AKD2G-S Installation, Safety 1 | 6 Technical description and data
6.8 Electrical Motor Braking
6.8.1 Dynamic Braking
Dynamic braking is a method to slow down a servo system by dissipating the mechanical
energy driven by the motor back EMF.
Dynamic braking is not functional safe..
The AKD2G has a built in advanced dynamic braking mode which operates fully in hardware.
When activated, the drive shorts the motor terminals. This forces all of the dynamic braking
current to be stopping current and insures the fastest stopping per ampere 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
AXIS#.DBILIMIT
parameter to insure that the drive, motor, and customer load do not see
excessive currents/forces.
Whether and how the AKD2G uses dynamic braking depends on (
AXIS#.DISMODE
).
6.8.2 Rheostatic energy dissipation
When the amount of motor back EMF builds the bus capacitor voltage up enough the drive
activates the rheostatic regenerative circuit to start dumping the returned energy in the regen
resistor (also called regenerative resistor or brake resistor). All AKD2G offer internal resistor
plus the ability to connect an external resistor depending on the application requirements.
External regen resistors are described in the regional
Accessories Manual
.
6.8.2.1 Functional description
1. Individual drives, not coupled through the DC bus link circuit (+DC, -DC)
When the energy fed back from the motor has an average or peak power that exceeds the pre-
set level for the brake power rating, the drive generates the warning "W2010 Regen Energy
Critical”. If the power exceeds the set fault level, the regenerative circuit will switch off.
2. Several drives coupled through the DC bus link (+DC, -DC)
Using the built-in regenerative circuit, several drives of the same series can be operated from
a common DC-bus link (
# 75), without any additional measures. 90% of the combined
power of all the coupled drives is always available for peak and continuous power. If the
power of the drive with the lowest switch-off threshold (resulting from tolerances) exceeds
the set fault level, the regenerative circuit will switch off.
Switch-off on over voltage
: With the regenerative circuit switched off, the DC bus link
voltage is not dissipated and therefore the level increases. The drive 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 “F2006 Bus Over voltage". The ready to operate con-
tact (terminals X21/B5-B6) is opened (
Observe the regeneration time (some minutes) after full load with peak brake power.
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Kollmorgen | kdn.kollmorgen.com | Beta, December 2018
