Siemens SINUMERIK 840D sl Function Manual page 377

DC link energy
The energy available in the DC link of the drive units when the line supply fails is calculated
as follows:
This energy is available for a minimum time of t
Example
ALM with P
• C = C
20% component tolerance (assumption)
• VDClink
• VDClink
This energy is available for a time t
• E = 432Ws
• P
• η = 0.9 (assumption)
The following table shows a summary of the values for various SINAMICS ALM (infeed units).
Nominal and minimum capacity are taken into account. The maximum possible capacitance
(charge limit) consists of the sum of the capacity of the ALM and the Motor Modules, as well
as the external auxiliary capacitors (to be provided by the user). The capacitance used as
basis in the table for the minimum energy-content (C
tolerance of -20% (worst case).
Special Functions
Function Manual, 09/2011, 6FC5397-2BP40-2BA0
E = 1/2 * C * (VDClink
E: Energy in Wattseconds [Ws]
C: Total capacity of intermediate circuit in Farad [F]
VDClink : DC link voltage below which an undervoltage is identified.
alarm
SINAMICS Parameter: r0296 + p0279
VDClink : Lower limit of the DC link voltage for safe and reliable operation,
min
taking into account the motor-specific EMF.
Note VDClinkmin > VDClinkoff
t = E / P * η
min n
E: Energy in Wattseconds [Ws]
t Buffer time in milliseconds [ms]
min
P Power in kilowatt [kW]
n
η Efficiency of the drive unit
= 16 kW (for 3-ph. 380 V AC)
n
- 20% = 6000µF - 20% = 4800 µF, with
max
= 550V (assumption)
alarm
= 350V (assumption)
min
E = 1/2 * 4800µF *((550V)
= 16 kW
n
t = 432Ws / 16kW * 0,9 = 24,3ms
min
2 2
- VDClink )
alarm min
:
min
2 2
- (350V) ) = 432Ws
, e.g. for retraction motion:
min
min
R3: Extended stop and retract
6.2 Control-managed ESR
) takes into account a component
377