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  • Users: Rodmcm
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  1. Rodmcm

    60Vdc to 42V DC at 10A

    I have a regulated power supply 60VDC at 10A which I need to reduce to 42VDC Can anyone please point me in the right direction. I know about 3 term regulators but most have a limited current rating
  2. Rodmcm

    500 RPM 8000 kW hydro generator dimensions

    Hi Would anyone be able to share the dimensions of an 7 or 8MW 500rpm (12p 50HZ) horizontal synch generator
  3. Rodmcm

    Load Shedding ripple control low pass filter

    Would anyone know of a good source of commercially available low pass filters to reject 475HZ ripple frequency into 230AC 50HZ 60A loads? The ripple frequency is upsetting LEDs over a wide range of households
  4. Rodmcm

    Closed Loop Stepper Motor Control

    Perhaps not the place for this question but I cant find the answers anywhere! Small closed loop controllers such as the CL57T and LCDA257S allow settings from 800 to 51,200 pulses/rev from the encoders they connect to. There is only two encoder connections on these modules. Most of the small...
  5. Rodmcm

    Earthfaults, Delta Connections, and man safety

    If you look at many generation plant connections from MV to HV then the MV (say 11kV) bus is often unearthed until the generator synchronises. The popular idea is that there is no earth return from the MV to the HV and hence, no fault current, no step and touch potential issues, and little man...
  6. Rodmcm

    MTBF of PLC Systems

    Using supplier published MTBF and the e^(-lambda*T) methods for a PLC rack with CPU/Backplane and I/O the unavailability comes to a staggering 1900 hours a year.. Has someone got any sensible fault tree analysis information for PLCs
  7. Rodmcm

    MTBF of Protection Relays and other things

    Micom have a published paper that says that the MTBF of a P341 relay as 30 years. This gives a probability of unavailability of 287 hours/year (12 days) which seems ridiculous. Similarly a 16 module PLC rack, using the same idea of summated lambdas (1/MTBF) and probability of reliability as...
  8. Rodmcm

    Transformer Phase Capacitive Currents

    I am looking for some typical information on the phase capacitve currents of transformers. I have a specific need for the selection of a neutral earth NET/NER on a small generator. The specification requires the sizing to be the greater of 10A or 3 x Icap where Icap is calculated from the...
  9. Rodmcm

    Current Transformers and Burdens

    Hi I am going around in circles with CT burden calculations… Can someone assist Say we have the following Ip= 100A, Is=5A, Type=5P, ALF=10, VA=15 and say Rct=0.2 ohm, Rl=0.45 Ohm (50 metres of 4mm2) and Relay Resistance Rr= 0.004 ohm and the fault level is 900 A and the maximum running current...
  10. Rodmcm

    Diesel Generator Winding Pitch

    I understand generally the problems with not matching the winding pitch of generators synchronised together; this is the subject of several threads in this forum. What I do not understand is which pitch is better for an isonchronous load. I have a Cummins white paper dated 2013 that says...
  11. Rodmcm

    Reverse current into 20MVA power transformer

    An industrial site has a 14MVA 11kV load and 6MVA of embedded generation. The site is supplied from 2 x 20MVA transformers The 11kV breaker on each transformer is fitted with a 260A directional OC (back into transformer) which is graded with a 260A directional OC on the site incomer. Why would...
  12. Rodmcm

    Generator Transformer Vector and earthing options

    Hi We have an application for two 11kV generators to supply a local load and export to a 33kV system. The specification for supply says that the generators must operate in island mode so in this mode the 33kV will have to be earthed. We expect the 11kV should also be earthed for the local...
  13. Rodmcm

    Rim Generators 100 to 500KW

    Would anyone have any technical info or know manufacturers of Rim Generators of this size for tidal/hydro use?
  14. Rodmcm

    Harmonic Mitigation in Large Industrial Plants

    I have a client that has large block loads on an industrial plant that each have high VFD driven harmonics. He has implemtented mitigation ( active harmonic units) for one block and now is thinking about the second block to be commissioned next year. Using phase shifting power transformers...
  15. Rodmcm

    Synchcheck/synchroscopes and phase rotation

    I was amazed to learn that your average synchcheck relay will not detect the wrong phase rotation on one side (say a generator). Even the phase to phase ones! Also as I understand it the SEL300G does not detect this. How can this be! Surely, at commissioning the wrong rotation is a very real...
  16. Rodmcm

    Overexcitation on Synchronising with Decs300

    We are recommissioning a genset in a different location. It has a Basler DECs300 on it. Excites fine, good voltage control off line. As soon as we sychronise we go out on OEL Altered the hi set time but same effect. Can anyone shed light on possible causes? Other than trying to adjust the Hi...
  17. Rodmcm

    Shore to Ship Cables - 450V 60HZ

    Can anyone point me to a good supplier. These cables are marine grade flexibles. The sizes will be single core 300mm2 Cu
  18. Rodmcm

    Island Mode Generators - Load Acceptance

    A facililty has several old gensets plus a couple of new ones. They run them in an 'n-1' config for load.They have had several instances where if a genset trips then the others do not easily pick up the load. The fairly long delayed automatic load shedding comes into play and they loose big...
  19. Rodmcm

    Generator Quad Axis Subtransient Time Constants

    Gentlemen. I am between a supplier and a regulatory authority. The Supplier has provided a formula for the above as Tq" = Tqo" x (Xq"/Xq) using a Japanese Society formula. He says the derivation of Tq" is not mentioned in ANSI or IEEE for cylindrical rotor synch generator (air cooled 45MW) The...
  20. Rodmcm

    Connection of Dy generator unit transformer

    A client has a 6600kV generator and an 11kV/6600kV Dyn step up transformer. The generator has 3 neutral CTs and neutral is hard connected to earth. The 11kV synch breaker has the other set of differential CTs. Should the star point of the LV of the transformer be connected to anything, or left...

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