KEB COMBIVERT F5-A, Руководство по применению, Страница: 264 / 552

Page 7.10 - 4 COMBIVERT F5-A, -E, -H © KEB, 2012-10
Current control, -limiting and switching frequencies
7.10.2. Current limit
The hardware current limit becomes active if the phase current exceeds the value of In.18 „hardware current“.
Through short-time power shutdown the current limit can eliminate short current peaks at low speeds, e.g.
when starting the motor.
However if the current level is exceeded at high speed under load, disconnection of the voltage leads to a red-
uction of the breakdown torque of the motor and thus to a "fall back" of the motor. Additionally the motor model
is falsified. Therefore this function should be switched off for controlled drives.
Attention: The hardware current limitation limits the current at the maximum and triggers no error. This can lead
to torque sags at the motor shaft. This function is very critical especially during operation "lifting and lowering".
The drive may sag due to missing torque without brake engage.
The only exception: in speed-controlled operation with encoder feedback without motor model, current
overshoots can occur during the start if the current controller are not optimally adjusted. They can be compen-
sated by uF.15 = 1: „single-phase mode“. The hardware current limiting makes sense also at controlled drives.
uF.15: Hardware current limit
Value Explanation
0 Off: recommended adjustment for closed-loop operation
1 Single-phase mode: Limits the current reliable, but deep sag in the current
2 Zero vector mode: Lower current sag, but overcurrent errors can occur in rare cases.
The software current limiting should be used instead of the hardware protective function. The maximum permis-
sible current must be entered in parameter dr.37.
It is reasonable to enter the hardware current level (In.18) here if the application does not require another value.
The function is activated by setting "current/torque mode = 1:on" in parameter (ds.03) "current/torque mode.
dS.03: current/torque mode
Bit Meaning Value Explanation
0 Maximum current mode
0: off
1: on Activation of the software current limiting