On Permeance Modeling of Large Hydrogenerators With Application to Voltage Harmonics Prediction

Abstract

In this paper, a permeance model that can be employed to estimate the no-load damper current loss and voltage waveform harmonics in large hydrogenerators is presented. The importance of modeling the damper magnetomotive force and inductances correctly is emphasized, and detailed descriptions are presented. The computed harmonics are compared with values obtained from time-stepped finite-element calculations and measured data. The results are in good agreement. The influence of pole-topole damper bar connections, and of the number of damper bars on the voltage waveform, is explained.

The rotating field method applied to damper loss calculation in large hydrogenerators

“…Hence, an inductance modeling according to (9) and (10) provides a physically sound yet simple representation of mutual damper loop couplings.…”

“…The derivation of the terminal voltage waveform from the air-gap flux density is described in [9] and is left out here for brevity. Fig.…”

“…Compared to rotating field models presented previously, we Φ The research presented was carried out as a part pf "Swedish also introduce a simplified managing of the mutual inductances in the damper circuit as well as modified damper MMF functions that better fit the actual air-gap flux created by the damper reaction. A more detailed description of these modeling aspects can be found in [9]. In the last part of the paper, we give examples of the damper current and loss prediction accuracy that can be expected for balanced and unbalanced load conditions.…”

Analytical calculation of damper winding losses in large hydrogenerators

“…ANALYTICAL MODEL The radial flux density g B in the air-gap of a salient-pole synchronous machine can be expressed as the product of a MMF function M and an air-gap permeance function Λ [6] ( , ) ( , ) ( , ) The waveform of air-gap flux density can be obtained by using the permeance model, which contains harmonic components. These harmonic waves travel with different liner speeds with respect to the rotor, and induce EMF and currents in the damper bars.…”

Modelling and experimental validation of internal short‐circuit fault in salient‐pole synchronous machines using numerical gap function including stator and rotor core saturation

“…According to some authors, the small air-gap width is a necessary condition for the WFT to give accurate results [16]. However, some authors have proposed strategies for extending WFT to salient-pole machines with strongly non-uniform air gap [17][18][19][20]. One common deficiency found in these attempts is that no clear and univocal procedure is defined in them for numerically and accurately identifying the permeance function for a generic air-gap topology.…”