Protective functions
© KEB, 2012-10 COMBIVERT F5-A, -E, -H Page 7.13 - 27
7
DC link voltage-dependent ramp stop
The LD-Stop (U) function can be used to prevent overvoltage errors during deceleration.
During deceleration energy is refeed into the frequency inverter, which causes a rise of the DC-link voltage.
If too much energy is recovered, the inverter can switch to overvoltage (OP) error.
If the LD-Stop (U) function is activated with Pn.22, the DEC ramp is stopped if the actual DC link voltage (ru.18)
exceeds the adjusted LD voltage (Pn.25).
Pn.25: LD voltage
Value Explanation
200V...1200V DC-link voltage level at which the ramp is stopped
Overvoltage errors cannot always be securely prevented with this protection function, because after setting
the ramps and the speed controller, further deceleration can occur despite stopping the ramp. If the drive
decelerates, e.g., at the torque limit, and can therefore not follow the ramp, it does not help to stop this ramp.
An undershoot of the speed controller due to a sudden termination of the ramp can also lead to further energy
recovery in the DC link.
Generally, the deceleration process is slowed down by this protection function. The use of a braking resistor is
necessary for a dynamic deceleration.
Ramp stop dependent on a digital input
With Pn.23 "ramp stop input selection", a digital input can be selected for triggering the ramp stop.
This input is only active if the stop for the corresponding ramp is permitted in Pn.22.
7.13.9 Electronic motor protection
Functional description for F5A-M and F5H-M
The motor protection function protects the connected motor against thermal destruction caused by high cur-
rents. The function corresponds largely to mechanical motor protection components, additionally the inuence
of the motor speed on the cooling of the motor is taken into consideration. The load of the motor is calculated
from the measured apparent current (ru.15) and the adjusted rated motor current (dr.12).
The following tripping times (VDE 0660, Part 104) apply for motors with separately driven fan or at rated fre-
quency of a self-ventilated motor:
1,2 • I
n
⇒ 2 hours
1,5 • I
n
⇒ 2 minutes
2 • I
n
⇒ 1 minute
8 • I
n
⇒ 5 seconds
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