At a glance, continued, Overview, Determining when energy is absorbed – Schneider Electric Lexium 17S Series User Manual
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At a Glance, continued
Overview
When the drive is braking or decelerating a moving load, the kinetic energy of the
load must be absorbed by the drive. As the drive decelerates the load, this energy
charges the DC link capacitors to successively higher voltages. To prevent damage
to the internal electronics, a shunt regulator circuit will apply the Regen resistor
across the capacitors when the voltage rises to a set voltage level (determined by
the “Mains Voltage” parameter). This dissipates the remaining energy as heat in the
Regen resistor. The energy dissipated by the Regen resistor must be calculated in
order to determine the proper power rating of the resistor.
Determining
When Energy Is
Absorbed
To determine when the drive is absorbing energy, examine the motion profile (that
is, a graphical plot) of axis speed and torque applied to the motor. Whenever the
sign (+ or -) of the torque applied to the motor is opposite that of the speed, the
drive is absorbing energy. This typically happens when the drive is decelerating the
motor, the motor is controlling tension in a web application, or the motor is lowering
a mass in a vertical axis.