APPENDIX D (Continued)
b) Flux vector drives use a method of controlling
torque similar to that of DC drive systems, including wide speed
control range with quick response. Flux vector drives have the
same power section as PWM drives, but use a sophisticated closed
motor's rotor position and speed is monitored in real time via a
resolver or digital encoder to determine and control the motor's
actual speed, torque, and power produced.
c) By controlling the inverter section in response to
actual load conditions at the motor in a real time mode, superior
torque control can be obtained. The personality of the motor
must be programmed into or learned by the drive in order for it
to run the vector control algorithms. In most cases, special
motors are required due to the torque demands expected of the
The following are advantages of this new drive
Quick response to changes in load, speed, and
Ability to provide 100 percent rated torque at
(4) Lower maintenance cost as compared to DC
motors and drives.
The following are disadvantages:
Higher initial cost as compared to standard
Requires special motor in most cases.
Drive setup parameters are complex.
While flux vector technology offers superior performance for
certain special applications, it would be considered "overkill"
for most applications well served by standard PWM drives.
Application of VFD's to Specific Loads. VFD's are the
most effective energy savers in pump and fan applications, and