Lenze E84DSxxx - Manual (Page 315)

Lenze · 8400 protec StateLine · Reference manual · DMS 4.2 EN · 03/2013 · TD05
315
8 Basic drive functions (MCK)
8.4 Holding brake control
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
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 ( 317)