Rockwell Automation Liqui-Flo DBT Reach Drive - Manual (Page 216)

Appendix D-2 DBT Reach Drive User Manual
This technology is good for basic centrifugal fan/pump operation and for most
multi-motor applications. Torque production is generally good.
Sensorless Vector
This technology combines the basic Volts/Hertz concept with known motor parameters
such as Rated FLA, HP, Voltage, stator resistance and flux producing current.
Knowledge of the individual motor attached to the drive allows the drive to adjust the
output pattern to the motor and load conditions. By identifying motor parameters, the
drive can maximize the torque produced in the motor and extend the speed range at
which that torque can be produced.
This technology is excellent for applications that require a wider speed range and
applications that need maximum possible torque for breakaway, acceleration or
overload. Centrifuges, extruders, conveyors and others are candidates.
Torque Controllers
Vector
This technology differs from the two above, because it actually controls or regulates
torque. Rather than allowing the motor and load to actually determine the amount of
torque produced, Vector technology allows the drive to regulate the torque to a defined
value. By independently identifying and controlling both flux and torque currents in the
motor, true control of torque is achieved. High bandwidth current regulators remain
active with or without encoder feedback to produce outstanding results.
This technology is excellent for those applications where torque control, rather than
mere torque production, is key to the success of the process. These include web
handling, demanding extruders and lifting applications such as hoists or material
handling.
Vector Control can operate in one of two configurations:
1. Encoderless
Not to be confused with Sensorless Vector above, Encoderless Vector y means that a
feedback device is not required. Torque control can be achieved across a significant
speed range without feedback.
2. Closed Loop (with Encoder)
This industry leading technology allows the drive to control torque over the entire
speed range, including zero speed. For those applications that require smooth torque
regulation at very low speeds or full torque at zero speed, Closed Loop Vector Control
is the answer.
Speed Regulators
The Reach Drives, regardless of their motor control technology (Volts/Hz, Sensorless
Vector or Vector) can be set up to regulate speed. Speed regulation and torque
regulation must be separated to understand drive operation.
The Reach Drive can offer improved speed regulation by adding speed feedback.
Using a speed feedback device (encoder) tightens speed regulation to 0.001% of
base speed and extends the speed range to zero speed.