Appendix; Discharging Of Capacitors; Discharging Of Dc Bus Capacitors; Discharging Device - Bosch Rexroth IndraDrive Mi Project Planning Manual

Project Planning Manual | Rexroth IndraDrive Mi
14

Appendix

14.1

Discharging of Capacitors

14.1.1

Discharging of DC Bus Capacitors

14.1.2

Discharging Device

Operating Principle

In the drive system Rexroth IndraDrive, capacitors are used in the DC bus as
energy stores. In drive controllers and particularly in supply units, such capac‐
itors have already been integrated.
Energy stores maintain their energy even when the supply voltage has been
cut off and have to be discharged before somebody gets in contact with them.
Discharging devices have been integrated in the components of the drive sys‐
tem Rexroth IndraDrive; within the indicated discharging time these devices
discharge the voltage below the allowed 50 V.
If additional capacitors (such as DC bus capacitor units) are connected, these
capacitors, too, have to be discharged before somebody gets in contact with
them.
Due to the operating principle, the discharging time is the longer
● the bigger the energy store (the capacitance value)
● the higher the voltage to which the energy store has been charged
● the greater the resistance for discharging the capacitors
Components of the drive system Rexroth IndraDrive have been dimensioned
in such a way that after the supply voltage was cut off, the voltage value falls
below 50 V within a discharging time of a maximum of 30 minutes.
To shorten the waiting time until voltage has fallen below 50 V, you can take
the following measures:
● When using HMV01 supply units: activate the function "ZKS" (DC bus
short circuit)
● Use the discharging device described below.
A contactor is installed to switch a resistor to the terminals L+ and L- of the DC
bus connection to discharge the capacitors. The contactor is activated via a
control input which is supplied with appropriate control voltage.
R discharging resistor
K contactor contact
Fig.14-1: Operating principle of discharging device
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Appendix