Rockwell Automation 20B PowerFlex 700 AC Drives Vector Control (v4.001 and up) - Manual (Page 110)

110 Rockwell Automation Publication 20B-UM002G-EN-P - July 2014
Appendix C Application Notes
Enabling Adjustable Voltage
Adjustable Voltage is enabled in [Motor Cntl Sel], parameter 053 by selecting “5,
Adj Voltage.” In this mode, current limit will now reduce voltage instead of
frequency when the threshold is reached. Aggressive ramp rates on the voltage
command should be avoided to minimize nuisance overcurrent trips.
Fixed Frequency Control Applications
Many of the applications require a fixed frequency operation with variable
voltage levels. For these applications it is best to set the frequency ramp rates to
“0” using [Accel Time 1 & 2] and [Decel Time 1 & 2], parameters 140-143. The
ramp rates for output voltage are independently controlled with parameters [Adj
Volt AccTime] and [Adj Volt DecTime], parameters 675-676.
Output Filters
Several adjustable voltage applications can require the use of output filters. Any
L-C or sine wave filter used on the output side of the drive must be compatible
with the desired frequency of operation, as well as the PWM voltage waveform
developed by the inverter. The drive is capable of operating from 0-400 Hz
output frequency and the PWM frequencies range from 2-10 kHz. When a filter
is used on the output of the drive, [Drive OL Mode], parameter 150 should be
programmed so that PWM frequency is not affected by an overload condition
(i.e. “0, Disabled” or “1, Reduce CLim”).
Trim Function
The trim function can be used with the Adjustable Voltage mode. The value of
the selection in [Adj Volt TrimSel], parameter 669 is summed with the value of
[Adj Volt Select], parameter 651. Scaling of the trim function is controlled with
[Adj Volt Trim%], parameter 672. When the sign of [Adj Volt Trim%] is
negative, the value selected in [Adj Volt TrimSel] is subtracted from the reference.
Process Control
The Process PI loop in the drive can be configured to regulate the frequency or
voltage commands of the drive. Typical applications using the Adjustable Voltage
mode will close the loop around the voltage command. Process PI is enabled by
selecting “1, AdjVoltTrim” in bit 10 of [PI Configuration], parameter 124. This
bit configures the PI regulator output to trim the voltage reference, rather than
the torque or speed references. The trim can be configured to be exclusive by
selecting “1, Excl Mode” in bit 0 of [PI Configuration], parameter 124. Trimming
the voltage reference is not compatible with trimming the torque reference, thus
if bits 10 and 8 of [PI Configuration] are set, a type II alarm will occur, setting bit
19 (PI Cfg Cflct) in [Drive Alarm 2], parameter 212.