8400 StateLine C | Reference manual
Basic drive functions (MCK)
Holding brake control
372
L
Firmware
≤
11.00 - DMS 8.0 EN - 10/2011
8.4.2.5
Ramp time for approaching the setpoint speed
For the "
Speed follower
" operating mode, a ramp time can be set in
C02610/1
if the
setpoint is already out of reach while the holding brake is initiating the feedforward
control process.
Example:
A setpoint of 90 % is selected via the ramp function generator while the brake is applied
(controller is inhibited).
1. At the set ramp (in most cases
C00012
), the ramp function generator ramps up to 90 %.
2. The brake identifies the setpoint selection of 5 % (release switching threshold). The
feedforward control of the brake provides 3 % of the setpoint and will not report the
release of the brake after approx. 1 s has expired.
Conclusion: 90 % of the selected setpoint is already ramped up while the brake is only
providing 3 % of the setpoint via the feedforward control.
Since at this point a step change from 3 % to 90 % may cause mechanical jerks, the setpoint
is ramped up from 3 % to 90 %, using the ramp time set in
C02610/1
(Lenze setting: 2 s).
This example is based on the V/f characteristic control mode (VFCplus). The ramp process
to the "elapsed" setpoint, however, is valid for all control modes of the motor control as
there is always a mechanical and/or electrical delay when the holding brake is activated.
This delay is due to:
Motor magnetisation (in the case of servo control only)
Mechanical delay of all switching elements connected upstream to the holding brake
Mechanical delay of the holding brake itself
Generation of the holding torque by the motor
Related topics:
Process when brake is released
(
374)
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