Rockwell Automation Publication 20D-PM001D-EN-P - March 2019 163
Application Notes Appendix B
Permanent Magnet Control
Permanent magnet control is used with permanent magnet motors. Permanent
magnet motor control is selected by setting parameter 485 [Motor Ctrl Mode] =
2 “Pmag Motor”.
• Permanent magnet motor control requires either a Hi-Resolution
Stegmann encoder or compatible resolver feedback on the motor.
• Motor data and an autotune is required for correct operation in this mode.
Refer to PowerFlex 700S Permanent Magnet Motor Specifications
on page
199
for a list of compatible Allen-Bradley® permanent magnet motors and
motor data to be used with the PowerFlex 700S Phase II drives.
Volts/Hertz Control - v2.003 and Later
Volts/Hertz control is used in fan, pump, or multi-motor applications. Volts/
Hertz operation creates a fixed relationship between output voltage and output
frequency.
Configuration:
Volts/Hertz control is selected by setting parameter 485 [Motor Ctrl Mode] = 3
“V/Hz”.
Volts/Hertz allows a wide variety of patterns using linear segments. The default
configuration is a straight line from zero to rated voltage and frequency. This is
the same volts/hertz ratio that the motor would see if it were started across the
line. As seen in the diagram below, the volts/hertz ratio can be changed to
provide increased torque performance when required. The shaping takes place by
programming five distinct points on the curve:
1. Parameter 527 [Start/Acc Boost] is used to create additional torque for
breakaway from zero speed and acceleration of heavy loads at lower speeds.
2. Parameter 528 [Run Boost] is used to create additional running torque at
low speeds. The value is typically less than the required acceleration
torque. The drive will lower the boost voltage to this level when running at
low speeds (not accelerating). This reduces excess motor heating that
could be caused if the higher start/accel boost level were used.
3. Parameters 529 [Break Voltage] and 530 [Break Frequency] are used to
increase the slope of the lower portion of the Volts/Hertz curve, providing
additional torque.
4. Parameters 1 [Motor NP Volts] and 3 [Motor NP Hertz] set the upper
portion of the curve to match the motor design and mark the beginning of
the constant horsepower region.
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