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  • Users: Yuma
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  1. Yuma

    DC circuit breaker capacity vs time constant

    Hello to all, and sorry for not having answered before, I was on holidays. FacEngrPE: yes, I agree with what you say, but I am still wondering how to assess (if possible) the validity of a breaker for a higher time constant. According to the nameplate, the breaker's rating in DC is 250 V, 50...
  2. Yuma

    DC circuit breaker capacity vs time constant

    Thanks Gr8blu!
  3. Yuma

    DC circuit breaker capacity vs time constant

    Dear all, I have a question on the breaking capacity of a DC circuit breaker. If a DC circuit breaker is able to break 50 kA with a time constant of 15 ms, how do you calculate the new breaking capacity for other time constant, say 45 ms for example? Searching the web I came across the...
  4. Yuma

    Rotor jumpering

    Hi Electricpete, When you say "jumpering 2 poles 180 mechanical degrees apart. But that means losing two poles of the same magnetic polarity", it seems to me that it depends whether the number of pairs of poles is odd or even. Do you agree? Or am I missing something?
  5. Yuma

    Lorentz Force Calculation - Busbar

    Thanks a lot Desertfox! A star for you [thumbsup2]
  6. Yuma

    Lorentz Force Calculation - Busbar

    Dear Desertfox, The link you sent seems very interesting to me, but alas, no longer works. I have tried Archive.org and I have been able to download all of the chapters except for chapter 4, which is about short-circuit currents. Would you be so kind of posting it? Thanks
  7. Yuma

    B-H curve of 26 NiCrMoV 14 5 material

    Dear all, I am using FEMM for doing some calculations and I am looking for the B-H curve of 26 NiCrMoV 14 5, a material that is commonly used for generator rotors. I found that it is equivalent to ASTM A470. On the Internet it is easy to find the mechanical properties, but not the magnetic...
  8. Yuma

    temp limits for new generator

    Thanks Scotty and Muthu. Yes, you are right, Class F insulation running at Class B temperatures has been a common requirement for other generators we have purchased. Kind regards
  9. Yuma

    temp limits for new generator

    Dear all; If you had to purchase a new generator, - 400 MW, H2 inner cooled - what is the maximum temperature that you would expect to measure at full load? For the windings, assuming class F, in theory you could accept 155 ºC - 15 ºC for hot spot tolerance = 140 ºC... but I have never seen...
  10. Yuma

    looking for efficiency curves for AvK generator

    Thanks to both of you, Warross: you are right, the efficiency of the generator is not that important; the reason I am looking for this data is that it is required by the local regulation. Catserveng: thanks for the data! By the way, a colleague of mine has just found what appears to be the...
  11. Yuma

    looking for efficiency curves for AvK generator

    Dear all, I am looking for the efficiency curves of an AvK generator, coupled to a 339 CAT engine. The nameplate data: Type: DIB130F/6D Year: 1976 Voltage: 380/220 Current: 1750 A Power: 1150 kVA Cos phi: 0,8 Speed: 1000 rpm Frequency: 50 Hz AvK no longer exist, they eventually became Cummins...
  12. Yuma

    rewinding effects

    I suggest going to FSNL / sync idle and compare the vibrations with and without excitation, before paralleling.
  13. Yuma

    calculation method of loop test of core stator frum

    Hi, You can find the details in the following books: Electrical Insulation for Rotating Machines, by G.Stone et al, section 17.2.2 Operation and Maintenance of Large Turbogenerators, by Klempner & Kerszenbaum, section 11.2 Regards
  14. Yuma

    Books for Electrical Machinery & transient Stability

    'Power Systems Stability and Control' by Mr. Prahba Kundur is a very good reference for me. Regards
  15. Yuma

    CT typical resistance value

    Afroeeng: Thanks, unfortunately I don't have the data to make those calculations. Mgtrp: That is more or less what I was thinking. I'll assume 0,2 ohm and probably I'm still on the safe side. Many thanks.
  16. Yuma

    CT typical resistance value

    Hi all, Can anybody suggest typical values for the secondary resistance of these CTs? 50/1 A 15VA Cl. 1 50/1 A 10VA 5P20 These are fairly old CTs and I can't find the documentation from the manufacturer. Nor can I measure it because the plant cannot be stopped right now. My guess is...
  17. Yuma

    stationary blade rings of the generator blower

    Dear all, We have several Westinghouse generators, type 2-102x202, 370 MVA, H2 inner cooled, made in the '70s and the 80's. Siemens has recently issued a Product Bulletin "PB2-10-0012-GN-EN01" in which they recommend to perform NDE on the stationary blade rings of the generator blower. This...
  18. Yuma

    Reactive power regulation on the island power plants

    Hi Slava, We don't have capacitors in our islands. All of our generators are cos phi=0,8, and are not run in cos phi control mode, but in voltage control mode. Hope it helps.
  19. Yuma

    concave-convex wedges for generators

    Thanks Byrdj, I wasn't aware of that document. It sounds strange to me that the idea was patented in 1992 and Alstom claims to have installed it in "hundreds of generators" yet I have seen a lot of generators manufactured by Alstom during the last 20 years and this is the first time that I come...
  20. Yuma

    concave-convex wedges for generators

    Those of you who own generators have probably faced the wedges problem. I am talking about the 'radial' wedges that lock the coils into the slot. The tightness of these wedges has to be periodically checked and, if the OEM finds some of them to be loose, they reccomend to partially or totally...

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