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How can I optimise, with or without braking resistor, braked stopping of the ATV312, ATV61 and ATV71 variable speed drives?

Braking

When there is high inertia in the load to be decelerated and the deceleration ramp imposed by the drive is too short, energy is restored from the load to the drive.
This involves this generated energy being stored on to the drive DC bus capacitors.
This storage then generates a voltage rise on this bus which must not exceed a critical threshold otherwise the drive will be damaged.
 

As long as the DC bus voltage is below the permitted voltage threshold, the drive follows the deceleration ramp by charging the capacitors with the excess energy, which allows the load to be braked.

But as soon as the maximum voltage threshold is reached, to be able to keep control of the drive and not stop in freewheel mode following an OBF fault, the operator will have to choose between two solutions:

  • Braked stop by ramp adaptation
  • Braked stop by braking resistor

Braked stop by ramp adaptation

The drive no longer continuously brakes the load, it switches to "freewheel" mode, this means there is no more excess energy to be absorbed by the drive, the capacitors are no longer charged.  On the contrary, they discharge and the DC bus voltage decreases until it reaches a minimum threshold below which braked stopping on ramp is re-enabled.  The load is stopped by a succession of braked stops and freewheel stops, and braking is optimised but has a variable duration if the inertia of the load is constantly changing.  This is to avoid the drive tripping on OCF.
 
Settings

ATV312 (or ATV31)

FUN menu => StC => Stt = rMP
FUN menu => rPC- => BrA = yes
 

ATV61 and ATV71

Menu 1.7 Application funct. => STOP CONFIGURATION = Ramp stop
Menu 1.7 Application funct. => RAMPS -> Dec ramp adapt. = yes
 

Braked stop by braking resistor

The extra energy is transmitted to the braking resistor and is dissipated by the Joule effect.
If the braking resistor is the correct size, the load is stopped for the period configured by the deceleration ramp parameter, irrespective of the load.

Settings

ATV312 (or ATV31)

Connect the resistor between PA and PB
FUN menu => StC => Stt = rMP
FUN menu => rPC- => BrA = No
 

ATV61 and ATV71

Connect the resistor between PA and PB
Menu 1.7 Application funct. => STOP CONFIGURATION = Ramp stop
Menu 1.7 Application funct. => Ramps -> Dec ramp adapt. = No 

Faults

OCF and SOF
OCF (Overcurrent) and SOF (Overspeed) faults may be linked to a high-inertia driving load connected to a drive set to a ramp stop but without a braking resistor with the ramp stop adaptation parameter (BRA) set to No. 

To resolve the problem, there are two options:
 

  • Add a braking resistor and configure the drive as Braked stop by setting the BRA parameter to NO .

Or

  • Set the drive to a Braked stop by ramp adaptation.


The braking resistor does not heat up and the drive deceleration DEC ramp is not reached

  • Check that the braking resister is connected correctly to the drive
  • Change the settings to Braked stop by braking resistor  (BRA set to NO)
  • The power transistor which can release the excess energy into the resistor has failed
FA23699  |  07-Mar-2014  | Settings
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