ABB REF545KC133AAAA Feeder terminal

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 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 (motor 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.

Autophasing is an automatic measurement routine to determine the angular position

of the magnetic flux of a permanent magnet synchronous motor or the magnetic axis

of a synchronous reluctance motor. The motor control requires the absolute position

of the rotor flux to control the motor torque accurately.

Sensors like absolute encoders and resolvers indicate the rotor position at all times

after the offset between the zero angle of rotor and that of the sensor has been

established. On the other hand, a standard pulse encoder determines the rotor

position when it rotates but the initial position is not known. However, a pulse

encoder can be used as an absolute encoder if it is equipped with Hall sensors,

albeit with coarse initial position accuracy. The Hall sensors generate so-called

commutation pulses that change their state six times during one revolution, so it is

only known within which 60° sector of a complete revolution the initial position is.