Rockwell Automation 20A PowerFlex 70EC/700VC - Manual (Page 103)

Speed Reference 99
Network Reference
When a network (communication adapter) is selected as the speed reference, a 16
bit word is used as the speed reference. If [Direction Mode], parameter 190 is set to
“Bipolar”, the most significant bit (MSB) is used for direction control. Otherwise,
the MSB is ignored. The remaining 15 bits (32767 decimal) provide the magnitude.
By default, the maximum network value is scaled to [Maximum Freq], parameter
55. Using the default value of 130 Hz results in the following scaling relationship:
Example 1:Maximum Network Reference = Maximum Frequency
− [DIP Ref Select], parameter 298 = “Max Freq”
− [Maximum Freq], parameter 55 = 130 Hz
− [Maximum Speed], parameter 82 = 60 Hz
− Speed Reference = (Network value/Maximum Freq) x 32767
When full speed (60 Hz) is desired, the following network value must be sent:
− (60/130) x 32767 = 15123
[Maximum Freq], parameter 55 cannot always simply be changed to 60 Hz so that the maximum
network value is equal to 60 Hz. An internal control rule between Maximum Frequency, Overspeed
Limit, and Maximum Speed usually prevents such a change. However, [DPI Ref Select], parameter 298
allows a setting which changes the scaling to Maximum Speed instead of Maximum Frequency, as
shown in the following example:
Example 2: Maximum Network Reference = Maximum Speed
− [DIP Ref Select], parameter 298 = “Max Speed”
− [Maximum Freq], parameter 55 = 130 Hz
− [Maximum Speed], parameter 82 = 60 Hz
Speed Reference = (Network value/Maximum Speed) x 32767
When full speed (60 Hz) is desired, the following network value must be sent:
(60/60) x 32767 = 32767
Jog
When the drive is not running, pressing the HIM Jog button or a programmed Jog
digital input will cause the drive to jog at a separately programmed jog reference.
This speed reference value is entered in [Jog Speed], parameter 100.
Scaling of an Analog Speed Reference
Refer to "Analog Inputs" on page 4 .
Polarity
The reference can be selected as either unipolar or bipolar. Unipolar is limited to
positive values and supplies only the speed reference. Bipolar supplies both the
speed reference AND the direction command: + signals = forward direction and –
signals = reverse direction.
Trim
If the speed reference is coming from the source specified in [Speed Ref A Sel] or
[Speed Ref B Sel], it can be trimmed by variable amount.