Motor Control Features; Scalar Motor Control; 11.07 Autophasing - ABB ACSM1 Firmware Manual

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Motor control features

Scalar motor control

It is possible to select scalar control as the motor control method instead of Direct
Torque Control (DTC). In scalar control mode, the drive is controlled with a frequency
reference. However, the outstanding performance of DTC is not achieved in scalar
control.
It is recommended to activate the scalar motor control mode in the following
situations:
• In multimotor drives: 1) if the load is not equally shared between the motors, 2) if
the motors are of different sizes, or 3) if the motors are going to be changed after
motor identification (ID run)
• If the nominal current of the motor is less than 1/6 of the nominal output current of
the drive
• If the drive is used without a motor connected (for example, for test purposes)
• If the drive runs a medium-voltage motor through a step-up transformer.
In scalar control, some standard features are not available.
IR compensation for a scalar controlled drive
IR compensation is active only when the motor
control mode is scalar. When IR compensation
is activated, the drive gives an extra voltage
boost to the motor at low speeds. IR
compensation is useful in applications that
require a high break-away torque.
In direct torque control (DTC) mode, IR
compensation is automatic and manual
adjustment is not needed.
Autophasing
Autophasing is an automatic measurement routine to determine the angular position
of the magnetic flux of a permanent magnet synchronous motor. The motor control
requires the absolute position of the rotor flux in order to control motor torque
accurately.
Autophasing is applicable to permanent magnet synchronous motors in these cases:
1. One-time measurement of the rotor and encoder position difference when an
absolute encoder or resolver (one pole pair) is used
2. With open-loop motor control, repetitive measurement of the rotor position at
every start.
Several autophasing modes are available (see parameter
MODE).
The turning mode is recommended especially with case 1 as it is the most robust
and accurate method. In turning mode, the motor shaft is turned back and forward
Drive control and features
Motor voltage
IR Compensation
No compensation

11.07 AUTOPHASING

f (Hz)