3.14.1 14-1* Mains On/Off
Parameters for configuring mains failure monitoring and
handling. If a mains failure appears, the frequency
converter tries to continue in a controlled way until the
power in the DC link is exhausted.
14-10 Mains Failure
Options
[1] Ctrl. ramp-down
,
[2] Ctrl. ramp-down, trip
,
[5] Kinetic
back-up, trip
,
[7] Kin. back-up, trip w recovery
are not active when
the option
[2] Torque
is selected in
.
Option:
Function:
NOTICE
cannot be
changed while the motor is running.
is typically used
where very short mains interruptions (voltage
dips) are present. At 100% load and a short
voltage interruption, the DC voltage on the main
capacitors drops quickly. For larger frequency
converters, it only takes a few milliseconds
before the DC level drops to about 373 V DC,
and the IGBTs cut off and lose the control of the
motor. When mains is restored, and the IGBTs
start again, the output frequency and voltage
vector do not correspond to the speed/
frequency of the motor, and the result is
normally an overvoltage or overcurrent, mostly
resulting in a trip lock.
can be programmed to avoid this
situation.
Select the function according to which the
frequency converter must act when the
threshold in
parameter 14-11 Mains Fault Voltage
is reached.
[0]
*
No
function
The frequency converter does not compensate
for a mains interruption. The voltage on the DC
link drops quickly and motor control is lost
within milliseconds to seconds. Trip lock is the
result.
[1]
Ctrl.
ramp-
down
Control of the motor remains with the frequency
converter, and the frequency converter performs
a controlled ramp down from
parameter 14-11 Mains Fault Voltage Level
. If
is
[0] Off
or
[2] AC
brake
, the ramp follows the overvoltage ramping.
If
is
[1] Resistor
Brake
, the ramp follows the setting in
parameter 3-81 Quick Stop Ramp Time
. This
selection is useful in pump applications, where
the inertia is low and the friction is high. When
mains is restored, the output frequency ramps
the motor up to the reference speed (if the
14-10 Mains Failure
Options
[1] Ctrl. ramp-down
,
[2] Ctrl. ramp-down, trip
,
[5] Kinetic
back-up, trip
,
[7] Kin. back-up, trip w recovery
are not active when
the option
[2] Torque
is selected in
Option:
Function:
mains interruption is prolonged, the controlled
ramp down may bring the output frequency
down to 0 RPM, and when the mains is restored,
the application is ramped up from 0 RPM to the
previous reference speed via the normal ramp
up). If the energy in the DC link disappears
before the motor is ramped to 0, the motor is
coasted.
Limitation:
See the introduction text in
[2]
Ctrl.
ramp-
down,
trip
The functionality is the same as in option
[1] Ctrl.
ramp-down
, except in this option a reset is
necessary for starting up after power-up.
[3]
Coasting
Centrifuges can run for 1 hour without supply. In
those situations, it is possible to select a coast
function at mains interruption, together with a
flying start, which occurs when the mains is
restored.
[4]
Kinetic
back-up
Kinetic back-up ensures that the frequency
converter keeps running as long as there is
energy in the system due to the inertia from
motor and load. This is done by converting the
mechanical energy to the DC link and
maintaining control of the frequency converter
and motor. This can extend the controlled
operation, depending on the inertia in the
system. For fans, it is typically several seconds;
for pumps up to 2 s; and for compressors only
for a fraction of a second. Many industry
applications can extend controlled operation for
many seconds, which is often enough time for
the mains to return.
Parameter Descriptions
Programming Guide
MG33MP02
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