AC powersupplyOutputfrequencyOutputcurrentOFFONOutput frequency beforemomentary power lossSelectedfrequencyreferenceMin. Baseblock Time (L2-03)Decel timeset to b3-03 Waits for twiceas long as L2-04Speed Search operationcurrent set to b3-02b3-05Figure 1.15 Current Detection Speed Search after Power LossNote: After power is restored, the drive waits until the time set to b3-05 has passed before performing Speed Search. Thereby the Speed Searchmay start not at the end of L2-03 but even later.When Speed Search is applied automatically with the Run command, the drive waits for the minimum baseblock time set toL2-03 before starting Speed Search. If L2-03 is lower than the time set to parameter b3-05, then b3-05 is used as the wait time.Run commandOutputfrequencyOutput currentOFF ONb3-02(Speed searchoperationcurrent)Decel time setset to b3-03Waits for twiceas long as L2-04SelectedfrequencyreferenceMinimum Baseblock Time (L2-03)Max. output frequencyor the specifiedfrequency referenceFigure 1.16 Current Detection Speed Search at Start or Speed Search Command by Digital InputNotes on Using Current Detection Type Speed Search• Shorten the Speed Search deceleration time set to b3-03 if an oL1 fault occurs while performing Current Detection SpeedSearch.• Current Detection Speed Search is not available when using OLV Control for PM motors.• Increase the minimum baseblock time set to L2-03 if an overcurrent or overvoltage fault occurs when performing SpeedSearch after power is restored following a momentary power loss.n Speed Estimation Type Speed Search (b3-24 = 1)This method can be used for a single induction motor connected to a drive. Do not use this method if the motor is one or moreframe size smaller than the drive, at motor speeds above 200 Hz, or when using a single drive to operate more than one motor.Speed Estimation is executed in the two steps described below:Step 1: Back EMF Voltage EstimationThis method is used by Speed Search after baseblock (e.g., a power loss where the drive CPU continued to run and the Runcommand was kept active). Here, the drive estimates the motor speed by analyzing the back EMF voltage and outputs theestimated frequency and increases the voltage using the time constant set in parameter L2-04. After that, the motor is acceleratedor decelerated to the frequency reference starting from the detected speed. If there is not enough residual voltage in the motorwindings to perform the calculations described above, the drive will automatically proceed to step 2.1.2 b: Application28 YASKAWA ELECTRIC SIEP YEAHHP 01B YASKAWA AC Drive – A1000 HHP Programming Manual
