7.10 Dynamic Braking
Dynamic braking is a method to slow down a servo system by dissipating the mechanical
energy driven by the motor back EMF. The AKD-N has a built in advanced dynamic braking
mode which operates fully in hardware. When activated, the drive shorts the motor terminals
in phase with the back EMF (q axis) but continues to operate the non-force producing current
loop (d-axis) with 0 current. This forces all of the dynamic braking current to be stopping cur-
rent and insures the fastest stopping/amp of motor terminal current.
When current is not being limited, the mechanical energy is being dissipated in the motor
resistance.
When current is being limited, energy is returned to the drive bus capacitors.
The drive also limits the maximum dynamic braking motor terminal current via the
DRV.DBILIMIT
parameter to insure that the drive, motor, and customer load do not see
excessive currents/forces.
Whether and how the AKD-N uses dynamic braking depends on (
DRV.DISMODE
).
7.11 Regen circuit
When the amount of returned energy builds the bus capacitor voltage up enough the AKD-C
activates the regen circuit to start dumping the returned energy in the regen resistor (also
called regenerative or brake resistor). The AKD-C has an internal regen resistor is resistor, an
additional external one can be connected to X14.
External regen resistors are described in the regional
AKD Accessories Manual
.
7.11.1 Functional description
When the amount of returned energy builds the bus capacitor voltage up enough the AKD-C
activates the brake chopper to start dumping the returned energy in the regen resistor at the
AKD-C (internally or connected to terminal X14).
90% of the combined power of all the coupled drives is always available for peak and con-
tinuous power.
Switch-off on over voltage
The drive that has the lowest switch-off threshold (resulting from tolerances) reports an over-
voltage fault if the DC bus threshold is exceeded. The drive power stage is disabled and the
load coasts to a stop with the fault message “F501 Bus Over voltage". The AKD-C fault relay
contact (terminals X15/5-6) is opened due to this fault.
7.11.2 Technical data
Technical data are listed in the
AKD -C Installation Manual
.
AKD-N Installation | 7 Technical description and data
Kollmorgen | kdn.kollmorgen.com | February 2018
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