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Discuss After installing Inverter Drive, two motors now running at different speeds? in the Commercial Electrical Talk area at ElectrciansForums.co.uk.

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  1. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    We've just put in a bread cooling conveyor system. It has two sections, 8ft, and 25ft. Each belt has its own motor, both being 3PH, 230v. Each motor draws approximately 2 Amps. We put in a 5 HP Lenze Inverter Drive to control both motors because, before installing the Drive, both belts were running at the same speed, and a bit too fast for us. Now, with the Drive, the 25ft belt is noticeably slower than the 8 footer. Help?
     
  2. snowhead
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    snowhead Trusted Advisor

    Location:
    Mildlands
    Are both the motors identical?
    Are both the pulley sets identical sizes?

    Are the speeds different with no load and full load on the belts?

    Given the vastly different lengths, the load on the motor with the longest belt is going to be higher.
     
  3. Andy-1960
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    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    Is the drive you have selected constant torque or variable torque, conveyors should have constant torque drives.
    It is also much better practice to drive motors from separate inverters in this type of application, (especially when the loads on each motor are different) and use feed back from one drive as a reference for the other.
     
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  4. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Snowhead, both motors identical, chain drive with same size sprockets, or gears. The belts moved at the same speed, loaded or not, before installing the Inverter Drive. Manufacturer says belt lengths in this case, not a factor.
     
  5. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Andy, the drive is constant torque. Mfr. says belt lengths not a problem.
     
  6. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Andy, the Mfr. says one Drive is OK for this application.
     
  7. Andy-1960
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    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    The drive manufacturer may say it is fine for this application (even though it obviously isn't !) I said it is better practice and in this case had you fitted two drives, you would not have a problem.

    As you have been talking to Lenze, what do they think the solution is.. have they made any suggestions?
     
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  8. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Andy, I too thought we'd be better off with two drives, but Lenze says not. They think it's a *slippage problem*. (One hell of a slippage problem, if you ask me, and obviously, I don't know a hell of a lot about this, and neither did two contractors we've had look at it. So far)
     
  9. Andy-1960
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    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    Have both the motors been fed by separate cables from the control panel?
    What is the length of cable from the panel to each motor?
    Do both motors have the same number of poles?
     
  10. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Both motors are fed by the same cable. The distance from the panel via a disconnect and the Lenze controller to the first motor, located on the 25ft section is around 60ft. The distance from this 1st motor to the 8ft section motor is about 25ft. The motors came from Turkey and are identical. I'm not at the bakery at the moment, so I don't know the Hz of the motors, 50Hz or 60Hz, which is used here in Canada. Thinking back to the Lenze conversation, they mentioned that a 50Hz motor would not be as fast as a 60Hz motor. Still, why did both belts run at the same speed, loaded or not, before the controller was put in? If we do go with a second controller, I realize that we'll have to run a second cable.
     
  11. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    This can often happen when existing motors have retro VFDs fitted and it probably is slip. How difficult is it to swap the motors over to see if the problem lies with the motor. No two motors are likely to be identical even if to all intense and purpose they are identical especially as they have both been in service and may have suffered different wear and tear.
     
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  12. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    westward10, good thought. The motors are brand new. Have only been run a few times.
     
  13. Marvo
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    Marvo GMES....You absolute beauty. YOU ROCK DUDE!!!! Staff Member

    Location:
    South Africa
    Slip = heat. If one of the motors has high slip it will be running hotter than the other if they're under the same load.
     
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  14. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Thanks, Marvo. The longer section is 3 times the length of the shorter piece, 25ft to 8ft. Will check for heat difference.
     
  15. bob unitt
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    bob unitt EF Member

    Location:
    Burlington, ON
    Andy, problem solved! One of the motors had been hooked up as 440v, when it should've been set to 230v, hence the much slower movement. What is happening here?
     
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