Drive control and features38Motor control featuresScalar motor controlIt is possible to select scalar control as the motor control method instead of DirectTorque Control (DTC). In scalar control mode, the drive is controlled with a frequencyreference. However, the performance of DTC is not achieved in scalar control.It is recommended to activate the scalar motor control mode in the followingsituations:• In multimotor drives: 1) if the load is not equally shared between the motors, 2) ifthe motors are of different sizes, or 3) if the motors are going to be changed aftermotor identification (motor ID run)• If the nominal current of the motor is less than 1/6 of the nominal output current ofthe 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 driveIR stands for voltage.I (current) × R (resistance) = U (voltage).IR compensation is active only when the motorcontrol mode is scalar. When IR compensationis activated, the drive gives an extra voltageboost to the motor at low speeds. IRcompensation is useful in applications thatrequire a high break-away torque.In direct torque control (DTC) mode, IRcompensation is automatic and manualadjustment is not needed.f (Hz)Motor voltageNo compensationIR Compensation50% of nominalfrequency
