Rockwell Automation Publication 2198-UM002L-EN-P - October 2021 399
Appendix F Motor Control Feature Support
Basic Volts/Hertz
Volts/hertz operation creates a fixed relationship between output voltage and
output frequency. Voltage is applied to the motor, which is based on the
operating frequency command at a fixed volts/hertz ratio. The ratio is
calculated from the motor nameplate data and entered into the Logix Designer
application>Axis Properties>Frequency Control category.
The Basic Volts/Hertz method provides various patterns. The default
configuration is a straight line from zero to rated voltage and frequency. As
seen in Figure 209
, you can change the volts/hertz ratio to provide increased
torque performance when required by programming five distinct points on
the curve.
Figure 209 - Basic Volts/Hertz Method
Table 198 - Basic Volts/Hertz Definitions
Curve Feature Definition
Start boost
Used to create additional torque for breakaway from zero speed and
acceleration of heavy loads at lower speeds.
Run boost
Used to create additional running torque at low speeds. The value is typically
less than the required acceleration torque. The drive lowers the boost voltage to
this level when running at low speeds (not accelerating). This reduces excess
motor heating that could result if the higher start/accel boost level were used.
Break voltage/frequency
Used to increase the slope of the lower portion of the Volts/Hertz curve,
providing additional torque.
Motor nameplate voltage/
frequency
Sets the upper portion of the curve to match the motor design. Marks the
beginning of the constant power region.
Maximum voltage/frequency Slopes the portion of the curve that is used above base speed.
Frequency,
max
Base Frequency,
(nameplate)
Break Voltage
Start/Accel Boost
Run Boost
Base Voltage
(nameplate)
Voltage, max
Break
Frequency
To Next Page
Loading...
Need help?
General
