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  • Users: Ryc92
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  1. Ryc92

    Induction motor vector control

    Hi, Maths question here: Induction machine rotating frame voltage equations: Vqs = RsIqs + d(flux linkage qs)/dt + (omega x flux linkage ds) Vds = RsIds + d(flux linkage ds)/dt - (omega x flux linkage qs) Sorry I couldn't do the symbol for flux linkage, omega or the differential operator...
  2. Ryc92

    DC essential service system earth fault

    Hi, Many thanks for the replies. We have just turned the protection down to 5Kohm and the fault hasn't dissapeared on the charger it was on (surely indicating that the IR of the earth path is less than 5Kohm?). Interestingly however, whereas before the charger for the other string of batteries...
  3. Ryc92

    DC essential service system earth fault

    Hi there, We have a 250V DC UPS system here (CCGT power station), fed by two strings of batteries (125V DC string, 250V across both) and three battery chargers (two dedicated to each string, one with a changeover switch to charge either string). On the charger for one of the strings (and also...
  4. Ryc92

    Coordinate transform

    Hi, Many thanks for taking the time to reply. The mix up of symbols is purely accidental, but thanks for noticing. I believe the difference in transform depends on whether the Q axis leads or lags the Direct, and I am glad to hear it is purely convention lol. Sorry, I meant to write the next...
  5. Ryc92

    Coordinate transform

    I am currently studying the use of a coordinate transform for the analysis of polyphase electrical machinery. I am having trouble understanding the transformation angle used in such. For example, consider the transform of a three phase winding carrying current to any abitrary reference frame...
  6. Ryc92

    Synchronous generator

    Here's one for you... Consider a synchronous generator, rotating field, operating in stand-alone at a given load when a sudden increase in load on the armature occurs (say a large heater is turned on). Let's say the excitation voltage/current on the field winding is held constant and the prime...
  7. Ryc92

    electromagnetic torque

    Ahh okay, I believe you are saying it is a question of convention rather than actual relationship? I have attached a rudementary phasor diagram which explains what I mean, notice that the armature flux is pointing down towards the mutual flux, whereas the armature current which is producing the...
  8. Ryc92

    electromagnetic torque

    Thanks I'll have a think about it and see if I can make sense of it! Any ideas on my next problem?
  9. Ryc92

    electromagnetic torque

    Yeah having looked at your derivation I realise I am not quite ready for that! Thanks anyway, at my stage of learning I tend to accept more than I question. I can understand it in terms of the usual cross product torque relating to mechanical force in terms of the quadurature component times...
  10. Ryc92

    electromagnetic torque

    Hi, Can someone good at maths explain to me why electromagnetic torque in a machine is proportional to: MMFstator x MMFrotor x Sin delta I don't understand why it is the product of the field and stator mmf? I have looked around on-line but all I see is this equation stated but not derived...

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