Basic Volts/Hertz - Allen-Bradley Kinetix 5700 User Manual

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.
Table 185 - Basic Volts/Hertz Definitions
Curve Feature
Start boost
Run boost
Break voltage/frequency
Motor nameplate voltage/
frequency
Maximum voltage/frequency
Figure 209 - Basic Volts/Hertz Method
Voltage, max
Base Voltage
(nameplate)
Break Voltage
Start/Accel Boost
Run Boost
Rockwell Automation Publication 2198-UM002G-EN-P - February 2019
Motor Control Feature Support
Definition
Used to create additional torque for breakaway from zero speed and acceleration
of heavy loads at lower speeds.
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.
Used to increase the slope of the lower portion of the Volts/Hertz curve, providing
additional torque.
Sets the upper portion of the curve to match the motor design. Marks the
beginning of the constant power region.
Slopes the portion of the curve that is used above base speed.
Base Frequency,
Break
Frequency (nameplate)
Appendix E
Frequency,
max
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