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  1. #1
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    ACH550 brake chopper activation

    Hi all,
    I am new to this forum and am looking for someone familiar with the electronics of the ABB ACH550-024A-2 product. I have purchased one of these units to run a table saw, specifically to convert single to three phase. I want to enable the internal brake chopper which is disabled on this model. The ACS550 has the chopper enabled. The ACH has the exact same part number power and logic boards as the ACS and I have physically confirmed that the hardware exists. I suspect that when one orders the logic board, it is either flashed for ASH or ASC. Since my application is so simple, all I really want is to activate the internal chopper. The control difference appears to be that the ACH has no access to the 2005 command whereas the ACS does access this command.

    My question:
    Is there hidden access to any, specifically, the 2005 command on the ACH550?
    Is it possible to reflash the logic board to an ACS model?
    Short of a SW solution, is there a HW mod one can make to enable the internal chopper?

    Thanks in advance for any assistance anyone can offer!!

  2. #2
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    Do you have a question about heating and cooling?
    AOP Rules: Rules For Equipment Owners.

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    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
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    Questions should end with a question mark "?" Statements end with a period "."

  3. #3
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    Sir, I think you may have the wrong forum...
    The TRUE highest cost system is the system not installed properly...

    Find a HVAC-Talk Contractor by clicking here

    Do you go to a boat repairman with a sinking boat, and tell him to put in a bigger motor when he tells you to fix the holes?

    I am yourmrfixit

  4. #4
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    Im pretty sure that the drive you have doesnt make a 3rd phase from a single phase source. You need a frequency converter to do that. A rotary converter or some VERY expensive transformers. It's simpler to buy the right motor for the saw.

    The hardware mod is to buy the correct drive.

  5. #5
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    Thread Starter
    Thanks everybody for your responses. Since th ACH550 is a HVAC VFD, I was hoping someone may have had the opportunity to need the braking function for some specialized task and potentially have encountered and solved this. For those interested, the ACH550 is a VFD so will convert single to three phase. It does this by first converting the incoming ac to a DC bus. Three switching converters then construct the three phases from this DC bus. You do need to derate the power as long as you stay within the current rating of the converter.

  6. #6
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    Moved to Electrical forum.
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    How many times must one fix something before it is fixed?

  7. #7
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    Thread Starter
    Quote Originally Posted by beenthere View Post
    Moved to Electrical forum.
    Thanks VSTECH!

  8. #8
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    Thread Starter
    Opps, thanks beenthere!!

  9. #9
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    Fairly sure the drive can do what you want and you can also run a three phase load from a single phase input but the drive has to be sized for it. You can't run a 460v motor from a 230v source as there isn't enough D.C. Bus voltage(not that that question was asked)

    I would talk to Abb tech support or the local rep office for help. I am certified in startup for Abb but that is advanced functions. Yaskawa calls it D.C. Injection breaking. Abb calls it trickle current. It's a voltage signal for when the drive has 0 reference. So basically at 0 reference the drive will output 3 to 5 volts to lockup the motor...

    I think that's what your describing.
    "If history repeats itself I am so getting a dinosaur"

  10. #10
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    Thread Starter
    I have an oversized (derated) 240V VFD version running a 240V motor and do have the VHD working well doing the 1-3 phase conversion. So all is well there. I CAN decelerate the blade as fast as ~5 seconds without triggering overvoltage. But any faster and the overvoltage controls kick in to limit the returning energy. I'd like to get that down to 1-2 seconds or less if possible. The type of braking I am looking to access uses an external braking resisistor and the internal chopper. As I understand it, both DC injection and Flux braking move some of the losses to the motor but still dump energy back to the converter, thus limiting how fast the motor can brake. Whereas using an external braking resistor dumps the energy to the resistor. That said, I will try DC injection and flux braking and see how fast I can get the blade to stop. Still believe though that fastest deceleration can be had usng a braking resistor (which may prove impossible with his unit!!).

  11. #11
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    Can you disconnect the motor from the VFD upon a Stop signal without it going into fault? If so, wire up your own braking resistors with external contactors that just disconnect from the drive and then short the motor to the resistors. I assume that the HVAC drive has the software stripped out of it, even if the hardware is there - it's how the manufacturers "add value" to the higher end products these days. I dunno what the firmware update procedure is, but maybe you can load the ACS firmware onto your ACH drive? Probably won't work though.

  12. Likes HPCBOB liked this post
  13. #12
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    Thread Starter
    That's an interesting suggestion! I may even be able to repurpose the contactor on the saw. Don't know if I could disconnect without faulting the VFD but don't see why not. Easy enough to check. Probably will need to add some sort of clamp to limit the voltage flyback but should be doable.
    It's not looking too promising for some back door command way to access the 2005 command....

  14. #13
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    Quote Originally Posted by HPCBOB View Post
    That's an interesting suggestion! I may even be able to repurpose the contactor on the saw. Don't know if I could disconnect without faulting the VFD but don't see why not. Easy enough to check. Probably will need to add some sort of clamp to limit the voltage flyback but should be doable.
    It's not looking too promising for some back door command way to access the 2005 command....
    If you wanted to use a single contactor, you would have to get one that has both NO and NC contacts. NC contacts connect to VFD, NO contacts connect to braking resistors, and both sets of contacts are tied together on the motor side. Otherwise, you would need two contactors with a mechanical/electrical interlock.

    Upon stop command, enable contactor until motor is stopped, or for a given time period, then release and hope that the voltage is low enough to not trip the drive. Maybe use some kind of voltage detector to determine when to release the contactor and reconnect the drive to the stopped motor.

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