42 Program featuresIR compensation for scalar motor controlIR compensation (also known asvoltage boost) is available only whenthe motor control mode is scalar. WhenIR compensation is activated, the drivegives an extra voltage boost to themotor at low speeds. IR compensationis useful in applications, such aspositive displacement pumps, thatrequire a high break-away torque.Note: IR compensation is not possibleor required in vector control. Thecompensation is applied automatically.Settings• Parameters 97.13 IR compensation (page 171)• Main menu → Motor data or Main menu → Complete parameter list→ Parameter 99.04.• Parameter group 28 Frequency reference chain (page 101). Vector controlVector control is the motor control mode intended for applications where high controlaccuracy is needed. It requires an identification run at startup. Vector control cannotbe used in all applications, e.g. sine filters.Vector control is based on stator flux and motor torque values.• Stator flux is calculated by integrating the motor voltage in vector space.The estimate of stator flux can be improved by utilizing the identified motor model.• Motor torque is calculated as a cross product of the stator flux and the rotorcurrent.Both values can be achieved by controlling the output semiconductors switching. Theoutput frequency is changed only when the actual values of stator flux and motortorque are different from their reference values by more than the allowed hysteresis.The reference value for the torque controller comes from the speed controller ordirectly from an external torque reference source.Notes:• Actual motor shaft speed is not needed for motor control.• Vector control also requires measurement of the DC voltage and two motor phasecurrents.The difference of vector control from the traditional control are:Motor voltagef (Hz)IR compensationNo compensation
