Set oscillation damping
The oscillation damping serves to reduce the oscillations during no-load operation
which are caused by energy oscillating between the mechanical system
(mass inertia) and the electrical system
(DC bus). Furthermore, the oscillation damping can also be used
to compensate for resonances.
Preconditions
The function is only effective in the motor control type "V/f characteristic control (VFC open loop)".
Restrictions
Observe the following restrictions:
–
Damping is possible only for constant oscillations at a steady-state
operating point.
–
Oscillations occurring sporadically cannot be damped.
–
Oscillation damping is not suitable for oscillations occurring during dynamic processes
(e.g. accelerations or load changes).
–
Oscillation damping is only active if the setpoint speed is greater than 10 rpm and the
DC-bus voltage exceeds a value of 100 V.
Details
The determination of the oscillation is based on the active current. In order to obtain the alternating component
of the active current, this current is differentiated. This signal is then passed through a
PT1 filter.
Identification of the oscillation
Before the oscillation damping function can be parameterised, the oscillation has to be identified.
One way to do this is to examine the motor current while oscillation damping
is switched off (gain = 0 %). At steady-state operation, a constant current flows. If the drive oscillates, these oscillations are also visible on the motor current. It is therefore possible to determine the
frequency and the amplitude of the oscillation from the alternating component of the motor current. In the
following, this alternating component is referred to as "current oscillation".
Parameter setting
Set the gain of the oscillation signal according to the following equation:
0x2B0A:001 (P318.01) = current amplitude * 100 % / (
Ö
2 * maximum device current)The default time constant of the PT1 filter is sufficient for most applications. If required, it is only possible to adapt the time constant via »EASY Starter«. Generally, the time constant must be set so that the oscillation is dampened and higher-frequency components are filtered from the signal. The time constant
is given by the reciprocal value of double the current oscillation frequency:
0x2B0A:002 (P318.02) = 1 / (2 * oscillation frequency)
Parameter