-------- In message <[email protected]>, Charles Steinmetz writes:
>The insides of mains alternators are almost entirely metal -- tons and >tons of copper tubing, and the casings and rotor shaft are steel. And >the alternators must operate at a relative humidity of absolute zero. This is close to to being "not even wrong". There is no requirement for "a relative humidity of absolute zero", which is theoretically impossible if there is any iron around. There are however stringent requirements for non-corrosion, dielectric potential, cooling, corona behaviour etc. etc. Cooling the stator is a no-brainer, it is almost always water-cooled. If they could afford to use helium to cool the rotor, they would jump on it instantly, but the cost is prohibitive at their leakage rates. Pure water would also be workable, but its high density means it cannot be used to cool the rotor without a serious hit to efficiency. Next down the line is hydrogen, which comes with a shitload of issues. Apart from all the obvious issues, lube-oil degradation, polymer degradation, fire-risk, risk of explosion, health-risk etc. hydrogen has "interesting" solubility in metals. If you want to purify hydrogen, you press it trhough a filter consisting of a solid slab of palladium, and that takes a lot less pressure than you would expect. For iron in particular, hydrogen means embrittlement, so a major focus in rotor design is to keep the hydrogen away from the iron. If you Google "generator hydrogen seal" and and you will find little love for hydrogen cooling. In 1993 Siemens put the first 170MVA air-cooled generator optimized by computer simulations of the flow-fields and since then the hydrogen cooling has been confined to an ever-decreasing top tier of name-plate power. Today fan cooling will take you to approx 400MVA and pressured air cooling will take you to about 600MVA. Above that, you are, almost by definition, in a nuclear power plant, and all problems from hydrogen cooling of your single huge generator pale in comparison to having a handful of smaller generators in parallel. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
