Unidrive M702 / HS72 Control Getting Started Guide 7
Issue Number: 2
Safety information
Introduction
Control connections Getting started
Basic parameters
(Menu 0)
Running the motor Further information
Quadratic V/F mode
The voltage applied to the motor is directly proportional to the square of the frequency except at low
speed where a voltage boost is provided which is set by the user. This mode can be used for running
fan or pump applications with quadratic load characteristics or for multi-motor applications. This
mode is not suitable for applications requiring a high starting torque.
2.1.2 RFC-A mode
Rotor Flux Control for Asynchronous (induction) motors (RFC-A) encompasses closed loop vector
control with a position feedback device
With position feedback
For use with induction motors with a feedback device installed. The drive directly controls the speed
of the motor using the feedback device to ensure the rotor speed exactly as demanded. Motor flux is
accurately controlled at all times to provide full torque all the way down to zero speed.
Without position feedback (Sensorless)
Sensorless mode provides closed loop control without the need for position feedback by using
current, voltages and key motor parameters to estimate the motor speed. It can eliminate instability
traditionally associated with open loop control such as operating large motors with light loads at low
frequencies.
2.1.3 RFC- S
Rotor Flux Control for Synchronous (permanent magnet brushless) motors (RFC-S) provides closed
loop control with position feedback device.
With position feedback
For use with permanent magnet brushless motors with a feedback device installed.
The drive directly controls the speed of the motor using the feedback device to ensure the rotor
speed is exactly as demanded. Flux control is not required because the motor is self excited by the
permanent magnets which form part of the rotor.
Absolute position information is required from the feedback device to ensure the output voltage is
accurately matched to the back EMF of the motor. Full torque is available all the way down to zero
speed.
Without position feedback
For use with permanent magnet brushless motors without a feedback device installed.
Flux control is not required because the motor is self excited by the permanent magnets which form
part of the rotor.
Full torque is available all the way down to zero speed, with salient motors.
Unidrive M702_HS72 Control GSG Iss2.book Page 7 Friday, December 12, 2014 1:05 PM
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