode is solved as a boundary value one for differential equations of motor circuit electrical equilibrium. Algebraization of the system of differential equations is carried out by approximating the equations of state using cubic spline functions on a grid of period nodes, taking into account the periodic law of variation of the coordinates. This results in the changeover from continual values to nodal ones. The starting static characteristics are calculated using the parameter continuation method. The study of the effect of the starting resistance value on the asynchronous characteristics of the motor relied on a mathematical model of the motor taking into consideration real field circuits, saturation and asymmetry of the magnetic path.

A Method of Determining the Equivalent Core Length of the Large Synchronous Motor With Radial Air Ducts

A method of getting the more accurate equivalent core length through 3-D electromagnetic finite element method (FEM) (3-D FEM) is presented in this paper. It is a matter of course that 2-D FEM is mostly used to evaluate the rotating machine performance instead of 3-D FEM. It takes 106 times longer to complete 3-D FEM than to complete 2-D FEM according to the simulation data in this paper. The motor has the radial air-cooling ducts in the stator. The use of radial air-cooling ducts has an effect on the electrical performance of its machine due to the fringing effect between ducts. The way to consider that effect is that the actual core length has to be replaced with the equivalent core length to reflect the magnetic circuit of 2-D perspective. However, there is 12% error of the root mean square no-load voltage between 2-D and 3-D FEM in 16 MVA salient pole synchronous motor. The cause of the error is the miscalculated equivalent core length in 2-D FEM. The purpose of this paper is to study the cause of the error through 3-D FEM to get the more accurate equivalent core length in 2-D FEM. Finally, Generator open circuit characteristic test is also carried out to verify the no-load voltage of 2-D and 3-D FEM.

A Study for Starting Characteristic Analysis Method of Salient Pole Synchronous Motors

Solid rotors can be adapted to synchronous motors of 5 MW and over in applications with high inertia loads. The eddy currents induced in the solid pole are used for starting of the motor and their paths are changed depending on the design of the rotor shape unlike the synchronous motors with damper windings or cages. In this paper, the starting characteristic of a 7 MW solid salient pole synchronous motor is analyzed by the combined methods for two and three-dimensional finite element models because a three-dimensional analysis to solve the problem is difficult due to the long solving time. The maximum difference between results of the combined method for two and three-dimensional finite element analysis and the factory test is less than 10%.