Internal Pretorque - KEB COMBIVERT F5 Reference Manual

5.12.2 Internal
Pretorque
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Internal pre-torque is a feature of the drive that can be used to minimize, if
not totally eliminate, the rollback which may occur at brake pick, without the
need for external load weighing devices. Pretorque is available when the
LC01 Control Mode is set for Closed Loop FOC or Closed Loop Synthetic
Pretorque.
Adjust the brake spring tension, brake voltage, and brake timing
first. Note that it is often advantageous to use a lower spring tension
and lower brake pick voltage to provide a softer lifting of the brake.
This allows for a smoother transition from brake to motor. It should
be noted that any subsequent changes to the brake could require
readjustment of the pre-torque.
The pre-torque is active at the beginning of a run, according to the timer
parameters LT02-03. When a run command has been given by the
controller, the drive will first perform a brief phase current check of the
motor before attempting to run. Upon successful completion, it is safe
to pick the brake and the LT02 Control Hold Off timer begins. During the
LT02 Control Hold Off period, the speed gains are held low to prevent any
disturbances under brake. After the LT02 Control Hold Off timer expires, the
pre-torque period becomes active and the LT03 Speed Start Delay timer
becomes active. The LT02 Control Hold Off timer should be set such that it
expires briefly before the brake is picked so the pretorque period before the
speed profile begins, LT03 Speed Start Delay, is active when rollback would
occur.
During the pre-torque period, the corresponding speed gains for pretorque,
LC05 KP Speed Pretorque and LC10 KI Speed Pretorque, are active; These
can be adjusted generally by increasing LC10 in steps of 1000. Typical LC10
ranges between 10,000 - 20,000. After the LT03 Speed Start Delay timer
has expired, the pretorque period expires, the acceleration begins and the
corresponding speed gains for acceleration and high speed are now active.
For control modes which dictate the speed profile and when it begins (i.e.
analog or serial) the pretorque period will expire as the acceleration begins.
For the best adjustment, delay the start of the run profile by
either delaying the pattern with LT02,LT03 (binary, digital,...) or
via the controller for external speed command (serial, analog,...).
The suggested delay is 2 seconds. This will allow the brake to
pick, rollback to occur, and a stabilized hold at zero speed before
acceleration. This will help assess the amount of rollback and timers
can be reduced for normal timing sequence after synthetic pretorque
has been optimally adjusted.
Initial Startup
105