BY12512d_e.doc / Mai-08
Page 52 / 52
Hint:
Most of the inverter drives would have an analogue dead zone near zero.
This means they would not start to move with small voltage, but only break
off when we overpass a certain minimum threshold (e.g. 100 mV)
”dead zone”
100mV
Speed reference
(volts)
Analogue signal
Speed (RPM)
It is easy to understand that this kind of behavior makes it difficult to have accurate control
over the full speed range. For better performance we should therefore set an analogue offset of
100 mV (example), which, in standstill, keeps the drive already close to the break-off threshold
and makes it move immediately with a small change of the analogue signal.
To do this, you can use register “Offset Correction” (C47). Every increment there corresponds to
a voltage of 5 mV. Please note you must set the register to negative values to get positive
voltage! Example: setting to -20 will result in a +100 mV output instead of zero.
Recommended procedure: (must be done before you run the Adjust menu to set the Gains)
•
Make sure the master is in standstill. Click “Reset” to ON state, so our differential
counter is held to zero. Enable the Slave drive by an external signal (both BY125
direction outputs will be OFF at this time).
•
Change register “Offset Correction” to values like -10, -11, -12 etc. until you observe
that the drive breaks off to move. Then reduce the setting by one digit and store the
new setting.
