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Thread: Elevator not starting on building power

  1. #11
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    Quote Originally Posted by Ingenieur View Post
    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?
    Ooooh... EXCELLENT point! The Soft Starter will accept either, but only one at a time. So if the two sources are different, it may help to explain why it works when on the generator!
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  2. #12
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    Quote Originally Posted by Jraef View Post
    Ooooh... EXCELLENT point! The Soft Starter will accept either, but only one at a time. So if the two sources are different, it may help to explain why it works when on the generator!
    something doesn't add up
    it can pick with the genset which has a starting kva of 450 or so with 35% v drop
    the motor needs 300% or ~ 165 kva, so drop should be very small
    genset 150 kw / 185 kva

    but it can't start with 1 mva xfmr ? Which if even 50% load can provide as much or more?
    plus he measured drop and it is within limits
    be nice to know the actual drive model
    this one is rated at 200 vac so a 4% drop from 208 would be moot
    operating spec: -15%/+10% 200-460 VAC
    imo v drop is not the issue

    where was the genset connected to the ckt?
    Last edited by Ingenieur; 09-05-17 at 06:20 PM.



  3. #13
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    I've seen it happen. When on the genset, the load burdens then slows the generator, which lowers the frequency as the voltage drops. So that actually is what a VFD does too, meaning you will actually get MORE torque per unit of current than if the frequency was correct. Then the generator brings the motor up to speed with it as it recovers from the step change in load. The first time I had this happen was at the Ford Island Bridge in Pearl Harbor, the drawbridge you go on to get to the USS Arizona memorial. When running on the backup generator, the starters worked to power up the hydraulic power units but when connected to the utility power, they tripped on OL before they could accelerate the motors. I got a free trip to Hawaii on that one. I tweaked the settings on the Soft Starters in about 10 minutes, but didn't tell anyone for 3 days...

    The tricky part is that the Soft Starter must be tolerant of the frequency drop and continue functioning. Some are, most are not. So MOST of the time, the soft starter will trip on Under Frequency and nobody knows that it MIGHT have worked if it had not tripped first. But Nordic Soft Starters (and A-B and Motortronics who I worked for) use a somewhat unique firing circuit, so they are (were) insensitive to frequency drift. Nordic was part of Furnas who was bought by Siemens and is now gone, the only remaining product that Siemens sells that is made from that older technology is the 72G, because getting approvals on elevator controls is a logistical nightmare and incredibly expensive. So Siemens wisely left that product alone, selling it exclusively to elevator OEMs.
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  4. #14
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    May be the remote possibility that utility has a much higher harmonic distortion than that of generator so that actual power input to the motor through soft starter during starting is lower on utility supply than on generator supply and hence longer time to ramp up. A comparison of harmonic distortion of utility and generator supply may reveal it.

  5. #15
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    Does the direction of travel affect the behavior? Cable elevators are counter-balanced. I believe at half the rated lb rating.

    It's usually not doing real work when its just one or two people going up but it is working at full load going down to hoist up the couterweights.

  6. #16
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    elevator motor wont go

    jraef,

    Looks like everyone is headed in the same direction, I thought your answer was written exceptionally well. I do a ton of elevator motors, dc, mostly, but I remember winding old OTIS AC two speeds. What I don't get around [ yet ] is the new AC traction motors. I get the freq lowering the strain and it all makes sense but 20-30 seconds seems forever, in the 30 seconds is it accelerating?

    I can see the lower current via lower freq and you know that controller, but it just seems forever to eat 30 seconds, hell I see these elevator guys get beat up if someone has to wait 30 seconds, for the only car that goes to the 40th floor, very interesting, and again very well written

  7. #17
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    Is the soft start used when on the utility supply? The original post seemed to suggest otherwise.
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  8. #18
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    Quote Originally Posted by Electric-Light View Post
    Does the direction of travel affect the behavior? Cable elevators are counter-balanced. I believe at half the rated lb rating.

    It's usually not doing real work when its just one or two people going up but it is working at full load going down to hoist up the couterweights.
    counter weight = car wt + over wt
    over wt is typically 40-50% of rated capacity



  9. #19
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    Quote Originally Posted by Ingenieur View Post
    counter weight = car wt + over wt
    over wt is typically 40-50% of rated capacity
    Yeah. Meaning that the horsepower draw is at the lowest when cab loading is at about 50% of rated load. So, this means the full hoisting effort is roughly half the rated poundage. Therefore, the maximum power draw is raising the cab at full load, or lowering the cab empty. Why is this important? If it comes down fine empty, then it shouldn't have problem stating up fully loaded.

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