Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 17)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 17
Drive Configuration Chapter 1
Adjustable Voltage As standard AC drive applications are expanding into new markets, new control
methods are required to meet these market demands for electromagnetic
applications. Some of these applications, listed below, use non-motor or non-
standard motors that require independent control of load frequency and voltage.
• Vibration welding
• Induction heating
• Power supplies
• Vibratory feeders or conveyors
• Electromagnetic stirring
• Resistive loads
Standard inverter control modes consist of volts per hertz (V/Hz), with boost
selections, speed feedback selection, fan, pump, and economize, flux vector (FV),
with encoder and encoder less modes. The control of the output voltage/
frequency relationship of the variable frequency inverter must be maintained in
the linear and nonlinear (over-modulation) regions. Voltage linearity is achieved
by maintaining a constant voltage/frequency ratio over the entire operating
region. The variable frequency inverter must deliver an adjustable-frequency
alternating voltage whose magnitude is related to the output frequency. As the
linear-to-nonlinear transition begins, the control must compensate for the lost
voltage and deliver a linear output voltage profile.
In adjustable voltage control mode, the output voltage is controlled
independently from the output frequency. The voltage and frequency
components have independent references and acceleration/deceleration rates.
The adjustable voltage control mode operation enables separate control of the
output voltage and the output frequency for use on applications that are typically
non-motor types. The voltage and frequency components have independent
references and independent acceleration and deceleration rates. Both the voltage
and frequency can be set to any point within their respective range. The
following graph illustrates these functional ranges.
0
0
Rated Voltage
Voltage
Frequency Max Frequency