On a loaded conveyor, the inverter should be set to a control mode and ramp that give enough starting torque. A loaded belt must first overcome friction and the inertia of the material; the starting torque required can be noticeably higher than the running torque. In direct-on-line starting the motor produces this torque by drawing a high current from the mains; with an inverter, starting current is limited by the inverter's overload limit.

Settings to watch:

  • Control mode: Sensorless vector control gives higher torque at low speed than V/f mode. The motor nameplate data should be entered correctly in the inverter and motor identification (autotune) carried out.
  • Torque boost: Raises the voltage somewhat at low frequency in V/f mode; too much heats the motor.
  • Acceleration ramp: Choose a time in which belt and material accelerate without slipping. Too short a ramp trips the inverter on overcurrent.
  • Deceleration: On a loaded, inclined belt the motor acts as a generator while slowing down; a braking resistor or a longer ramp is needed.
  • Overload class: The inverter should be selected for heavy duty.

If only a soft start is needed and no speed adjustment, the difference from a soft starter is explained in the motor connection and starting questions guide. For motors suitable for conveyors, see the conveyor belt electric motors page.