Short-circuited Rotor Winding Research Articles

Исследование технологии изготовления литых медных короткозамкнутых обмоток роторов асинхронных тяговых двигателей

The article focuses on the manufacturing process of cast copper short-circuited rotor windings of asynchronous traction motors. The basic technology developed at the Scientific Research Institute of Explosion-Proof and Mine Electrical Equipment with Pilot Production (NIIVE), Donetsk, allows the production of energy-efficient explosionproof asynchronous motors for driving mining machines and is focused on the use of only domestic materials and technological equipment. During the research, the process of preparing a copper liquid melt with a given electrical conductivity (copper melting technology) was studied, the possibility of manufacturing cast copper short-circuited rotor windings of asynchronous traction motors by vibration gravity was confirmed, the conditions for intensifying the mold filling process and solidification of the copper casting of the rotor (copper casting technology) were analyzed. The article presents the main results of technological research that can be used as initial data for the development of industrial casting technology for copper short-circuited rotor windings of AD914U1 type asynchronous traction motors.

Spiral vector modeling of brushless doubly-fed induction machines with short-circuited rotor windings

A unified spiral vector model is presented that can be used to assist the finite element method-based performance analysis of brushless doubly-fed induction machines with various short-circuited rotor windings. Specifically, magnet-free brushless doubly-fed induction machines working in doubly-fed or singly-fed synchronous mode are investigated. A dynamic model in spiral vector notation is developed, based on which the torque-angle and power-angle characteristics are derived. It is shown that the investigated brushless machines are equivalent to a traditional non-salient-pole synchronous machine with brushes. By introducing a conversion factor, they can also be analyzed with methods similar to the conventional phasor theory. A comparison is made between the brushless doubly-fed induction machine and non-salient-pole wound-field synchronous machine with brushes, revealing that the performance of the brushless machine degrades faster when the laminated core is saturated. A scaled-down prototype is tested to validate the effectiveness of the theoretical analysis.

Analytical analysis and performance characterization of brushless doubly fed induction machines based on general air-gap field modulation theory

Air-gap magnetic field modulation has been widely observed in electric machines. In this study, we present an analytical analysis and performance characterization of brushless doubly fed induction machines (BDFIMs) fed by two independent converters from the perspective of air-gap field modulation. The spiral-loop winding is studied in detail as an example to show the generalized workflow that can also be used to analyze other short-circuited rotor winding types, such as nested-loop and multiphase double-layer windings. Magnetic field conversion factors are introduced to characterize the modulation behavior of special rotor windings and facilitate their comparison in terms of cross-coupling capability, average torque, and harmonic content of the air-gap flux density waveforms. The stator magnetomotive force (MMF), rotor MMF, and resultant air-gap MMF are considered, based on which the closed-form inductance formulas are derived, and the torque equation is obtained along with the optimal current angle for maximum torque operation by using the virtual work principle. The design equations are then developed for the initial sizing and geometry scaling of the BDFIMs. Transient finite element analysis and experimental measurements are performed to validate the analysis.

Brushless Doubly Fed Machine Magnetic Field Distribution Characteristics and Their Impact on the Analysis and Design

This paper contributes to the characterisation of the brushless doubly fed induction machine (BDFIM), which is attractive as a variable speed generator in applications (off-shore wind turbine) with minimum maintenance requirements. The BDFIM has two three-phase stator windings of different pole numbers housed within the same stator slots and a short-circuited rotor winding capable of coupling fields of different pole numbers. The stator windings and rotor winding create a magnetic field distribution with a range of characteristics different to those of conventional induction machines. This paper presents an analysis to identify the field characteristics and discusses their impact on the analysis and design of the BDFIM. The characteristics are determined from an analysis of the sum of two rotating sinusoidal field waveforms and confirmed by comparison with time-stepping finite element results and measured magnetic flux density data.

Asynchronous slip-ring motor synchronized with permanent magnets

Abstract The electric LSPMSM motor presented in the paper differs from standard induction motor by rotor design. The insulated start-up winding is located in slots along the rotor circumference. The winding ends are connected to the slip-rings. The rotor core contains permanent magnets. The electromechanical characteristics for synchronous operation were calculated, as were the start-up characteristics for operation with a short-circuited rotor winding. Two model motors were used for the calculations, the V-shaped Permanent Magnet (VPM) – Fig. 3, and the Linear Permanent Magnet (IPM) – Fig. 4, both rated at 14.5 kW. The advantages of the investigated motor are demonstrated in the conclusions.

Excitation system of asynchronized turbogenerators

In contrast to conventional synchronous turbogenerators, an asynchronized turbogenerator can operate for a long time with a disabled excitation system and short-circuited longitudinal-lateral rotor windings, which increases substantially the operational reliability. The requirements on the power and information equipment of the excitation system with respect to redundancy are also less strict. Computer simulation of emergency conditions in an asynchronized turbogenerator has made it possible to substantiate the requirements on the speed of response to current reversal in the excitation system and to recommend an algorithm for protection performance upon transition of the turbogenerator to the standby mode.

Cascaded harmonic synchronous machine

In a number of applications of generating and motoring, a low shaft speed is required. The usual way of providing this low speed is either through large diameter multipole machines or through high-speed machines in conjunction with a gearbox. A novel machine has been designed which can interface the mains to a low-speed shaft without the necessity for a large number of poles. The principle of operation is based on a stationary DC magnetic field, a short-circuited rotor winding and a stator winding connected to the supply through a set of filters. The rotation of the rotor causes circulation of harmonic currents in the stator. The filters are designed to allow these circulations, but to divert the 50 Hz current into the mains. This effect provides a speed gearing, the level of which depends on the number of harmonics permitted to circulate. The principle can be applied to a single or 3-phase design. The operational characteristics are those of a synchronous machine possessing a distinct number of synchronous speeds.

Inductances of a Portion of the Armature Winding of Synchronous Machines

The main and leakage inductances are found from the flux linkages with the short-circuited part of the armature winding. The mutual inductances between the short-circuited part of the armature winding and the remaining part of the armature and rotor windings are proportional to the main inductance. A synchronous machine with a single phase-to-ground fault embracing a number of turns, Nf, can be regarded as an imaginary symmetrical machine having the armature winding with Nf turns in each phase and the same rotor construction as the actual machine. With such a provision, the synchronous and subtransient inductances of a part of the armature winding can be determined by the general theory of a synchronous machine. The damping of harmonic fluxes by currents in the short-circuited rotor winding is taken into consideration by the calculation of the subtransient inductances. The measurements of the subtransient reactances of portions of the armature winding have been performed on a synchronous machine. The calculated subtransient inductances deviate from the measured values; however, they can be used for the internal fault calculations within the permissible engineering accuracy.

Transient conditions in asynchronous induction machines and their relation to control problems

This paper discusses a number of transient conditions existing in asynchronous machines immediately after certain changes in the circuit connections are made. The advisability of considering these conditions in connection with the control layout for the purpose of eliminating bad effects caused thereby, is pointed out. The principal subjects considered are undesirable peak currents, which may be caused by the damping effect of the short-circuited rotor windings and the over-voltages, which are obtained with certain control arrangements.

Transient Conditions in Asynchronous Induction Machines and their Relation to Control Problems

This paper discusses a number of transient conditions existing in asynchronous machines immediately after certain changes in the circuit connections are made. The advisability of considering these conditions in connection with the control layout for the purpose of eliminating bad effects caused thereby, is pointed out. The principal subjects considered are undesirable peak currents, which may be caused by the damping effect of the short-circuited rotor windings and the over-voltages, which are obtained with certain control arrangements.