HowTo: How to get Maximum Torque at Low Speed from a Simple VxF Inverter

A simple VxF Inverter will perform well at low speed when the ‘Boost’ parameter is set correctly. The method of setting this is as follows:-

1. Remove the final drive to the machine, so the motor is completely free of load.
2. Run the Inverter at 50Hz.
3. Find the motor current in the drive diagnostic and make a note of it.
4. Run the inverter at 5Hz.
5. Adjust the Boost parameter until the drive diagnostic of current shows the same value you noted for 50Hz.
6. Save the parameter, if this is a function of the drive.

The motor will be correctly fluxed and give maximum torque down to very low speed. Typically 5Hz or less. If the Inverter has ‘Auto-boost’ to be set manually as a value. Take 50% of the value above and load it into ‘Manual- Boost’ and enter 50% into ‘Auto-boost’. This will make maximum torque when the motor and drive sees maximum load at low speed.