Page 7.5 - 30 COMBIVERT F5-A, -E, -H © KEB, 2012-10
Motor data and controller adjustments of the asynchronous motor
dS.18: Model adaption
Bit Meaning Value Explanation
2
Model switch-
off
0: activated
4: deactivated
Deactivate switching to the frequency driven, current-controlled
operation
To utilise the open-loop mode for stopping, but, on the other hand, avoid negative effects during reversal, the
inverter must be programmed by way that stopping of the motor always follows in the same set.
Then, one can let the switch to the open-loop mode be activated for this set (the stop-set) (dS.18 = 0), and avoid
interfering effects during reversal for other sets with dS.18 = 4.
The, it is only necessary to ascertain that the range of low frequencies is traversed quickly.
This can be achieved by suitably setting parameter "ASCL start ramp time" (dS.22) and parameter "ASCL start
ramp speed" (dS.21), which apply to acceleration as well as deceleration.
ASCL / constant run with low speeds
Speed setpoints lying within the critical range must be avoided.
To avoid continuous operation in low frequency range, the minimum setpoint (oP.06 / oP.07) should be set to
speeds outside the critical range.
Alternatively, too-small setpoints may also be masked by parameter oP.65...oP.68 (blocked setpoints).
7.5.2.4.2 Switch to consecutive motor
If the motor still rotates when switching the modulation (e.g. "coast down" after malfunction) the calculation of
the actual speed can become unstable due to the motor model.
Therefore, if there is a risk that the motor has not reached speed 0 for the start, there are two alternative starting
methods:
speed search (Pn.26) or DC braking (Pn.28 / Pn.33)
During speed search, the drive attempts to determine the current speed via its mathematical model. The ope-
ration corresponding to the setpoint settings is re-established starting at this speed. For many standard motors,
this type of addition can be used.
For some motors or applications, e.g., for spindles, application of the speed search will be unsuccessful. In
these cases, speed is calculated incorrectly, the drive can vibrate, or the inverter can malfunction.
In these cases, the motor must be stopped by DC braking before the drive can be restarted. During DC braking,
a DC voltage is connected to the motor´s clamps. The small braking torque while the motor is still running at
high speed is a disadvantage.
For more (appropriate parameters, settings, etc.) see in 7.13.4 speed search and 7.15.1 DC braking, respec-
tively.
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