GE AF-650 GP Programming Manual page 79

Parameter Descriptions
3.9.1 SP-1# Line On/Off
Parameters to configure actions taken for Line Failures,
Input Fault, and Imbalance.
SP-10 Line failure
3 3
Option:
[0] No
function
*
[1] Ctrl.
Decel
[2] Ctrl.
Decel,
trip
[3] Coasting
78
Function:
SP-10 Line failure 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 drives it only takes a few milliseconds
before the DC level is down to about 373 V DC
and the IGBTs cut off and looses the control over
the motor. When the mains is restored, and the
IGBTs start again, the output frequency and
voltage vector does not correspond to the speed/
frequency of the motor, and the result is normally
an overvoltage or overcurrent, mostly resulting in
a trip lock. SP-10 Line failure can be programmed
to avoid this situation.
Select the function to which the frequency
converter must act when the threshold in
SP-11 Line Voltage at Input Fault has been reached.
SP-10 Line failure cannot be changed while motor
is running.
The frequency converter will not compensate for a
mains interruption. The voltage on the DC-link will
drop quickly and motor control will be lost within
milliseconds to seconds. Trip lock will be the
result.
The frequency converter will remain control of the
motor and do a controlled ramp down from
SP-11 Line Voltage at Input Fault level. If B-10 Brake
Function is [0] Off or [2] AC brake, the ramp will
follow the Over Voltage Ramping. If B-10 Brake
Function is [1] Resistor Brake the ramp will follow
the setting in C-23 Quick Stop Decel Time. This
selection is particularly useful in pump
applications, where the inertia is low and the
friction is high. When the mains is restored, the
output frequency will ramp the motor up to the
reference speed (if the mains interruption is
prolonged, the controlled ramp down might take
the output frequency all the way down to 0 RPM,
and when the mains is restored, the application is
ramped up from 0rpm to the previous reference
speed via the normal ramp up). If the energy in
the DC-link disappears before the motor is
ramped to zero the motor will be coasted.
This selection is similar to selection [1] except that
in [2] a reset is necessary for starting up after
power-up.
Centrifuges can run for an hour without power
supply. In those situations it is possible to select a
AF-650 GP Programming Guide
SP-10 Line failure
Option:
[4] Kinetic
back-up
DET-618C
Function:
coast function at mains interruption, together with
a flying start which occurs when the mains is
restored.
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 thereby
maintaining control of the drive 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 seconds 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.
Illustration 3.35 Kinetick Back-up
A Normal operation
B Mains failure
C Kinetic back-up
D Mains return
E Normal Operation: ramping
Table 3.17 Legend to Illustration 3.35
The DC-level during [4] Kinetic back-up is
SP-11 Line Voltage at Input Fault * 1.35.
If the mains do not return U is maintained as
DC
long as possible by ramping the speed down
towards 0 RPM. Finally the frequency converter
coasts.
If the mains return while in kinetic back-up U
will increase above SP-11 Line Voltage at Input
Fault*1.35. This is detected in one of the following
ways.
1. If U > SP-11 Line Voltage at Input
DC
Fault*1.35*1.05
2. If the speed is above the reference. This
is relevant if the mains come back at a
lower level than before, e.g. SP-11 Line
Voltage at Input Fault*1.35*1.02. This
does not fulfil the criterion in point one
and the frequency converter will try to
DC