Lenze 8400 protec Manual - Manual (Page 148)

Braking operation
Braking operation without additional measures
9
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148 EDS84DPS424 EN 5.0
9 Braking operation
When electric motors are braked, the kinetic energy of the drive train is fed back to the DC
bus in generator mode. This energy results in an increased DC−bus voltage. Various
strategies are available to avoid an overvoltage in the DC bus:
ƒ Braking operation without additional measures
This includes functions integrated in the controller which do not require external brake
resistors and can be parameterised using the »Engineer«:
– DC injection brake DCB
– Stopping of the ramp function generator
– "Inverter motor brake" function (from software version 01.01)
The braking operation without external brake resistor is suitable for simple
applications which do not require strict compliance with the deceleration ramp. Hence,
this is a cost−saving procedure since a brake resistor is not required. A combination of
all above−mentioned braking procedures is also possible, e.g. to perform emergency
braking in the event of a brake resistor failure.
ƒ Braking operation with external brake resistor
ƒ Braking operation with spring−applied brake
(
Stop!
ƒ The two braking procedures "Stopping of the ramp function generator" and
"Inverter motor brake" are only active in speed−controlled applications if the
position controller does not interfere!
ƒ Do not additionally adapt the motor load (I2xt) if the inverter motor brake is
used!
In this case, the motor may thermally overload or the motor overload
monitoring (I2xt) may be working incorrectly!
9.1 Braking operation without additional measures
DC injection brake DCB
To decelerate small masses, the "DC injection brake DCB" function can be parameterised.
DC−injection braking enables a quick deceleration of the drive to standstill without the
need for an external brake resistor.
ƒ Code C00036 can be used to select the braking current.
ƒ The maximum braking torque to be realised by the DC braking current amounts to
approx. 20 ... 30 % of the rated motor torque. It is lower compared to braking action
in generator mode with external brake resistor.
ƒ Automatic DC−injection braking (Auto−DCB) improves the starting performance of
the motor when the operation mode without speed feedback is used.
Further information on the relevant parameters can be obtained from the software
manual.