3 Phase VFD supplied by single phase - de-rating

[Anguz]

Did you lift the center tap on the 110v side

 

[Agroshield]

...reverse wiring a 110v site transformer which did not work for me. The MCB immediately tripped...

I do not know if it is relevant to the tripping issue, but 110v yellow transfomers are described as 'centre tapped to earth'. In effect, it means you can only get a 55v shock from them. Maybe that part of its construction is what is causing the problem when used in reverse.

 

[Pete.]

Did you lift the center tap on the 110v side

Yep gotta lose the centre tap or you're sending supply juice to your earth.

 

[Smouser]

Thanks @Anguz @Agroshield and @Pete.
I did not know about the centre tap, I will revisit the transformer rewiring soon and post some photos for advice once I have the transformer open.

 

[GRW]

Sorry if it's a bit off-topic....
I freely admit I know next-to-nothing about VFD's, and have never reconfigured an electric motor from Star to Delta or vice-versa....
But I've reconfigured lots of (12-wire) alternators from (Series) Star to (Series) Delta.
In Star config the alternator is 3-phase, with each leg of the Star giving an output of 400v between each phase (& each phase being 120-degrees from its counterparts). Between any one leg and the central Star point (Neutral), you get 230v. Generally Neutral Star point is linked to Earth as well, to ensure zero Potential between N & E.
In Delta configuration, you get single phase output by picking up a Live from one "corner", and Neutral from another (the third corner is not used).
In Delta, an alternator needs to be de-rated by one-third (I believe due to the higher current at 230v).

So, with a motor load instead of an alternator supply - doesn't this mean that for 1ph use it too must be in Delta configuration??

 

[Pete.]

Usually if you're relying on a steinmetz connection you would use it in Delta configuration, yes. Having said that, I puled a 3 phase motor out of a barrier closer that was using it in star, but the loads were very small.

 

[mattg]

I have done what hopefuldave suggests a few times with great success. I now have three phase so there is at least one spare single to three phase inverter kicking around if it's of interest. Think it's around 7kW.

 

[Smouser]

I have done what hopefuldave suggests a few times with great success. I now have three phase so there is at least one spare single to three phase inverter kicking around if it's of interest. Think it's around 7kW.

If I can't get this VFD going I will need another solution. Your 'spare' inverter might just be the thing I need!

 

[mattg]

If I can't get this VFD going I will need another solution. Your 'spare' inverter might just be the thing I need!

Great. It's actually a lot larger, 23kVA downrated to 14 ish