12
Project planning
Notes on the supply
Operating Instructions – Compact Extra-Low Voltage Drives
83
12.4
Notes on the supply
12.4.1
Dimensioning the DC 24 V supply
The required power of the
DC 24
V supply depends on the number of connected
drives and their current consumption.
The current demand of an individual drive is a combination of the basic current con-
sumption of the electronics and the current consumption of the used options (e.g.
brake).
For more information, see chapter "Technical data".
12.4.2
Dimensioning the DC 48 V supply
The
DC 48
V supply must provide the power that is required at the output shaft of the
drive. Determine the maximum power demand observing the efficiency.
A power supply unit with a rated power of
500
W enables operation within the rated
range. In the event of dynamic capacity utilization, the power demand can be signifi-
cantly higher for a short time.
For more information, see the chapter "Technical Data".
12.4.3
Regenerative operation
In regenerative operation (braking operation) of the drive, energy is fed into the
DC 48
V supply circuit. This results in an increase in the supply voltage at the drive
and at the output of the
48
V power supply unit. The compact extra-low voltage drive
does not limit the voltage increase until the supply voltage exceeds the switch-on
threshold of the brake chopper.
Switched-mode power supplies are equipped with output voltage monitoring. If the
output voltage that is present at the power supply unit exceeds the value of the
device-dependent switching threshold, this can lead to the voltage supply being
switched off. The drive is no longer supplied with
48
V and signals a failure. Further
operation is only possible after a reset.
You can install a diode to avoid the possible regenerative voltage rise at the output of
the
48
V power supply unit and the resulting switch-off. Dimension the diode according
to the currents and the voltage of the
48
V supply. Install the diode in the U
DC48
48
V
supply as shown in the following figure:
BN
BK
GND
U
DC48V
Compact extra-low
voltage drive
28608492811
Industrial switched-mode power supplies have back-feeding protection. Back-feeding
protection specifies how high the voltage may be at the output during regenerative
operation of the drive without the power supply being switched off or damaged. Please
observe the information on the power supply data sheet.
If the voltage value of the back-feeding protection is higher than the switch-on
threshold of the brake chopper, a diode does not need to be installed.
During braking operation of the drive, the energy that is fed back is dissipated via an
optional braking resistor.
26718014/EN – 11/2020
