Use this Speed Search function with induction motors. Set b3-24 = 2 [Speed Search Method Selection = Current Detection 2]. Current Detection Speed Search injects current into the motor to detect the speed of an induction motor. Speed Search increases the output voltage for the time set in L2-04 [Powerloss V/f Recovery Ramp Time], starting from the maximum output frequency or the frequency reference.
Figure 1. Current Detection 2 after Momentary Power Loss
Note:
After you restore power, the drive will not do Speed Search until the time set in b3-05 [Speed Search Delay Time] expires. This means that the drive will not always start Speed Search when the time set in L2-03 [Minimum Baseblock Time] expires.
If you enter the Run command at the same time as Speed Search, the drive will not do Speed Search until the time set in L2-03 expires. When the value set in L2-03 < b3-05, the drive will use the wait time set in b3-05.
Figure 2. Speed Search Selection at Start (Current Detection Type)
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Sudden Movement Hazard
Do not do Current Detection Speed Search with light loads or a stopped motor.
If you do Auto-Tuning in these conditions, the motor can suddenly accelerate and cause serious injury or death.
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Note:
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You cannot use Current Detection Speed Search with PM motors.
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If the drive detects oL1 [Motor Overload] during Current Detection Speed Search, decrease b3-03.
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If the drive detects oC [Overcurrent] or ov [Overvoltage] during Current Detection Speed Search after the drive recovers from a momentary power loss, increase L2-03.
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If b3-01 = 1 [Speed Search at Start Selection = Enabled], too much current will flow when the motor starts. If there is too much current at start, it will decrease the service life of the drive IGBTs over time.