Function library
Function blocks
9.2.41 Mains failure control (MFAIL)
9-154
L
EDSVS9332S-D11 EN 3.0
9.2.41.3 Restart protection
The integrated restart protection is to avoid a restart in the lower speed range, after the supply voltage
was interrupted for a short time only (mains recovery before the drive has come to standstill).
z How to protect the drive from a restart is explained in chapter 9.2.41.2.
z Go to C0472/18 and enter the threshold in [%] of nmax (C0011) if you do not want an
automatic restart below this threshold after mains recovery.
– Speed after mains recovery < threshold in C0472/18: Drive is still braked in a controlled way.
This function can only be completed by MFAIL-RESET = HIGH.
– Speed after mains recovery > threshold in C0472/18: Drive accelerates to its setpoint along
the set ramps.
z The function is deactivated by:
– C0472/18 = 0 % or
– C0975 = 1000 (FIXED0% to MFAIL-THRESHLD)
z Reset with MFAIL-RESET = HIGH
– is required after every mains connection
– is displayed by MFAIL-STATUS = HIGH, if MFAIL-FAULT = LOW
9.2.41.4 Reset of the mains failure control
z The mains failure control is reset with MFAIL-RESET = HIGH (in the example with terminal
X5/ E5).
z The reset pulse is always required if:
– the restart protection is active.
– the restart protection is used and the supply (mains or DC supply) was switched on.
9.2.41.5 Dynamic adaptation of the control parameters
In special cases, a dynamic modification of the proportional gain may be useful. For this, two inputs
(MFAIL-CONST and MFAIL-ADAPT) are available at the function block MFAIL. The resulting
proportional gain results from:
V
p
= C0980 ⋅
MFAIL-CONST − |MFAIL-ADAPT|
100 %
9.2.41.6 Fast mains recovery (KU)
The fast mains recovery causes a restart of the controller unless the restart protection is active. The
drive accelerates to its setpoint. If this is not wanted, the restart can be delayed via the retrigger time
C0983, or avoided together with the restart protection.
A fast mains recovery occurs:
z due to the system, the mains recovery is indicated by the mains failure detection via the level
of the DC bus voltage (see Chapter 9.2.41.1).
z because of a ”short interrupt” (KU) of the utility company (e.g. in case of thunderstorms)
z because of faulty components in the supply cables (e.g. slip rings)
Set the retrigger time C0983 higher than the measured deceleration time during braking.
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