10.15.1. Activating the mains failure control
1. Set the selection "Enabled [1]" in 0x2D66:001 (P721.01).
2. Set the activation threshold in [%] with reference to the nominal DC-bus voltage in
0x2D66:002 (P721.02).
• Recommended setting: 5 ... 10 % above the error threshold for undervoltage
(display in 0x2540:003 (P208.03)).
3. Set the voltage setpoint onto which the DC-bus voltage is to be maintained in
0x2D66:005 (P721.05).
• Recommended setting: 95 ... 100 % (of the nominal DC-bus voltage).
The mains failure control gets active with these settings if the DC-bus voltage falls below
the activation threshold. The DC-bus voltage controller now generates the required
operational energy from the rotational energy of the motor. The motor is decelerated by
the mains failure control. Thus, the deceleration ramp is shorter than the one of a non-
guided system (coasting drive).
After the mains failure control has been activated:
1. The DC-bus voltage is controlled with the acceleration time set in 0x2D66:006
(P721.06) to the setpoint set in 0x2D66:005 (P721.05).
2. An internally generated frequency setpoint is transferred to the motor control which
enables the motor (via the frequency setpoint) to be decelerated to a frequency close
to "0 Hz".
Starting value for the guided deceleration is the current output frequency.
The deceleration ramp (and hence the braking torque) results from the moment of
inertia of the load machine(s), the power loss of the drive (system) and the set
parameterisation.
Behaviour after mains recovery
If, after mains recovery, the DC-bus voltage has exceeded the activation threshold
(+hysteresis) again, an internal timing element is started. After the time period set in
0x2D66:007 (P721.07) has elapsed, the mains failure control is stopped if the restart
protection is not activated (default setting).
Restart protection
318
Fast mains recovery
318
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