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  • Users: Yuma
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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. Yuma

    locating a shorted turn in field winding

    Dear all, Are you aware of a method of locating a shorted turn in the field winding of a turbogenerator? I don't mean to tell whether there is a shorted turn or not, but to physically locate it so you know which retaining ring you shold dismantle in order to fix it. I remember an old timer...
  9. Yuma

    MAVR manual

    Dear all, Does anybody have the manual of the MAVR automatic voltage regulator made by Brush? Thanks in advance
  10. Yuma

    generator core repair alternatives

    Dear all, We are in the process of repairing the core of a salient pole generator. This core has a bad hot spot that shorts some of the laminations. The shop offers two alternatives to do the repair: option 1 - reuse the same core laminations, just relocating them in order to distribute the...
  11. Yuma

    mothballing a generator

    Dear all, We are thinking of mothballing a generator and as far as I know, you can use dry air, nitrogen or carbon dioxide for that. Can anybody comment on the pros and cons of the three methods? Is there any difference if the generator is water cooled or hydrogen cooled?
  12. Yuma

    Partial Discharges in a generator

    We have open a hydrogen-cooled 350 MW generator for inspection. To gain access to the basket winding, we have to remove an inner shield which is made of glass fiber and whose purpose is to conduct the flow of hydrogen. This shield is rather close to the basket winding, only a few centimetres of...
  13. Yuma

    RADSS manual

    Hi to all: Does anybody know how to find the manual of the old RADSS differential protection from ASEA? I have been looking for it at ABB's site but found nothing. Regards
  14. Yuma

    opening GE Comtrade

    Dear all; I have some Comtrade files downloaded from G60 type GE relays, that can be open using Enervista (GE) software. But I'd like to open them with Display Station 32, which gives more possibilities of doing some math with channels, harmonics, and the like. Unfortunately, DS32 seems to...
  15. Yuma

    Hi-Pot voltage levels for generator rotors

    Dear all; What do you think are the adequate voltage levels for Hi-Pot testing a generator rotor during an overhaul? I have been checking IEEE, IEC and EPRI but can´t find any document where it states clearly the voltage levels (either AC or DC) for rotors during a maintenance. Regards
  16. Yuma

    grounded battery system

    Could anybody please explain what is the effect of having a ground in either the positive or negative wire of a battery system, to the turbine control system? I've heard that maybe the control system gets some digital inputs wrong, i.e.; 1 instead of 0, or vice versa.... Thanks
  17. Yuma

    shaft voltage relay

    Hello to all; I'm looking for a protection relay that detects shaft current in a generator. I only know of the ABB RARIC relay. Does anybody know any other system? Thanks
  18. Yuma

    Diode failure by bad sync

    Hello to all; Talking about a turbogenerator with rotating diodes exciter, is it normal to have a diode failure condition because of bad paralleling to the network? If so, can you tell me why? Thanks

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