FR-A701 INSTRUCTION MANUAL (Applied) - Automation Systems ...

Speed control by real sensorless vectorcontrol, vector control4.4.7 Prevent the motor from overrunning (Pr. 285, Pr. 853, Pr. 873)VectorThis function prevents the motor from overrunning when the load torque is too large and incorrect number ofencoder is set.ParameterNumberName Initial Value Setting Range Description285Speed deviation excess9999 Without speed deviation excessive9999detection frequency *10 to 30Hz If the difference (absolute value) between the853 *2 Speed deviation time 1.0s 0 to 100sspeed command value and actual speed duringspeed control under vector control exceeds thePr. 285 Speed deviation excess detection frequencyfor more than the time set in Pr. 853 Speeddeviation time, speed deviation excessive occursand inverter fault (E. OSD) appears, resulting ina trip.873 *2 Speed limit 20Hz 0 to 120Hz Frequency is limited at the set frequency + Pr. 873.*1 Acts as overspeed detection frequency under encoder feed back operation. (Refer to page 192)*2 This parameter can be set when the FR-A7AP (option) is mounted.(1) Speed deviation excessive (Pr. 285, Pr. 853)When the deviation between the set frequency and actual speed is large, e.g. too large load torque, this function cancause the inverter to provide a speed deviation excessive fault (E.OSD) and come to a trip.Frequency(Hz)Fault output(across A-C)Pr. 853OFFPr. 285Set frequencyActual speedONSpeed deviationexcessive fault activated(E. OSD)Time(2) Speed limit (Pr. 873)This function prevents the motor from overrunning when the setting of number of encoder pulses and the actualnumber differ.When the setting of number of encoder pulses is smaller than the actual number, the motor may increase its speed.To prevent this, restrict the output frequency with frequency (obtained by adding the set frequency and Pr. 873 ).Set speed + Pr. 873 valueValue of Pr. 873Actual speedat error occurrenceSet speedSpeed duringnormal operation.⋅⋅CAUTIONIf automatic restart after instantaneous power failure (Pr. 57 ≠ 9999) is selected when the setting of number of encoder pulses issmaller than the actual number, the output speed is limited with the synchronous speed obtained by adding the maximumsetting (Pr. 1) and Pr. 873 setting.When speed limit function is activated due to regenerative torque limit, output torque may suddenly decrease. In addition,output phase loss (E.LF) may occur when speed limit function is activated during pre-excitation.When the setting of number of encoder pulses are correct, it is recommended to set a mamimum value (120Hz) in Pr. 873.Reference parametersPr. 285 Overspeed detection frequency Refer to page 192.100