Allen-Bradley PowerFlex 70 Enhanced Control, Справочное руководство, Страница: 12 / 170

8 Analog Inputs
Square Root
The square root function can be applied to each analog input through the use of
[Analog In Sq Root]. The function should be enabled if the input signal varies with
the square of the quantity (e.g. drive speed) being controlled.
If the mode of the input is bipolar voltage (–10v to 10v), then the square root
function will return 0 for all negative voltages.
The function uses the square root of the analog value as compared to its full scale
(e.g.
) and multiplies it times the full scale of what
it will control (e.g. 60 Hz).
The complete function can be describes as:
Setting high and low values to 0V, 10V, 0 Hz and 60 Hz, the expression reduces to:
Signal Loss
Signal loss detection can be enabled for each analog input. The [Analog In x Loss]
parameters control whether signal loss detection is enabled for each input and
defines what action the drive will take when loss of any analog input signal occurs.
One of the selections for reaction to signal loss is a drive fault, which will stop the
drive. All other choices make it possible for the input signal to return to a usable
level while the drive is still running.
•
Hold input
•
Set input Lo
•
Set input Hi
•
Goto Preset 1
•
Hold Output Frequency
5V 0.5 or 50% and 0.5 0.707 = =
Analog Value - [Analog In x Lo]
[Analog In x Hi] - [Analog In x Lo]
------------------------------------------------------------------------
⎝ ⎠
⎛ ⎞
(
Speed Ref A Hi
[ ]
– [Speed Ref A Lo]
)
[Speed Ref A Lo] +
×
Analog Value
10V
-----------------------------
⎝ ⎠
⎛ ⎞
60 Hz
×
2
4
6
8
10
2 0 4 6
Input (Volts)
Output (Volts)
8 10