Toshiba VF-S11 Drive Problem

Have you tried the following first?

Read the manual.

Ask Toshiba for support.

One of the possibilities is that the load presents so much torque at low speed that the drive trips on overcurrent.

If the settings are correct, then the drive is doing its job.

See #1↑.

Gearbox.

Hand crank.

That drive is capable of Sensorless Vector Control (or so it says). Vector control allows a drive to extend the speed range from 4:1 (as it is in standard V/Hz mode), to better than 50:1. That means that in a 50Hz motor design, you can only get speed and torque accuracy down to about 15Hz with V/Hz mode and if you use Vector control, you can get it down to 1Hz. It may be that the load is such that although the VFD is telling the motor to run at 10Hz, in V/Hz mode the drag from the load is only allowing it to turn at 7Hz, so you now have 30% slip and the motor will pull more current and overload. With Vector Control, the drive will tell the motor to run at 10Hz and then observe it, if it does not, then it boosts the torque vector to maintain the accuracy.

Check parameter AU2, if the value is 0, 1 or 3 then it is in V/Hz operation. It must be a value of 2 if you want Vector operation. Then read the instructions about setting up the Auto-Tuning for Vector Control. If it is in Vector Control, then did you perform the Autotune at set up? If not, it might as well not be in Vector mode. If you did both, it just may be that the nature of your load profile is such that a cheap little drive like this is incapable of being accurate enough to do what you are demanding of it and you need a better drive.

By the way, if you plan on running it at 10Hz for anything more than about a 10% duty cycle (i.e. 1 minute at 10Hz followed by 10 minutes at full speed), you had better add fan forced cooling to that motor. The built-in cooling fans (if any) stop working at low speeds too.