Rockwell Automation GV3000/SE 230VAC 1-20 HP GP & Vector Drive Ver. 6.04 Software Start-Up and Ref. - Manual (Page 215)

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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 G.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 if an option board is installed in the drive. 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 G.2 shows a block diagram of the flux vector regulator. Figure G.3 shows a
block diagram of the sensorless vector regulator. Figures G.4 and G.5 shows 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 G.6 shows a block diagram of the outer control loop portion of the
vector regulator.
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PPENDIX
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Drive Regulation Overview