Overhead Bridge Crane Motor

Discussion in 'General Electronics Chat' started by Travis1, Dec 16, 2014.

  1. Travis1

    Thread Starter New Member

    Feb 25, 2014
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    Good evening all,

    Had a quick question about an overhead crane I wired today. The crane is operated by hand held controller and moves right-left on a rail system.

    I installed it. Motor ran. Crane ran fine from left to right. However, crane is now stuck to the far left side of the rail. There's power to the hand held controller. When "left" and "right" buttons are pushed the contactors (or relays if you prefer) inside the control panel close, circuit is then closed, but no power to the motor. No tripped breakers at all. Crane stays put.

    Hard to tell without looking to be sure, but basically I'm wondering why a motor would not be receiving power even though contactor coils are closed.
     
  2. #12

    Expert

    Nov 30, 2010
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    2 options. Either you missed something installing it or something is broken. Contactor might be closed properly, but you missed a power connection on the contactor...or one direction of the motor won't start.
    That's about all we can say with the information provided.
     
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  3. Travis1

    Thread Starter New Member

    Feb 25, 2014
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    I hear you. I'm just wondering why it was able to go through the full range of operations for several minutes and then just stop entirely.

    Something that I noticed that was odd - I removed the plug-in controller from where is plugs into the motor/gearbox housing and the crane moved down the rail on its own 4 or 5 inches. Any reason a motor would move without any connection to the controller?
     
  4. #12

    Expert

    Nov 30, 2010
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    That would indicate that something broke. Maybe a connection wasn't exactly tight? Maybe an overheat sensor popped on one winding? Maybe the controller board smoked a transistor? Just guessing, of course.

    Crawl in there and double check for obvious flaws. After that, it's chasing the circuits down with a VOM.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Did you wire the crane or just connect it up? IOW are the contactor coils wired through over loads? It should be easy to trace the power from contactors through to the motor, generally fed through a festoon cable to the crane motor?
    Is the control panel carried by the crane or situated separately.
    Max.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
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    However, crane is now stuck to the far left side of the rail.

    Since you are at the end of travel, have you checked for a limit switch of some sort.
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Your name is travis, so I'll assume you aren't located in mumbai, and are subject to the laws of some U.S. state. FYI in most states, working on cranes, even shop gantry cranes like this, typically requires a license (example). Doing the work without the license opens you up for liability that you don't want any part of. Now that's out of the way and I'll assume you have the license.

    Is the crane powered by festoon cable or by bus bars with brushes? If bus bars, check to make sure the bus bars actually extend to the end; you won't be able to see from the ground, as they are covered by plastic guards. Could be it just ran off the end of the bus bars, or the brushes came unseated.

    You say "no tripped breakers at all" and then "hard to tell without looking to be sure." Can I assume that means you're standing on the ground pressing the button and hearing the contactor and making assumptions about the state of the "breakers"? The crane could have "starters" which are contactor+thermal overload in one package, or it could have separate contactor and overload; in either case there could be a scenario where the contactor could close but the 3phase power is still interrupted by the overload.

    Could be a jammed limit switch although not likely considering the contact closes; you would think a limit switch would interrupt the coil power.

    Are we talking about a Sew Eurodrive Movimot?
     
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  8. JWHassler

    Member

    Sep 25, 2013
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    Have you manually operated the contactor? You might have to move crane off the limit-switch.
     
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Also could be a brake failing to release
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I'm impressed with all the good thoughts immediately stumped up by others with better first hand knowledge than myself here.

    I did wonder if there was something about the 'end of travel' or even overrun that disconnected the crane and I see there are several possibilities to check.

    So use the MK 1 eyball. (edit oops the MK1 is the one without the e)

    However two comments by yourself also struck me.

    Firstly you say it ran all right to the left hand end and stuck there, but did not actually say that it ever ran correctly in the other direction.
    Later you say it was able to go through the full range of operations.

    Please confirm this as it is unclear if it ever went to the right or if the handheld controller button is at fault.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Also i would like to know whether the statement of 'wired the crane' means connected the power to a pre-engineered crane or wired the control for it?
    Is it a known make such as Demag?
    Max.
     
  12. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Normally those cranes are hardwired with heavy duty limit switches at the end of each side (in some cases even TWO limit switches per side). If you wired the whole thing yourself, then it is possible that you miswired those switches in such way that when one of them is actuated it will not only stop motion in that direction but in ALL directions...
     
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