為了提高大型水輪發電機的運行可靠性，設計人員對電機的冷卻系統作了不少改進，基中包括線圈采用液態介質內冷系統等。蒸發冷卻技術已在中國數個電站的幾臺立式水輪發民機中得到應有和，并經歷了長時間的商業運行考驗。為了驗證這種新型冷卻系統的優越性，應對電機內的溫度場進行深入的分析。該文以有限元法計算了采用蒸發冷卻系統的大型水輪發電機定子三維溫度場，以包括導體、端部繞組及通風溝在內的定子半個齒距全軸向長度為計算域，并考慮蒸發冷卻的特點，建立了物理和數學模型。論文以李家峽電站一臺400MW蒸發冷卻發電機為實例，計算了不同工況下的定子溫度分布，計算結果與現場實測數據進行分析比交，驗證了計算方法的正確性。論文得出了一些有助于設計和運行的結論。

考慮水輪發電機端部結構的物點，計入材料的各向導性和非線性，以電路和磁路等效原理導出定子鐵芯疊片邊段和分瓣壓圈的等效電導率及磁導率。計算了一臺725MW水輪發電機在各種工況下的端部磁場，結果與實測值非常吻合，證明了所提出方法的正確性。計算了李家峽400MW水輪發電機在欠勵工況下的端部磁場，并與現在進相工況進行時的實測數據對比，結果滿足工程要求，為預測水輪發電機進相能力和充電空量提供了依據。

Small-xignal stability analysis methods based on an impendance criterion originat from the minor lop gain mehtod and are gradually utilized om twp-stage dc distributed power systems. In this paper, we conclude that the impedance criterion directly dependent on output impedance Z。(s) of the source subsystem and input impedance Zi(s) of the load subsystem is possible but gives and invorrect stability analysis for systems with a regulated source subsystem. Through introducing a mapped pure impedance of the load subsystems and the preliminary system, we develop a general three-step impedance criterion, with which a correct small-signal stability analysis can be guaranteed. regardless of the type of sorce subsystem. Furthermore, we introduce the application of the three-step impedance criterion in two small-signalstability analysis cases and utilize it in an example system to predict the sability shift process arising from the variation on the load resistance and input voltage value.

After more than 40 years theory research and industry paractice, evaporation-cooling technology has miade great breakthrough at the end of 20th centruy. On December Ist 1999. a 400MW evaporation-cooling hydro-generator was put to use in Chinese power system at lijiaxia power sation of Qinghai province. Industry experience shows that evaporation-cooling technology keeps the advantages of the old ones and overcome the main disadvantages of them. So it has many prospective applications in 21st century.

21世紀隨著國民經濟的快速發展，中國水力發電業將會有巨大的發展，將要安裝許多巨型機組。大工率、大尺寸、大重量是這些機組的物點，而為制造出這些機組，生產廠將面臨許多技術難題。本文簡述了國內水電設備制造業的現狀，存在的主要問題，生產這些巨型機組將遇到的技術難題等，文末提出了若干條建議。

Impedance character as well as relevant impedance criterion is important in thesmall-signal stability analysis of multi-sgage dc distributed power systems, where subsystems are integrated. At the same time, we usually approximately simplify a tightly controlled load-converter as constant power load. In this paper, we focus on the impedance character and impedance criterion in two-stage dc distributed system, which is in fact criterion in two-stage dc distributed system, which is in fact inter-dependent dynamical system with both interaction loop and many individual regulation loops. We verify that minor loop gain method can be directly extended to inter-dependent subsystems, while original impedance criterion cannot. Furthermore, we develop a substitutional stability analysis. With this substitutional impedance criterion, we discuss the influence of regulation loop gain, load resistance, input voltage and various duty-cycle ration on system small-signal stability. In additon, we analyze the impedance shift process of the imput impedance of load-converter and build the relationship between it and rgeulation loop gain. Negative rgsistor approximation of load-converter is only regarded reasonable when high regulation-loop gain is assumed and low-frequeney character of load-converter is considered. Simulation results illustrate the validity of the substitutional impedance criterion.

In order to reduce the vibration of the stator core in the large hydro-generators, the recent tendency is to stack the stator core at site for the hydro-generators with the diameter larger than ten meterws. Owing to the temperature difference between the core and frame of the stator, the frame will restrain the expansion of the core, which will lead to buckling of the stator core in case of high-stiffened frame. But in order to prevent forom the eletrmagnetic vibration the stator frame will be required to have an appropriate supporting stiffness for the stator core. The investigation of the thermal deformation in the generator must be based on comprebensicve analysis of the temperature distrbution within the begnerator under different operation conditions. Inthis paper a method by FEM for calculation of the 3D thermal field within the benerator is applied. Based on the results of the thermal field calculation, the thermal deformation of the stator core and the frame can be calculated. As an example, the thermal field and deformation of a 400MW evaporating cooled generator have been calculated. The comparison of the calculated results with those measured at site proves that the applied method in this paper has apprpiate precision.