Failure Analysis Burning : LUSENET : Elevator Problem Discussion : One Thread

Hi all,

If anyone out there knows, please inform of the issues involved in the following case: What can we learn of hydraulic elevator system problems by viewing the burned contacts of a wye-delta starting unit. A system I am dealing with requires that we change the contacts EVERY 3 MONTHS. Also there seems to be more pitting and burning on one set of the contacts. All I have is the contacts but I dont know which set is the wye side or the delta side, but I think it is the delta run side with worse degradation

Any response would be great!

-- Noel (, November 11, 2004


sounds like your initial start up is way to much amps, I assume you have a seperate star contactor as well,possibly worth checking fuses in main board, as I have heard of underated fuses put in and things blowing in panel, hope this helps.

-- kvs (, November 11, 2004.

this normal for a hydraulic elevator, because of KW involved of the submersible motor in comparison with a normal traction machine. check the rating of the contactors and compare it to the Motor Amps. you can have what so called soft starter installed which will bring down the burning. this is caused by the change over and normally to the Start Y contactor. you must have a safety on line contactor, contacts of it are in series with the delta contacts once you have burning too much in order to ulluminate a stuck in contacts situations. also put in a bigger contactor.

-- (, November 11, 2004.

If you have recenly taken this on, you may need to check the history with the builing custodian. Has it had a motor rewind/replacement before you took over? If so is it oversized(amps-wise)? If not, have you checked it's starting current ,runing current on both star and delta? and compared them with the contactor rating? The burning on these systems is normally the Delta contactor as it is the one that absorbs the discharge when stopping. Which leads to the question of is it dropping quick enough? Does it have a small half wave or Zenner diode across it to make sure its magentic field collapses quickly ensuring instantanious "off"? Is the air gap big enough in the contactors? After all you may be replacing "like for like" with what is not original equipment to start with. Sorry to sound like I am teaching Granny to suck eggs but it sounds like it may be a case of back to basics.The option of fitting a small soft start in line with the star contactor may be worth persuing, but it will have a short "wind up" time as it may interfere with other electronic feedback curcuits on the controller,such as a timer monitoring how long star is energised for. good luck

-- geoff judge (, November 12, 2004.

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