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VFD Auto-tuning and Carrier Frequency parameters

In the VFD (variable frequency drive) there are parameters called "Carrier Frequency" and "Auto-tuning", what is the effect of these parameters on improving the output waveform?

The auto-tuning function gives the VFD's vector control algorithm better than stock parameters to control the motor flux, and ultimately the output torque performance of the machine.

The carrier frequency is what the base pwm signal runs at. Typically the higher the carrier, the quieter the motor will run, but at the possible expense of damaging the windings or bearings if there is a lot of cable length, or capacitance in the output circuit. If you have an old motor, or are running a significant length of output cable, select a lower carrier frequency VFD. Now, if your instance has only a couple feet away from the variable frequency drive, you can pretty much select anything you want and not have to worry about it. For experimentation purposes you can select the different frequencies and notice the audible difference in the motor, and if you have a scope with sufficient voltage isolation probes, you can view the VFD output voltage and current waveforms. Low is sometimes around 8kHz, and high is about 15kHz for 230/480V VFDs. There is also usually another parameter for the carrier frequency as well, that either leaves the frequency constant, or allows the frequency to change as the output frequency varies. That's pretty old school, most machines today just use a fixed frequency.

In case of regenerative energy, 2 VFDs + 2 Induction Machines of same rating would be the best choice.. One VFD will power the test Machine (which acts as motor) and other VFD regenerate power from load Machine (Which acts as Generator). There are lot other loading techniques are also available which depends on application and customer requirements.

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