Please comments on the impact on the VFD,  using a resistor load bank for testing instead of a motor.

motor can be modeled as the series connection of resistor , inductor and back EMF. without inductor, nothing smooths out the harmonic voltage. that means the VFD will see a lot of harmonic current. without back EMF , nothing counts against the VFD voltage. that means a little voltage will creates a large current, depending on how large the resistor you will use.

Dear Sean,
Thank You for the information.

I have taught drives for many years at a university and one of my favorite demos was to take a 3 phase 230vac drive and wire the motor output leads to three 120vac light bulbs connected in a wye. If you set the drive to a slow accel rate, you can visibly watch the 3 light bulbs light up in a rotating pattern that gets brighter and faster as the Volts/Hertz increase. It is a poor way to test a drive but it is a good way to visibly demonstrate rotating 3 phase motor speed and direction control.

A motor that has the current in phase with its back EMF is actually a pure resistor with an series inductive drop. A good starting point is to choose a resistor value corresponding to the rated power output of the motor. A 110 volt, 1/2 hp motor motor would be emulated with 32.4 ohm. (373 watt) The stator resistive loss is negligible compared to this load. However, that stator inductive drop is large at the top running speed. So, for an accurate emulation, you need to add the equivalent stator inductance. A vector drive should increase the voltage and adjust its phase to assure I and V are phased together at the resistor.

There are lots of ways to test an inverter.

For a quick and dirty test, I have used a NEMA motor stator--just un-bolt the end bell and pull out the rotor. Once, when this was not practical, I went to an electric supply warehouse and brought back three spools of single-0 welding cable. We hooked them up in a wye configuration as three big air-core inductors and tested our inverter into that load.

There is some good feedback here. Note that the current in the output devices and any current regulation you plan on is dependent on the inductance of the motor. You can test with resistance but nothing will limit dv/dt much.
A used motor or motor parts or coils of wire would be better. Inductors and transformers are also good. Be a little careful of the voltage ring up at the load. It might damage the windings if they are not designed for it.
Good luck

In my experience, if you drive a purely resistive load with your inverter, your DC bus voltage will drop significantly. We have done lots of inverter life testing with simulated motor loads which consisted of power resistors and transformer coils. This worked quite well.

Hi Rick, when you mentioned inverter life test, do you mean acceleration life test (test inverter life in short time)? Could you introduce how this kind of test is designed, or any good article I can refer to? Many thanks.

Hi Sean, this was for accelerated life testing (ALT) where we test the inverter for it's intended life time in a short time period. In our case, we installed 10 or 15 inverters in a temperature/humidity chamber and drove the simulated motor loads at specific intervals 24 hours a day under various temperature/humidity points until we meet the equivalent life of the product. The goal is to identify any hardware components that are prone to failure in the field and improve the robustness of those components and thus improve the reliability of the product.

Rick, thank you for your answer. I am wondering how the acceleration factors are identified, how their impact on inverter life are recognized quantitily, and how the equivalent life time is derived.