I apologise if you are fully familiar with dual voltage rated 3ph motors, and I add the following as I know there is a lot of confusion about it. I’m deliberately over simplifying it and trying to just focus on the bits that are relevant.
In 3 phase supplies you have three live wires that each have a voltage of 240volts, a neutral and an earth. Each live wire although at 240 volts is operating out of phase with each other. I won’t go into the technical stuff about what this means. However, the practical side of things means that if you put a volt meter across any two of the three live wires you will get a reading of 415V. This is called the line voltage, and is why standard 3ph is stated as having a voltage of 415v.
If you take one of the live wires and check the voltage with the neutral wire using a voltage meter you will see 240V, this is called the phase voltage.
A normal domestic supply to a house in the U.K. is provided with one of the live wires, a neutral and an earth. The only difference between this and an industrial 3ph supply is that you don’t get the other two line wires. To measure the voltage you check the live and neutral and see 240V, hence it’s called 1ph, 240V.
How is this relevant to 3ph motors? Well we now need to consider that not all countries operate with the UK voltage of 240V. In the USA the phase Voltage and hence the line voltage (3ph) is lower. The line voltage is typically 220V. Just over half that of the U.K. rather than make 3ph motors specifically for each countries line voltage, they can be made such that by swapping a couple of links in the connector of a motor they can be made to run at different line voltages with no adverse affect.
A dual voltage motor can be made to run at a line voltage of either 400 or 220V - so it will work in both the U.K. and USA for instance. It requires all three live wires, 3ph, to be connected to run at either of the voltages. It will not work on standard single phase.
An standard inverter takes standard single phase, and converts it to 3ph. It does this by literally chopping up the voltage, changing it slightly and then smoothing it out to create 3 live wires. In doing this, the voltage is reduced in each of the three wires. So, instead of standard U.K. 3ph which has a line voltage of 415V (measured across any two live wires) it actually has a line voltage of c220V or something very close to that in the USA.
To use an inverter is very easy. You need a dual voltage motor. The 3ph motor has to have the links changed so that it’s in the low voltage mode, and then it can be connected to a standard inverter.
A fixed voltage motor that states it will just run on 400V can actually be made into a dual voltage motor. It’s not something that anyone nit familiar with motors can do, but something a motor rewinding company can do for you easily. However, the cost can be similar to buying a new dual voltage 3ph motor for small motors (typically what most of us will come in contact with)
