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The aim of this article is to develop a rotor reconstruction method for the V‐shaped interior permanent magnet (IPM) machine so that the subdomain method to analytically calculate the air‐gap flux density can be applied. With the proposed method, the V‐shaped IPM rotor with rectangular magnets, magnetic barriers, and saturated iron bridges can be transformed into a U‐shaped equivalent analytical model. The geometry and material parameters of the magnets in the equivalent U‐shaped model can be determined according to the flux equivalence in the air‐gap of the motor. Then using the subdomain method on the U‐shaped equivalent rotor, the static magnetic field problem can be solved and the flux density distribution in the air‐gap be obtained. The validity of this method and accuracy of the solution is verified by the finite element method with case studies. Compared with existing methods, the improved subdomain method has higher accuracy in calculating flux density including radial and tangential components. The presented rotor reconstruction method is not only limited to single‐layer V‐shaped rotor, it can also be applied to other IPM rotors with more complex structures. It is valuable in the design, optimisation of IPM motors, and even development of new rotor topology. [ABSTRACT FROM AUTHOR]

In this article, a hybrid analytical model for a quasi‐regular polygon rotor (QPR) is proposed. It mainly uses the subdomain method and conformal mapping to solve a non‐circular boundary in the QPR. Firstly, the subdomain method combined with an equivalent surface current method is used to calculate the air‐gap magnetic field considering a slotted stator with a circular rotor. Secondly, by segmenting the non‐circular boundary in the QPR, the complex relative air‐gap permeance of the QPR can be calculated using the conformal mapping. Thirdly, this complex relative air‐gap permeance modifies the air‐gap magnetic field calculated in the first step to obtain the actual magnetic field distributions. Consequently, no‐load and loaded air‐gap flux densities, back‐electromotive force and torque can be obtained. A 12‐pole/3‐phase permanent magnet motor is modelled using the proposed hybrid analytical model, which is validated by finite‐element analysis and experiment. This proposed hybrid analytical model presents a new way of processing the QPR. Its calculation speed is nearly 50 times faster than the finite‐element analysis, which is of great help to the initial design and optimisation of machines with QPRs. [ABSTRACT FROM AUTHOR]

The dual‐excited synchronous condenser (DESC) has two field windings whose axes are located at direct and quadrature axes respectively. The DESC has more capacity of absorbing reactive power than that of the traditional synchronous condenser (TSC). However, the q‐axis field winding distributed on the d‐axis magnetic pole surface can decrease the magnetic circuit area of the rotor core of DESC, thus it may result in the increase of the total harmonic distortion (THD) of the magnetic field and the oversaturation of the rotor magnetic circuit. In order to obtain better electromagnetic characteristics of DESC, a q‐axis field winding structure is proposed by optimising the number of slots, slot pitch and slot dimensions. The influences of the number and pitch of slot in q‐axis on the air‐gap radial flux density and THD of DESC are studied under the d‐, q‐ and dual‐axis excitation modes. The dimensions of the q‐axis slots are optimised by combining the time‐stepping finite element method and Taguchi method, and the optimal structure of q‐axis field winding is obtained. A 10‐kVar DESC is developed to verify the simulation results. This study provides theoretical basis for the design and manufacture of the DESC. [ABSTRACT FROM AUTHOR]

To investigate the effect of initial dynamic eccentricity on the rotor winding turn‐to‐turn short circuit (RWISC) in a large synchronous condenser, this paper uses the study object of a 300 MVar dual water intercooler condenser. Firstly, the air gap flux density characteristics, unbalanced magnetic pull (UMP) and stator circulating current of the condenser under single and compound faults are derived theoretically. Then, a phase‐modulated field‐circuit coupling model is constructed using Anosoft software. It is used to simulate and analyse the condenser. Finally, the operation of the condenser was simulated with the SDF‐9 experimental setup, and the correctness of the theoretical derivation and simulation analysis was verified. The results show that the initial dynamic eccentricity of the condenser has a cutting effect on the fault characteristics generated by the RWISC. The 2nd harmonic of air gap flux density and stator circulating current and the fundamental wave of UMP decrease and increase with eccentricity. This study can provide theoretical guidance to eliminate disturbing factors to improve the accuracy of RWISC diagnosis in large synchronous condensers. [ABSTRACT FROM AUTHOR]

Unbalanced magnetic pull (UMP) occurred due to the uneven distribution of magnetic flux around the airgap, which can be caused by the existence of rotor eccentricity in the machines. Here, a UMP damping coefficient is introduced to explain the UMP damping effect from the counteracting flux produced by a parallel-connected cage rotor. An empirical method is proposed to calculate the UMP using the damping coefficient and an analytical model. Using the proposed method, a four-pole and eight-pole squirrel cage induction machine with static eccentricity are investigated, which uses inputs from both finite element analysis and experimental work. Then, the UMP calculation for a dynamic eccentricity with the extracted parameters is done to verify the empirical method. A slip control method is described which uses a UMP/torque ratio to find the operating slip with the lowest UMP. Comparisons between results with and without slip control are made on both induction machines. It shows that great reduction in UMP can be achieved when the machine is lightly loaded. [ABSTRACT FROM AUTHOR]