User manual

88/164 Bosch Rexroth AG NYCe4000 Standard Housings and Accessories Manual
NY4930 Brake Unit
12.1 Introduction
When a motor is decelerated by the NYCe4000 motion control system,
mechanical energy is converted into electrical energy. This conversion is called
regeneration. A part of this regeneration energy is lost to friction in the mechanical
system, and converted into heat due to I
2
R losses in the motor windings, cabling
and drive module electronics. The rest of the regeneration energy is added to the
electrical energy already stored in the internal capacitors of the system (drive
power supply, drive module, optional installed capacitors). This regeneration
energy causes an increase of the voltage level of these capacitors. If too much
energy is added to the capacitors in the system, the drive voltage can increase to
a level where the over-voltage detection of the drive module will shut down the
drive. If the voltage level increases above the absolute maximum voltage rating,
damage to the drive power supply and/or the drive module may occur.
The Brake Unit is a standalone module in the NYCe4000 system. The Brake Unit
includes a capacitor to store regeneration energy, and has a control circuit that
shunts some of the regeneration energy into a resistor if the voltage level
increases too much. The Brake Unit is only needed in a system with NY4120
and/or NY4140 drive modules.
Three different models of the NY4930 are available to cover a wide range of drive
power supply voltages.
12.2 Functional description
The NY4930 has a large capacitor C at the input to buffer energy and filter
outgoing pulses. A user-selectable switch sets the factor for the drive voltage
divider. An internal circuit measures the temperature. The drive voltage and the
temperature are compared. The output of the comparator generates the so-called
dissipation signal, and this signal can turn the FET on and off. The regeneration
energy is dissipated in the high-dissipation resistor R when the FET is turned on.
See the (simplified) schematic in Fig. 76.
Fig. 76 Functional diagram of the NY4930
Two status signals are available to notify the system of the state of the Brake
Unit. One output provides the functional status, and the other output signals the
temperature status. The output signals are created with relay contacts and thus
electrically isolated. The output signals are also visible via LEDs on the Brake
Unit.