Functions/Power Loss - gefran ADV200 Manual

22.10 – FUNCTIONS/POWER LOSS
This function controls a loss of power or temporary mains failure.
When the function is enabled the system stops with the controlled ramp; the power regenerated by the load
sustains the DC link power supply so that the motor speed can be controlled. The speed of the motor is control-
led for as long as power can be recovered (motor speed almost zero but not zero), after which the Undervolt-
age alarm is generated and the motor performs an uncontrolled stop due to inertia.
The function is only effective with loads that accumulate sufficient energy (typically loads with a high moment of
inertia and which the moment the power loss occurs have a speed of rotation not close to zero). The function
cannot be used for passive loads.
The function can only be used with Regulation mode = Flux vector CL (asynchronous and synchronous mo-
tors) and Regulation mode = V/f control (asynchronous motors).
The Powerloss function is enabled when the DC link voltage falls below a threshold configured internally as a
function of the mains voltage at a value that is higher than the Undervoltage threshold. When the function is
enabled the drive controls a stop with a user-definable deceleration ramp. In this phase the current limit is con-
trolled by a regulator on the DC link voltage and the setpoint is a threshold configured internally as a function of
the mains voltage at a value below the Overvoltage threshold.
The regulator envisages two setting parameters (proportional and integral) calculated in advance by the drive
as a function of the size of the motor and plate data. If the regulator acts on the current limit the motor speed
does not follow the set deceleration ramp. The function continues for as long as power can be recovered,
after which the Undervoltage alarm is generated. If the mains supply is restored during the deceleration ramp
phase, the user can configure how the drive should behave. The following options are available: continue in
any case until reaching zero speed or stop the deceleration ramp and pass to the set reference.
The drive does not automatically recognise the fact that the mains supply has been restored. This information
must be supplied from the outside via the Powerloss mains src digital input.
The presence of the braking unit prevents the intervention of the Overvoltage alarm and the function has the
advantage of being able to stop the motor while guaranteeing the set time.
As the setpoint of the Powerloss function regulator is higher than the brake activation threshold, it is not enabled
and the current limit is not altered to allow compliance with the set deceleration ramp time. The intervention of
the braking unit dissipates the energy of the motor in the resistor, reducing the amount of power available to sus-
tain the DC link and the time available to control stopping of the motor. The presence of the braking unit could
mean that the speed of the motor from which no power can be recovered is higher than that with no braking unit.
The function can be used on machines with a single drive as well as on machines with several drives, the
speeds of which must always be synchronised.
For machines with a single drive, enabling the Powerloss function is sufficient.
For machines with several drives, the DC links must be connected: the Powerloss function must only be
enabled on the drive identified as the master and not on the slaves. The master drive is normally the one that
controls the load with the highest inertia. The master drive sends the Powerloss nextratio signal with the ratio
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ADV200 • Functions description and parameters list