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Recent content by DmanD

  1. DmanD

    Low Volatge Drive Selection Guidance

    Hi Engineers, I am looking for guidance on selection of Low Voltage Drives on the basis of: 1.Dimensioning- torque,overloadability 2.Performance- V/f control, sensorless vector control,closed loopp vector control,static & dynamic accuracy of speed & torque, respose time Searching threads...
  2. DmanD

    Motor size classification

    Motor size classification is getting confusing. Some vendors are following Size classification other than the NEMA standard. Could you please help me with any information regarding correlation beetween the different size classifications?
  3. DmanD

    kVA rating discripancy

    Hi, I got a smoother waveform with notches of shorter time period which is considered within the 25%percent overload capacity of the rectifier. I guess the answer to my question belongs to some other aspect of the crane design - its gross nature!
  4. DmanD

    kVA rating discripancy

    Hi, [tab]Your conclusions are absolutely correct Gunnar Englund. The waveforms that I got were similar in four of my cranes having rectifier drives. Special Thanks Gunnar But does it hold true for the rectifiers which supply dc to the dc bus common to three drives? Because in this case the...
  5. DmanD

    kVA rating discripancy

    Hi All, [tab]It has become a great topic due to your super contribution. Kudos to you all. There is a flaw in my explanation that has caused you some confusion. EXTREMELY SORRY skogsgurra, scottyuk and sed2developer [tab]The rectifier gets 3-Phase AC supply from the alternator(DGset). The...
  6. DmanD

    kVA rating discripancy

    I have MX321 AVR in my genset and it is the best I believe. Does the controlled rectifier have very high harmonics? Still that would be included in its overload capacity of 125% isn't it? Still pondering D'man
  7. DmanD

    kVA rating discripancy

    PLease explain DAvid, the power going to motors through drives. The max power delivered to drive is through rectifier only. So the max power calculated from max rectifier should take care of it. Why does it need to be double?
  8. DmanD

    kVA rating discripancy

    Hi, This question is baffling me ever since I am working in this crane. This crane lifts containers of max. load 40T. It uses rectifier-drive for control of all motors. The kVA rating of the diesel generator set is 670kVA. CAlculating the max kVA load including all auxillary drives, it comes to...
  9. DmanD

    DC injection heating

    Edison 123, You are absolutely perfect in this topic. It has worked nicely on one 670 kVA alternator. It took me 11 hrs to get the IR to 4M? from 0.5M? with meggering being done every hour after first 3hrs. This is a first in this company. Accolades for you Thanks from the depth my heart D'man
  10. DmanD

    DC injection heating

    Two types of alternators are available with us here - 670kVA and 551kVA. The exciter ratings are very close 43V,2.5A and 45V,2.5A. respectively. Further two new ones have arrived with rated output of 505kVA. All the ratings are alike varying 1 or 2 units max. If you require Edison I will...
  11. DmanD

    DC injection heating

    Dear Edison123, You have explained the process in a very clear way. ACCOLADES for you. One small doubt is that we have got a single phase supply near the place. What are the disadvantages of using that? We have two newer alternators of 505kVA rating but the exciter is shaft mounted with...
  12. DmanD

    DC injection heating

    Hi, It was a hectic week for me. I have gathered details of the alternator in question. Make: Stamford HCI 1500rpm 670kVA 400/231V 732A 50Hz Exciter Voltage=43V Exciter Current=2.5A It has a DC exciter. The alternator is coupled with a Cummins engine. Thanks D'man
  13. DmanD

    DC injection heating

    Thats nice Edison, do you run the alternator at full speed or less than that. What method are you using to control the exciter current? The time period given by you is exactly what we desire. D'man
  14. DmanD

    DC injection heating

    Hi thanks for the input. I had the idea that there must be some rules like the ones followed for transformer heating. OK, I will go by the rule of 10% rated wattage. What to do with the connections of shaft mounted diode rectifier? They have to be isolated isn't it? The IR should actually go...
  15. DmanD

    DC injection heating

    Hi, With 2 of our alternators down with IR value of 1M? it is a precarious condition for us. Any one of the working alternators gets broken down then it would be disastor. The heating with sodium vapour lamps and heat radiators is proving to be very slow. I need your help with the...
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