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Thread: Elevator not starting on building power

  1. #1
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    Elevator not starting on building power

    I'm working on a new building with an elevator. During elevator startup, the motor is not able to ramp up to full acceleration, it won't get past the starting inrush. It starts up fine using temporary generator power. 208V-3PH, 60HP traction, with soft start (300% FLA). Stated voltage drop limitations from the elevator manufacturer are 5% running, 10% starting. Calculated drop is less than 2% running, 6% starting. Actual recorded drop during starting inrush is within the 10% limit. The upstream overcurrent device (400A breaker) isn't tripping. Any ideas?

  2. #2
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    May 2007
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    Westminster, MD
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    bizarre

    Hey Matt! The only reason I'm responding to this is that I see it's you. I don't have an answer.
    It appears that the generator is a more stiff source than the Utility.
    What size is the gen?
    I assume "won't start" means that the soft-start trips out? What trip indications do you get? Is the soft-start adjustable?
    Have you considered across-the-line? or is the soft-start part of the elevator offering?
    John

  3. #3
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    Thanks John!! I had the same thought about the stiffness of the source. I don't know what is actually happening when they try to start (posting this for a colleague who is the EE on the project). They brought in a 150kW generator to start it up. I asked about the adjustability of the soft start, waiting for a response. Utility source is a 4000A swbd, fed from a utility transformer.

  4. #4
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    A 4000 A service (>1 mva) won't start it but 200 kva will?
    how long and what size is the run to the elev controller?
    where do you hook the genset in to test? Does this shorten the run?
    when run off the service is there other bldg load?
    when run off the genset is it the only load?

    need the error/fault codes from the drive

    we just had a similar issue, we increased the allowable ol time on the controller



  5. #5
    Join Date
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    Most likely one of two things:

    1. You have a bad connection somewhere when connected to the utility power and it only rears its head when you are starting, meaning you have a severe voltage drop on only one phase and you are not measuring that phase so you don't see it.
    2. Your soft starter is too small for the load and the starting current never drops to a low enough level because the starter is current limiting all the time. But on the generator, the load causes the generator to slow down, dropping the frequency and allowing the limited current to create more torque (like what a VFD does) so it can accelerate.
    __________________________________________________ ____________________________
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  6. #6
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    Soft start settings

    There are usually a bunch of SS settings that are available. GUESSING here cause you do not say TRIPPING, If it is coming out of the electronics and is failing at the transition/run. The following should be looked at

    Ramp up time, usually given by the mfg of the equipment not of the starter Might want to extend this a bit, 1-2 seconds
    Torque boost, % and time extend the time 1 sec and boost 5%

    Then there is the dumb stuff that you have already done. Checked connections, meggered cables, verified settings are correct for your load.


    I will look about to see if I can find my old CH-Eaton soft start Excel spread sheet. You can put settings in and see the curve.
    If I can find it I will post it.

    D

  7. #7
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    Updating with some more information... The soft start is provided by the elevator manufacturer. It's not tripping, because they're not letting it run for more than a few seconds for fear of burning out the controller or motor (already replaced one motor). So I don't have any error codes to report.

    The elevator feeder has two splices in it. It starts as 2 sets of #3/0 Cu, transitions to 1 set of 750 Al for an underground run, then back to 2 sets #3/0 Cu. I suspected a bad splice, but they've been recording voltage drop on all three phases, and they're all within spec.

    EC wants to drop out the other building load and try to start it. On temp generator, there was no other load on the gen.

  8. #8
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    If supplied by the elevator mfr, there's a 90% chance it is a Siemens 72G Elevator Soft Starter, it's specially designed for that industry. It does not have most of the typical setting found in a lot of COTS soft starters.
    It's not tripping, because they're not letting it run for more than a few seconds for fear of burning out the controller or motor (already replaced one motor).
    Honestly, it's probably just needing longer to accelerate the motor than they are giving it... 2-3 seconds is probably too short of a time, it can take up to 30 seconds. The 72G soft starter has no "Ramp Time" settings, only Starting Current. The factory default is set for 425% of the UNIT rating (not the motor rating). It's the job of the elevator technician to make sure this setting is adequate to start the motor before it trips on OL. So if they set it to 300% of the motor FLA, it might take 10-20 seconds to start, but there is absolutely nothing wrong with that.

    If they burned up another motor in the past, it likely had nothing to do with it being soft started. Either that, or they did not properly set the OL trip current in the soft starter. A LOT of people do this totally wrong. They read article 430 and see that you are "allowed" to have the OL trip at 125% of the motor FLA, so that's how they set a programmable setting. But what they are doing wrong is that in the soft starter electronics, the 125% is ALREADY accounted for in the way the OL circuit works. So when the manual says "set it to motor FLA", that's exactly what you must do. If you set it to 125% of motor FLA, you are in effect setting it to 125% of 125% (156%), so the motor burns up if overloaded.
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  9. #9
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    I assume a traction with gear type counterweighted machine
    what is rated capacity? Rated speed?
    are the brakes releasing properly? I assume so since it picks with the genset

    will it run unloaded?
    is it stalling with rated load in it?
    I would start unloaded and add weight until it won't

    2-3 sec is not enough
    most can run at 300% for 20 sec or so
    60 sec at 150%
    the drive mfg/pn would help



  10. #10
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    Manual for drive mentioned above
    http://www.aesupply.com/pdf/Class72G...21_20053-3.pdf

    looks like it can be used on an electric or hydraulic machine?

    has ph rotation been checked?
    perhaps elev and genset are opposite?
    Last edited by Ingenieur; 09-05-17 at 04:56 PM.



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