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Faults in Induction and Synchronous Motors
Published in Hamid A. Toliyat, Subhasis Nandi, Seungdeog Choi, Homayoun Meshgin-Kelk, Electric Machines, 2017
To produce torque in synchronous machines, the rotor must be turning at synchronous speed, which is the speed of the stator field. At any other speed, the rotating field of stator poles will not be synchronized with rotor poles, but first attracts, and then repels them. This condition produces no average torque and the machine will not start. Using a direct current (DC) motor or a damper winding, the machine can be brought near to the synchronous speed. Damper windings, as shown in Figure 2.5, consist of heavy copper bars, with the two ends shorted together, installed in rotor slots. The currents induced in the bars interact by the rotating air-gap field and produces torque. In other words, the machine is started as an induction motor [33]. The field winding is excited by a direct current when the machine is brought up to the synchronous speed. When the load is suddenly changed, an oscillatory motion will be superimposed on the normal synchronous rotation of the shaft. The damper winding helps damp out these oscillations.
Electric Machines and Power Systems
Published in Mohd Hasan Ali, Wind Energy Systems, 2017
The salient-pole construction is used in low-speed AC generators (e.g., hydroturbine generators) and also in synchronous motors. This type of machine usually has a large number of poles for low-speed operation and a large diameter-to-length ratio. The field coils are wound on the bodies of projecting poles. A damper winding (which is a partial squirrel-cage winding) is usually fitted into slots at the pole surface for synchronous motor starting and for improving the stability of the machine.
Modeling and Parameter Identification of Electric Machines
Published in Ali Emadi, Handbook of Automotive Power Electronics and Motor Drives, 2017
Ali Keyhani, Wenzhe Lu, Bogdan Proca
For on-line operation case, especially under high load, the losses become significant. There are no windings on the rotor of SRMs. But similar to synchronous machines, there will be circulating currents flowing in the rotor body, making it work as a damper winding. Considering this, the model structure may be modified as shown in Figure 22.42, with Rd and Ld added to represent the losses on the rotor.
Harmonic Electromagnetic Torque Analysis of Turbo-Generators by a Novel Lumped Magnetic Parameter Method and Finite Element Method
Published in Electric Power Components and Systems, 2021
Pin Lv, Xiaojie Wu, Xunwen Su, Ying Yang, Xianhui Zhu, Peng Lin
In this paper, firstly based on the symmetrical method [23–25], and the relationship between the electromagnetic torque and the electromagnetic power, the concrete derivation procedure for the new lumped magnetic parameter method (NLMPM) is introduced [26]. In the positive and negative sequence circuit, the lumped magnetic parameters employed by NLMPM are given explicitly. Then, by the NLMPM, the effect of damper winding on the second harmonic component of the electromagnetic torque is discussed, containing the existence of damper winding and the material alteration of damper winding. The two-dimensional finite element models of a 1400MVA and a 30kVA turbo-generator are established. The experimental data and finite element simulation data for no load characteristics and short circuit characteristics are compared and they fully test the effectiveness of finite element models. Through the comparison of the result of the NLMPM and the FEM, the effectiveness of the NLMPM is verified. The error between the two methods is researched. At last, the FEM is applied to investigate the effect of damper winding on second harmonic electromagnetic torque of super-large and middle-size turbo-generator. The conclusions achieved by the NLMPM and the FEM show remarkable consistency. The theoretical NLMPM introduced in this paper can accurately help detect the harmonic electromagnetic torque vibration according to the lumped magnetic parameters. Although the effect of damper winding is stated before, this paper presents a new method to analyze the effect of damper winding from a totally new perspective.
Linear inverted pendulum control based on improved ADRC
Published in Systems Science & Control Engineering, 2019
Bingyou Liu, Jinwen Hong, Lichao Wang
A simplified model of the AC servo motor is obtained on the basis of the following assumptions on the inside part of the motor: (1) Stator winding has a three-phase symmetrical mechanism, and the three phases have a Y-shaped distribution in space and are mutually different by 120°. (2) The saturation and associated losses of the stator core and the rotor core are excluded. (3) A no-damper-winding on the rotor exists, i.e. the permanent magnet does not have a damping effect. (4) The air-gap magnetic field generated by the stator winding is sinusoidal, but harmonics is not considered. (5) The saturation and related losses of the stator core and the rotor core are both ignored. (6) With regard to the effect of magnetic saturation, the magnetic circuit in space is linear. The dynamic equation of motion is obtained as follows: where is the electromagnetic torque generated by the motor, is the load torque generated by the motor, is the friction coefficient of the motor, is the angular position of the motor rotor, and is the moment of inertia of the AC servo motor. The dynamic characteristic structure is shown in Figure 2, represents torque current.
An energy-based analysis of reduced-order models of (networked) synchronous machines
Published in Mathematical and Computer Modelling of Dynamical Systems, 2019
T. W. Stegink, C. De Persis, A. J. Van Der Schaft
As energy is dissipated in the resistance of the rotor windings, the currents maintaining constant rotor flux linkages decay with time allowing flux to enter the windings. As for typical generators the rotor -damper winding resistances are the largest, the -damper currents are the first to decay, allowing the armature flux to enter the rotor pole face. However, it is still forced out of the field winding and the -damper winding itself, see Figure 2(b). Then, the generator is said to be in the transient state.