Smooth starting is a positive aspect in the operation of motors with variable frequency drives. For most applications and certainly for centrifugal loads, starting currents are very low, acceleration is smooth and controlled, Gates AX44 and because of low slip, rotor heating will be greatly reduced. The lower the voltage and the frequency of the stator, the more significant the voltage drop will be, so that at low frequencies, maintaining the ratio between the frequency and the voltage, the flow and consequently the machine torque will greatly reduce.
Typical drive installations are configured to restrict the motor current to 100% of the nominal, thus ending the starter stresses in the motor insulation and in the mains. Most applications are designed to keep the V / Hz ratio constant, keeping the electromagnetic flow in the engine air gap constant, so at low frequencies the voltage will be low. During startup the drive controls the voltage and frequency to allow the motor to operate close to the nominal slip and flow and is operating on the stable portion of the Torque x r.p.m.