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  1. Guardiano

    Aternator current

    All the cables enter through a steel gland plate. We checked for loose connections but could not find one. Could Eddy current be the cause of the current unbalance? The steel gland plate is quite hot. Guardiano
  2. Guardiano

    Aternator current

    Thanks Cranky108. The current reading is OK as the cable drawing the higher current is hotter.
  3. Guardiano

    Aternator current

    Hi, We are commissioning a 2000 k VA generator and the current on each phase is balanced. There are four single cores cables per phase but the current on each core is not balanced at all. The cables are run in trefoil. What could be the cause? Thanks Guardiano
  4. Guardiano

    Zonal Protection

    Hi forum members, I understand that class X CT is always used for differential protection because you don't want the protection to work for external fault. I have seen some applications where 5P20 CT is used for differential protection. Does this compromise the installation? Any comment is...
  5. Guardiano

    Motors in tandem

    Thanks Edison. See picture.
  6. Guardiano

    Motors in tandem

    Hi, We have two 5 MW 6.6 k V wound motors driving a crusher in tandem. We have always been running the crusher with the two motors powered. Now because of load reduction, only one motor is powered and the powered electric motor drives both the load and the second motor. We noticed a very strange...
  7. Guardiano

    Fixed MV Circuit Breaker

    What about SF6?
  8. Guardiano

    Fixed MV Circuit Breaker

    Dear Forum Members, I understand that the only means to safely isolate a medium voltage circuit breaker is to take it out and padlocked it in the test position. What about fixed circuit breakers? Could the spring charged mechanism be used to safely isolate a fixed circuit breaker? A circuit...
  9. Guardiano

    Torque to be applied

    Hi All, Some feedback. We took our time(10 days) and tightened the bolts incrementally. At 3420 Nm, there is now a 3 mm gap between the inner and outer rings and no more tightening is possible at this torque. The original shaft tolerances were (730-0.024)mm and (730 -0.072)mm. The new shaft was...
  10. Guardiano

    Torque to be applied

    Hi All, We finally found the manual and the recommended torque is 3400 Nm. We already torqued to 3600 Nm but the outer and inner rings are still not aligned, see the picture in my initial post. There is a gap of about 30 mm between the outer and inner rings. The gearbox was removed because the...
  11. Guardiano

    Torque to be applied

    Thanks All for the great posts. Dear Desertfox, I quote what you wrote. "Firstly I would check any maintenance manuals for the gearbox and see if that gives any torque figures and whether or not the bolts are lubricated prior to tightening, lubricating bolts will have a dramatic affect on the...
  12. Guardiano

    Torque to be applied

    Dear Forum Members, I don't know if this is the right forum but I'm sure the gurus present would shed some light. We have a gearbox arrangement and the motor/gearbox assembly drives a shaft which itself drives a conveyor. The gearbox was removed for maintenance and now it has just been put into...
  13. Guardiano

    Hi Forum members, We experienced a

    Hi Forum members, We experienced a stainless steel basket failure on one of our sugar centrifugal machine. The basket spins at a maximum speed of 1100 RPM. I am attaching a picture of the tear. Any reason for the root cause ? Thank you...
  14. Guardiano

    Switching

    Dear Forum members, We noticed a strange phenomenon when we switched on a 5000 k VA 11 k V/ 690 V transformer on the grid. The grid was lightly loaded before switching and around 800 k W was imported.The grid metering showed export of some VA for a few seconds. Any explanation ? Thanks Guardiano
  15. Guardiano

    Dual driven generator

    Dear Forum members, We are working on a preliminary phase of a project which will include a 10 MW alternator driven by a steam turbine. The turbine will operate only for six months of the year and power will be supplied through a diesel driven generator for the remaining six months of the year...
  16. Guardiano

    Starting

    Hi everyone, I have a 250 kW compressor on site and due to lack of load, the compressor is recycling every 50 mins. The compressor is driving a compression chiller and is star/delta started. I understand that one restart every 45 minutes should not be a major problem but I presume that the...
  17. Guardiano

    VSD

    Dear Waross and Jraef, I'm measuring the potential to ground on the incoming supply to the pump. We did also measure on the LV side of the transformer too. Both sides showed a rise in the potential to ground voltage. I'm using an industrial true RMS meter, Fulke 87, for this purpose. Thanks...
  18. Guardiano

    VSD

    Dear forum members, I am having an issue with a 400 k W pump. The pump is driven by a variable speed drive.When the pump is started, it ramps well to rated speed and the current on the three phases are very well balanced at nominal speed. The pump pumps well and there is no issue with the pump...
  19. Guardiano

    Design

    Dear Forum memebers, I am having a discussion with a design engineer regarding the installation of two 3.0 MVA 400 V diesel sets. The sets will be used to feed the grid at 33 k V. The consultant is proposing fuses on the HV side of each 400 V/33 k V generator/transformer and a common 33 kV...
  20. Guardiano

    Motor Starting

    OK LionelHutz, I did not give enough informations. This 5 MW motor forms part of a plant and was only to be started after completion of a power plant project. Now, there is a need to test this motor and the utility transformer is too weak to get it started, only 2 MVA. A basic calculation gives...

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