Improved Damper Cage Design for Salient-Pole Synchronous Generators

Abstract

Abstract-The benefits of implementing a damper winding in salient-pole, synchronous generators are widely known and well consolidated. It is also well known that such a winding incurs extra losses in the machine due to a number of reasons. In order to improve the overall efficiency and performance of classical salientpole, wound field, synchronous generators that employ the traditional damper cage, an improved amortisseur winding topology that reduces the inherent loss is proposed and investigated in this paper. This is essential in order to meet modern power quality requirements and to improve the overall performance of such 'classical' machines. The new topology addresses the requirements for lower loss components without compromising the acceptable values of the output voltage total harmonic distortion and achieves this by having a modulated damper bar pitch. As vessel for studying the proposed concept, a 4MVA, salient-pole, synchronous generator is considered. A finite element model of this machine is first built and then validated against experimental results. The validated model is then used to investigate the proposed concept with an optimal solution being achieved via the implementation of a genetic algorithm optimization tool. Finally, the performance of the optimised machine is compared to the original design both at steady state and transient operating conditions.

Finite Element Computation of Transient Parameters of a Salient-Pole Synchronous Machine

“…The mean values of the subtransient and transient reactances in each computation time instants, shown in Table 3, are the subtransient and transient reactance parameters of the prototype computed by the presented method. A comparison of the prototype experimental values and the transient parameters calculated using both the proposed and conventional short-circuit methods [3] is shown in Table 4. The experimental value of the prototype is provided by the Power System Dynamic Simulation Laboratory where the presented prototype is installed and applied for dynamic simulation experiments.…”

“…The inductances are calculated with the method presented in Section 3. 3 The flux distributions at the no-load condition before the short-circuit in Figure 7a and at the transient condition after the short-circuit in Figure 7b are vastly different. The variation in the flux distribution can lead to variation in the inductances of the SPSM, including leakage inductances; therefore, the variation should be investigated and considered in the computation.…”

“…In hydroelectric plants, SPSMs have been applied as generators since the nineteenth century. The SPSM is also preferred as the type of generator used in ships [3]. In traction drive, mine hoist, and marine propulsion, SPSMs are commonly employed as drive motors [4].…”

Analysis, Modeling, and Design Considerations for the Excitation Systems of Synchronous Generators

“…contains all the equivalent Winding Functions (WFs) NEi [9,10] of the machine phases, whereas µE(β,γ) is the equivalent magnetic permeability function, whose expression is given in [10] and [11]. It is important to note that the equivalent functions mentioned above contain all the information necessary for the phase self-inductance calculation, namely the anisotropies of the machine, the position of the active sides of the coil, the number of conductors per coil, etc.…”

“…Considering the diode rectifier of the brushless excitation system analyzed in this paper, then the calculated value is ΔVmg=32.3V, which is about 30% of the DC voltage needed by the rotor of the main SG when operating at full-load condition. Having determined ΔVmg, then this can be used to recalculate the exciter output AC voltage VLL_NEW needed to compensate for it, as given in (11), where the classical rectifiers' theory is utilized to transform from DC to AC quantities [4]. The calculated inductance and the updated VLL_NEW can then be used in (5) to re-evaluate µ.…”