PACMotion™ PSD Installation and User Manual
Section 4
GFK-3168A
September 2020
Technical Description and Data
22
4.14
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 PSD 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 PSD uses dynamic braking depends on (
DRV.DISMODE
).
4.14.1
Regen circuit
When the amount of returned energy builds the bus capacitor voltage up enough the drive
activates the regen circuit to start dumping the returned energy in the regen resistor (also called
regenerative or brake resistor). This resistor could be internal or connected external to the drive,
depending on drive model and drive wiring.
4.14.1.1
IC830DP00306 to IC830DP00606
No internal regen resistor. Depending on the application requirements, an external resistor can be
connected.
4.14.1.2
IC830DP01206 to IC830DP02406 and IC830DP00307 to
IC830DP02407
With internal resistor plus the ability to connect an external resistor depending on the application
requirements.
External regen resistors are described in the GFK-3173,
PACMotion PSD Accessories Manual
.
4.14.2
Functional description
When the amount of returned energy builds the bus capacitor voltage up enough the drive
activates the brake chopper to start dumping the returned energy in the regen resistor.
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 regen power rating, the drive generates the warning "n521 Regen Over
power”.
If the
power increases past the fault level, the regen circuit will switch off.
With the regen circuit switched off, the drive internal DC bus link voltage is supervised. 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
“F501
Bus Over voltage" (
➜
# 197). The Fault
contact (terminals X8/9-10) is opened (
➜
# 161) due to this fault.
Several drives coupled through the DC bus link (+DC, -DC)
Using the built-in regen circuit, several drives of the same series can be operated from a common
DC-bus link (
# 108), without any additional measures. 90% of the combined power of all the
coupled drives is always available for peak and continuous power. The switch-off on over voltage
