Lenze DSD - Manual (Page 183)

Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
183
7 Applications
7.21 Dimension the multi-axis system
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7.21 Dimension the multi-axis system
Electrical drives are frequently accelerated and braked. Then, electrical energy is converted into ki-
netic or potential energy which is partly fed back in the braking or lowering process. This recovered
energy is often converted into heat via a brake resistor and is then lost unused.
Often, it is well worth passing on this braking energy for another use, thereby improving energy ef-
ficiency. In a multi-axis system, the brake energy can be used completely under ideal conditions.
7.21.1 Using braking energy
If one or several inverters of a multi-axis system operate in generator mode (braking operation), the
generated energy is transmitted to the common DC bus or the DC voltage source. Thus, the energy
is available for the inverters in the multi-axis system that operate in motor mode.
Advantages:
• Smaller dimensioning of the power supply module or regenerative power supply module.
• Generally, the use of a central braking unit is sufficient.
• Less energy is taken from the three-phase system.
• The number of mains input modules and the connected expense (e.g. for wiring) can be optimal-
ly adapted to the application.
• For Servo Drives 9400 and i700 with central supply, the wiring complexity is minimal.
• The multi-axis system is the most cost-effective version to use recovered energy.
Operation in generator mode with power recovery into the mains
[7-178] Operation in generator mode with power recovery into the mains
• For power recovery into the mains, inverters must be connected to a regenerative power supply
module via the DC bus.
• The use of a regenerative power supply module may be economically reasonable if the drive
power exceeds 5 kW.
P
gen
Power recovery into the mains
P
th,I1
Inverter: Power loss of rectifier
P
th,I2
Inverter: Power loss of inverter
P
th,M
Power loss in motor
P
gen,mec
Mechanically generated power by braking processes
~
=
P
gen,mec
P
th,M
P
th,I2
P
th,I1
P
gen
3 AC M
3~
~
=