Operating Instruction - Frequency Inverter 230V / 400V ... - opis.cz

16 Control FunctionsThe frequency inverters provide a selection of established control methods in Configuration30. The selected control structure can parameterized as required and optimizedfor the application by further functions.16.1 Intelligent current limitsThe current limits to be set according to the application avoid inadmissible loading ofthe connected load and prevent a fault switch-off of the frequency inverter. The functionextends the current controller available in the control system. The overload reserveof the frequency inverter can be used optimally by means of the intelligent currentlimits, in particular in applications with dynamic load alternations. The criterion tobe selected via the parameter Operation Mode 573 defines the threshold to the activationof the intelligent current limit. The parameterized rated motor current or thereference current of the frequency inverter is synchronized as the limit value of theintelligent current limits.Operation modeFunction0 - Off The function is switched off.1 - Ixt Limitation to the overload of the frequency inverter (Ixt)10 - Tc Limitation to the maximum heat sink temperature (T C )11 - Ixt + Tc Operation mode 1 and 10 (Ixt + T C )20 - Motor Temp. Limitation to the motor temperature (T Motor )21 - Motor Temp.+ Ixt Operation mode 20 and 1 (T Motor + Ixt)30 - Tc + Motor Temp. Operation mode 10 and 20 (T C + T Motor )Tc + Motor Temp.31 -+ IxtOperation mode 10, 20 and (T C + T Motor + Ixt)The threshold value selected via the parameter Operation Mode 573 is monitored bythe intelligent current limits. In the operation modes with motor and heat sink temperaturemonitoring, the reduction of power selected with the parameter Power Limit574 is done when the threshold value has been reached. This is achieved by a reductionof the output current and the speed in motor operation. The load behavior of theconnected machine must be a function of the speed to ensure a sensible use of theintelligent current limits. The total time of the power reduction as a result of an increasedmotor or heat sink temperature contains not only the cooling time, but alsothe additionally defined Limitation Time 575.The definition of the power limit should be selected as small as possible in order togive the drive sufficient time to cool down. The reference value is the nominal powerof the frequency inverter or the set rated power of the motor.ParameterSettingsNo. Description Min. Max. Fact. sett.574 Power Limit 40.00 % 95.00 % 80.00 %575 Limitation Time 5 min 300 min 15 minIn the operation modes with overload reserve (Ixt) there is a reduction of the outputcurrent when the threshold value is exceeded, with a distinction being made betweenlong and short-term overload reserve. After the short-term overload (1s) has beenused up, the output current is reduced to the long-term overload current matching thepresent switching frequency. After the long-term overload current has been used up(60s), the output current is reduced to the rated current which also depends on theswitching frequency. If the output current has already been reduced due to the factthat the long-term overload has used up, the short-term overload is no longer availableeven if it has not been used up beforehand. The defined overload reserve (Ixt) ofthe frequency inverter is available again after a power reduction lasting 10 minutes.144 02/06