4.1.4 Regenerative energy
An electric motor can act as a generator when gravity effects or deceleration drive the motor in generator
mode and power is injected into the power line. The amount of regenerated energy is relative to the
mechanical energy. Higher deceleration and higher inertia can cause more regenerated power. The
regenerated energy can cause overvoltage on the DC link which poses a dangerous situation for all
equipment on the shared bus. It is essential to prevent overvoltage for the system to work correctly. The
regenerative energy can be either absorbed by a battery (e.g. in an AGV) or burnt by resistors (braking
chopper or shunt).
4.1.4.1 Estimation of regenerated energy
The regenerated energy is related to the mechanical energy. Load, gravity and deceleration are important
parameters to define the amount of regenerated energy:
with:
: mechanical energy
: kinetic energy
: potential energy
To estimate the DC bus capacitor and braking resistor:
1. Calculate the amount of regenerated energy.
2. Calculate the maximum capacitor using the overvoltage protection level.
3. Calculate the dissipated energy.
4. Calculate the amount of power that needs to be dissipated by the braking chopper.
4.1.4.2 Braking chopper
A braking chopper (or other shunt circuit) is used to burn the energy that can’t be recuperated. It is
recommended to use SOMANET drives together with one or multiple SOMANET Braking Chopper 48V 500W.
For more information, please refer to
SOMANET Braking Chopper 48V 500W
.
The number of braking choppers depends on the amount of excessive energy (for peak power) and the
frequency of regeneration (thermal load).
The SOMANET Braking Chopper is protected against overvoltage and overcurrent. In both cases of overload
the chopper will switch off, which will lead to an overvoltage fault on the drive.
Attention
This can lead to dangerous situations if the robot isn’t able to decelerate as necessary.
Synapticon Documentation
© 2021 Synapticon GmbH | Daimlerstraße 26 | D-71101 Schönaich Documentation v 4.19.0 | Built 2022-02-01
971/1031
