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  1. dogzzz

    Help for generator

    Hi I am guessing your query and replying So what I understood there are two existing generators i.e G4 and G5. If any amongst G4 or G5 goes out G6 will come on board . Yes this can be achieved by designing an automatic transfer circuit , starting , synching and bringing G6 on line . This...
  2. dogzzz

    Input torque and speed for 1 KW generator.

    Yeah Bill you seems to be correct....I always dealt with megawatts....but wondering this 1 KW generator may spoil the equipments it is feeding to in case no frequency protection.
  3. dogzzz

    Water mist system for fire protection of electrical power generators

    Hello PRC Yes it will be effetive ,much better then gaseous suppression system. For a transformer ranging 50 to 60 MVA , roughly weighing 500 to 600 tonns , if undergoes a fault like short circuit , will result in core tempreatures rising upto 500 to 600 degree cecius. At these tempreatures the...
  4. dogzzz

    Water mist system for fire protection of electrical power generators

    We are going to install water mist type fire protection system for the Gas Turbine Generator (GTG) enclosure. One system for the Gas Turbine enclosure and the other one is for the Power Generator Enclosure. This is an upgrade project where the existing inergen system will be replaced with...
  5. dogzzz

    Input torque and speed for 1 KW generator.

    I guess you deal with 50 HZ . So ,4 pole , 1500 RPM motor , 1250 KW motor shall generate a torque of 6631 N-m torque and will be suited for generating a 1000 eKW. +/- 300 RPM shall mean that the generator frequency shall be 40HZ @ 1200 RPM (-300 RPM)( thus your generator breaker may trip due to...
  6. dogzzz

    Calculating Resistance and Reactance from positive sequence fault current

    Hi !! I will explain in a reverse way , by taking an example . Just ignore the material which is not relevant to you . Suppose you have to calculate the 3 phase short circuit at point A as shown below . As shown in blue is how we calculated the short circuit current , but in your case you...
  7. dogzzz

    Keeping the medium voltage motor warm by applying 400V to the winding

    A little different experience . Keeping motor warm : Normally we have 1 year gap between design stage and commissioning stage for offshore vessels , thus before commissioning the motors and generators are being dried out . -A low voltage 3 phase AC is applied , low enough so that the shaft...
  8. dogzzz

    Variable frequency drive

    My questions are: 1)) Is there any issue with using a 4-5 hP motor with a VFD even though the calculated Auger power is much lower There will no issues . I hope the VFD is rated for 5HP or 3.67 Kw. 2) My calculated Auger speed is 5 rpm; can I turn down the motor to 5 rpm using the VFD...
  9. dogzzz

    Measuring effective voltage and current across brushless DC motor

    Motor has permanent magnet rotor , thus will always perform synchronous operation , until somebody adjusts frequency at PWM .
  10. dogzzz

    VFD Minimum Output Frequency

    I agree with Skogsgurra , I have same experience , 0 HZ (6 motors , each 1500KW motor) just holding the load( holding the drill string from sea bed,standstill zero speed) , VFD worked fine no issues. Thanks
  11. dogzzz

    Measuring effective voltage and current across brushless DC motor

    Hi !! In your motor I can imagine that , the DC supply is feed to an inverter out of which 3 phases will come out , thus a resistor (voltage divider ckt) can be placed as shown in the photo calculate the voltage , and can ammeter be placed in series and thus V* I shall give you power consumed ...
  12. dogzzz

    LV Motor insulation resistance

    Thanks good info . Better to follow IEEE 43-2000 then Thanks
  13. dogzzz

    LV Motor insulation resistance

    Motor Insulation resistance yes in general when measured comes in the order of hundreds of meg-ohms. But there can be a condition that due to mositure or motor not being in use for few days the insulation resistance goes down. As per IEC 60364-6 for low voltage motors , @ 500/1000 V if the...
  14. dogzzz

    VFD in Class II Div 1 Area

    Applogies from my side too...if something offended you from my side.
  15. dogzzz

    VFD in Class II Div 1 Area

    whatever .......all I can say if anybody dont like anybodys post or replies or comments then simply ignore or make it correct . There is no need to play each others advocate.
  16. dogzzz

    Fault Current on Generators

    I see you point , thanks and lets close this !!
  17. dogzzz

    VFD in Class II Div 1 Area

    Did I asked you for your advice ?
  18. dogzzz

    Fault Current on Generators

    What you have told may be true for LV system (480 V) , but certainly not the case with MV . Who trips the breaker in first half cycle (10 milli seconds) , or in one cycle 20ms (50 Hz). Also it is mechcanically not possible because the breaker takes about 50 to 60ms to open. Thus a breaker with...
  19. dogzzz

    Fault Current on Generators

    Hello Scotty thanks for the wonderful book , I am planning to read it over the weekend and then may contact you . Hello Bill ...please see my replies in RED .... Let me try to walk through your comments and questions. The actual impedance is a machine characteristic and does not change...
  20. dogzzz

    Fault Current on Generators

    Hello All , My idea is not to let anybody down , but just want to learn from you guys . So , if you think I am wrong then please correct me , but please dont make fun , because like generator I also have my " DAMAGE CURVE ". Please find my views in red and there are some questions asked , if...

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