Emerson PACMotion VFD Series User Manual page 64

Synchronous Motors
Overview
PACMotion VFD provides open loop vector control of the following synchronous motor types.
Permanent Magnet AC (PM AC) Motors and Brushless DC (BLDC) Motors
PACMotion VFD can be used to control Permanent Magnet AC or Brushless DC motors without a feedback
encoder or resolver. These motors operate synchronously, and a vector control strategy is used to maintain
correct operation. In general, the motor can be operated between 10% - 100% of rated speed with a correctly
selected and configured drive. Optimum control is achieved when the motor back EMF / Rated speed ratio is
>= 1 V/Hz. Motors with Back EMF / Rated frequency ratio below this level may not operate correctly, or may
operate only with reduced speed range.
PM AC and BLDC motor control employs the same strategy, and the same commissioning method is applied.
WARNING
Permanent Magnet motors (including BLDC) produce an output voltage known as the Back EMF when the
shaft is rotated. The user must ensure that the motor shaft cannot rotate at a speed where this Back EMF
exceeds the voltage limit for the drive, otherwise damage can occur.
The following parameter settings are necessary before attempting to operate the motor.
• Ensure advanced parameter access is enabled by setting P1-14 = 101 (default value for security access).
• Enter the motor nameplate details into the relevant parameters as follows:
o P1-07 Back EMF at Rated Frequency / Speed (kE)
This is the voltage imposed by the magnets at the drive output terminals when the motor operates at
rated frequency or speed. Some motors may provide a value for volts per thousand RPM, and it may
be necessary to calculate the correct value for P1-07.
o P1-08 Motor Rated Current
o P1-09 Motor Rated Frequency
o (Optional) P1-10 Motor Rated Speed (Rpm).
• Select PM Motor Speed control mode by setting P4-01 = 3 or BLDC Motor Speed Control by setting P4-01 = 5.
• Ensure that the motor is correctly connected to the drive.
• Carry out a motor data Autotune by setting P4-02 = 1.
o The autotune measures the electrical data required from the motor to ensure good control.
• To improve motor starting and low speed operation, the following parameters may require adjustment:
o P7-14: Low Frequency Torque Boost Current: Injects additional current into the motor to help rotor
alignment at low output frequency. Set as % of P1-08.
o P7-15: Low Frequency Torque Boost Frequency Limit: Defines the frequency range where the torque
boost is applied. Set as % of P1-09.
Following the steps above, it should be possible to operate the motor. Further parameter settings are possible
to enhance the performance if required, please refer to your Emerson Sales Partner for more information.
64 PACMotion VFD AC Variable Speed Drive User Guide GFK-3111A