8
05.01
8.13 Operation when the power fails
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Siemens AG 2012 All Rights Reserved
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
8.13
Operation when the power fails
8.13.1
Application and mode of operation
The function ”operation with the power fails” (power failure buffering) is used, for
example, for machines where personnel could be in danger or significant ma-
chine damage could occur due to a danger of collision when machining due to
power failure or for internal control fault signals. Further, the function is used for
machines with complex machining operations. For example, when machining
gear wheels (hobbing, roller grinding) where expensive tools and workpieces
are used and which should be protected from possible damage if power failures
were to occur.
For operation when the power fails, stopping and/or retracting drive motion, the
energy stored in the capacitors of the power DC link and the kinetic energy of
the moved masses stored when the drives regenerate into the line supply can
be briefly used. To do this, a connection must be established from the power DC
link P600/M600 to the auxiliary power supply via the terminals P500/M500 in
the NE module or in the monitoring module.
Further, additional circuit measures are required. For example, the control volt-
ages must be buffered and a power failure and/or DC link monitoring function to
initiate the appropriate control functions.
After a hazard analysis, the machinery construction OEM must evaluate these
risks and requirements and apply appropriate
measures to avoid such hazards or damage.
The requirements placed on the power failure concepts differ significantly de-
pending on the user and machine and must therefore be individually engine-
ered.
8.13.2
Functions
An essential criterion when implementing power failure concepts is to be able to
quickly detect a line supply fault (power failure, line supply undervoltage or
phase failure).
When a line supply fault occurs, the DC link voltage quickly dips/fails due to the
power drawn by the drives and the connected power supplies for the drive and
control components. The discharge time depends on the DC link capacity, the
charge (voltage) and the loading after the power failure.
Operation when the power fails with initiation of the regenerative feedback of
one or more drives into the DC link must become effective before the DC link
voltage decreases below the rated voltage, e.g. 600 V DC to 350 V DC. At
approx. 350 V, the pulses are internally inhibited in the drive group, and the
drives coast down.
The DC link voltage of 600 V DC is proportionally emulated at the control level
and can be evaluated in the 611 digital and 611 universal control units via the
equipment bus. The DC link voltage can be monitored to provide a fast re-
sponse using parameterizable limit value stages, e.g. to 450 – 500 V. This
therefore allows indirectly, an immediate response to be made to a line supply
fault, e.g. power failure.
8 Important Circuit Information
05.08
