Rockwell Automation GV3000/SE AC Gen. Purpose and Vector Drive Software Start-Up and Ref. Manual - Manual (Page 219)

Drive Regulation Overview H-1
A
PPENDIX
H
Drive Regulation Overview
The GV3000/SE digital drive provides vector or volts/hertz regulation of AC motors.
Parameter P.048 (Volts/Hertz or Vector Regulation) is used to select the type of
regulation for the application.
Volts/Hertz Regulation (P.048 = U-H)
Volts/hertz regulation provides general-purpose open-loop AC drive control. It does
not use an encoder feedback device. In this type of control, the regulator maintains a
programmed ratio of voltage to an output frequency, which provides constant or
variable motor torque across a wide speed range. An internal function generator
calculates the output motor voltage based on requested frequency and user-specified
motor characteristics. The control loop output switches the power device gates,
generating a pulse-width-modulated (PWM) waveform to the motor.
Figure H.1 shows a block diagram of the V/Hz regulator.
Vector Regulation (P.048 = UEC)
Vector regulation allows dynamic open- or closed-loop performance in an AC drive
similar to that achieved with a DC drive. Torque is constant across the motor’s base
speed range in both forward and reverse directions. The drive uses two digital control
loops, speed and torque, to obtain vector performance. An outer control loop is also
available. The speed loop executes every 5 ms. The outer control loop executes every
20 ms.
The speed loop reference can be an internal or an external source. For flux vector
control (FVC), speed loop feedback is provided by an encoder attached to the motor’s
shaft. For sensorless vector control (SVC), speed feedback is estimated based on
motor parameters. The speed loop provides inertia compensation, losses
compensation, and current compounding.
The torque will vary to maintain the motor at the requested speed. The torque control
loop output controls the switching on and off of the power devices, generating a
pulse-width-modulated (PWM) waveform to the motor.
Figure H.2 shows a block diagram of the flux vector regulator. Figure H.3 shows a
block diagram of the sensorless vector regulator. Figures H.4 and H.5 show detail of
the reference and speed loop portions of the vector regulator.
The optional outer control loop (OCL) acts as a trim to the speed loop reference
signal. Figure H.7 shows a block diagram of the outer control loop portion of the vector
regulator.
If a network board is installed, the OCL reference comes from the network trim
reference register based on P.064 (Option Port: Network Trim Reference Source) as
defined for each network type. (Refer to the specific network board instruction manual
for more information on P.064.)