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  1. BK32

    Replacing a reverse acting AVR with forward acting AVR

    Thanks waross, Is there any benefit in connecting the AVR to the series winding over connecting it to the shunt (compound) winding? Will the response of the excitation system benefit in any way? I imagine that connecting the AVR up to the shunt winding as the series boost will require the AVR...
  2. BK32

    Replacing a reverse acting AVR with forward acting AVR

    Hi all, We currently have a requirement to investigate replacing our existing Jeumont Schneider reverse acting AVRs. The existing alternator is an indirectly self excited machine. The stator part of the generator excitation system comprises a differential compound winding arrangement (a shunt...
  3. BK32

    Unexplained tripping of circuit breaker

    Hi all, thanks for all your help. We ended up changing out the breaker with a spare and the new breaker was fine, no nuisance tripping. We are getting the suspect breaker inspected and tested again in the workshop. We did test for phase to earth faults as each piece of equipment came online...
  4. BK32

    Unexplained tripping of circuit breaker

    Hi All, Unfortunately, I have not been able to do much yet, as there are a number of other works being conducted within the space. I have conducted a phase-earth megger check with the Chiller Switchboard isolated at the incomer (i.e. just the suspect breaker at the main switchboard and feeder...
  5. BK32

    Unexplained tripping of circuit breaker

    Waross, I will have a look at both options upstream and downstream. I guess the assumption is that I am expecting that all other connections on all three phases are good (e.g assuming that there are no loose connections on the lightly loaded breaker. Also, generally speaking, if I use a 4...
  6. BK32

    Unexplained tripping of circuit breaker

    Again thanks for all your response. I believe that all the motor driven pumps start up without tripping off the short circuit release. Initially it appeared to be tripping off via thermal release protection. Measuring the Millville drop across the breaker poles will be a challenge as they...
  7. BK32

    Unexplained tripping of circuit breaker

    Thanks for all the helpful replies. I will check the tightness of connections at the breaker. Also, should the imbalance be traced through to a three phase induction motor feeder, noting an imbalance of approx 30% any advice on what may be a typical cause? Could it be improper alignment...
  8. BK32

    Unexplained tripping of circuit breaker

    Hi All, I need some help in troubleshooting an unexplained tripping of an MCCB. This breaker is installed in the main distribution board on an 440V, 60Hz, 3 ph, 3 wire system. The breaker is a cutler hammer (eaton) AQB-L250 type breaker with a 175A plug. The instantaneous trip setting is Lo...
  9. BK32

    Dahlander motor control

    Thanks parchie and jraef. Your responses were very helpful. I think I will need to do some reading on induction generators just to understand the principle in more detail
  10. BK32

    Dahlander motor control

    Just following my initial post, is there anyone that may be able to pass on any advice/info that may be applicable?
  11. BK32

    Dahlander motor control

    Hi all, I need some assistance with some investigation into a dahlander motor winding failure. The motor drives an axial fan via a direct coupling. Based on anecdotal reports the fault appears to be occurring in the following scenario: 1. The fan is operating in high speed; 2. The fan is then...
  12. BK32

    Current Injection testing for new MCC

    FreddyNurk, You mention that the only reason you would not conduct it post installation is if there was no access to the equipment in order to carry out the testing. These devices are largely installed in withdrawable units. They are all MCCBs with integral overcurrent protection and are not...
  13. BK32

    Current Injection testing for new MCC

    Thanks for your replies so far. Has anyone ever received advice from the circuit breaker manufacturer that the performance of current injection testing post installation would void the warranty? I have been told by some colleagues of mine that this has been the case in the past.
  14. BK32

    Current Injection testing for new MCC

    Hi All, I am currently involved in a new switchboard build project. We are currently having a new MCC manufactured for installation on a ship. The switchboard is to be integrated into a 440V system. The new switchboard is to be fitted with MCCBs fitted within integral overcurrent protection...
  15. BK32

    type 1/type 2 coordination for softstarters by anaylsis

    I am currently reviewing a design of a new Motor Control Centre, fitted with a number of motor starters, of which a number are fitted with Siemens soft starters. In the original requirements specification there was a requirement that all motor starter assemblies were type 2 coordinated...
  16. BK32

    Underspeed vs under frequency protection for diesel driven alternator

    Thanks all for your responses to my initial query. Waross to answer your question, the machine was installed circa 1985. It is installed on a auxiliary oiler replenishment ship. The DA is a 2MW shaft driven alternator (i.e. it is driven by a diesel engine via a reduction gearbox that also...
  17. BK32

    Underspeed vs under frequency protection for diesel driven alternator

    Have recently come across a generator with both under frequency and Underspeed protection. Both the under frequency and underspeed protection relays were connected to the generator ACB trip circuit. However the Underspeed relay was also connected to the "de-excitation" circuit. Once the speed of...
  18. BK32

    Generator governor troubleshooting - AVR defects

    Hi waross, point taken regarding use of the "load" terminology. From the responses provided, if I have understood correctly, it appears as though defects in AVR circuits would not normally have an effect on the governor, wrt kW sharing, unless there is common hardware/software? crshears, in...
  19. BK32

    Generator governor troubleshooting - AVR defects

    Hi, I have been recently made aware of an issue regarding erratic operation of a diesel alternator governor (or so it was reported) on a shipborne diesel alternator, part of a plant of three (3) 480kW DAs. The defect notice indicated that one of the DAs was load sharing eratically, continuing...
  20. BK32

    Use of deep cycle lead acid battery for standby application

    I have a question regarding the suitability of deep cycle lead acid batteries for use in a standby power application. Recently, a contractor has replaced a NiCad (vented sintered plate construction) 80Ah, 24Vdc battery bank (made up of 20 cells) , with 2 off Supercharge 12V, 80Ah (Model No...

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