VB5N series inverter 
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For example: Fig 4-39: 
 
Fig.4-39 zero-frequency backlash 
Start process:   
After start command is sent, the motor will start and accelerate to the preset frequency in the Acc time when the setting 
frequency reaches or exceeds Fb. 
Stop process: 
The inverter will not stop immediately if the setting frequency is lower than Fb, only when the setting frequency reaches 
Fa, the inverter will stop output. 
Fa points to zero-frequency wakeup threshold (P7.18), Fb-Fa points to zero-frequency wakeup backlash (P7.19). 
This function can realize domant function and save the energy, besides, the inverter will not frequent start at threshold fre-
quency by defining the backlash width. 
4-2-9. Simple PLC operation parameters (Group P8) 
Simple PLC function is a multi-speed generator, inverter can auto-change frequency and direction according to the running 
time to satisfy the technical requirements. See Fig4-40. 
Fb: Pa+ zero-frequency backlash 
Fa: zero-frequency run threshold