58 Rockwell Automation Publication 750-QS100B-EN-P - August 2020
Appendix A Reference Information
To help prevent faults that are related to overload and overcurrent conditions, acceleration time must be set to the
capabilities of the drive based on the load and application requirements. The normal solution is to set parameter 10:1915
[VRef Accel Time 1] to a longer time period so that an overload or overcurrent condition of the drive does not occur.
To set parameter 10:1915 [VRef Accel Time 1], incrementally increase the acceleration time by a 30 second interval, and
after each increase, restart the drive. Repeat this process until the load is able to start without a fault condition. The
maximum acceleration time for most applications is up to 5 minutes, however high inertia loads could require higher
acceleration times. For example, 30 minutes may be common for a centrifuge. If faster acceleration time is required for
the load, contact your local distributor or Rockwell Automation® technical support for further application review or
potential drive sizing considerations.
Recommendation
If the load has a large inertia value, and acceleration time is not an application concern, set the current limit of the drive in
amps to the continuous current rating of the drive in amps. This current limit setting lets the drive apply its rated current
to the motor on a continuous basis until the application reaches full speed. The overload current setting is configured in
parameter 10:222 [Current Limit 1]. Default values for this parameter that are time limited equal 110% of the Normal
Duty (ND), or 150% of the Heavy Duty (HD) rating of the drive that may have induced a hardware overcurrent fault. To
obtain the continuous current rating of the drive, see parameter 10:21 [Rated Amps]. If the application can never reach
full speed, it is an indication that the motor and/or the drive may be undersized for the application. Contact your
Local distributor or Rockwell Automation technical support for further application review, or potential drive sizing
considerations.
Deceleration Time
If the drive faults on either an overload (F10003 or F10028), or an overvoltage (F10107) fault condition during
deceleration, it is likely due to the deceleration time being too short for the system, which results in the fault condition.
There are two ways to eliminate the fault condition:
• The drive can be set to coast to rest (parameter 10:110 [Mtr Stop Mode A] set = 0 'Coast').
• The deceleration time can be increased (parameter 10:1917 [VRef Decel Time 1] set to a larger value).
Set parameter 10:1917 [VRef Decel Time 1] to the longest necessary deceleration time allowed by the system. If drive
faults or DC bus overvoltage conditions continue to exist, dynamic braking can be required.
PowerFlex® 755TR regenerative drives are capable of regeneration to the AC line and should not require dynamic
braking.
PowerFlex 755TL low harmonic AC drives do not have regeneration capability and may benefit from the addition of a
dynamic brake resistor. See PowerFlex Dynamic Braking Resistor Calculator, publication PFLEX-AT001
, to understand
how to apply a dynamic brake to the application.
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