Power a AB Powerflex 40 VFD from a Roto-phase?

The Background…

We have a rural customer that has a single phase service and is using a roto-phase to run the 3 phase equipment.

One of the motors (a drag conveyor) requires speed control and is currently has a AB PowerFlex 40 VFD installed. During the installation of that drive 2 years ago, we were advised by our AB distributer that connecting the VFD to the roto-phase supply could potentially harm the VFD. So in order to eliminate that, we are feeding the VFD with single phase power using the 2 ‘true phases’ and not connecting the 3rd ‘manufactured’ phase.

The setup has been running relatively trouble-free for 2 years. However due to equipment additions, the roto-phase is too small, so a diesel gen-set was installed. The customer can now with an isolating transfer switch, select to use either the roto-phase or the gen-set, depending on the load demand. Since that installation, whenever we are running on gen-set, the VFD will trip frequently with faults F3, F4, and sometimes F5. If the power is coming from the roto-phase, there is no issue.

The motor in question is 600V 7.5Hp 7.2FLA. The VFD is a AB Powerflex 40 22B-E019N104. (600V 15Hp 19.0A Output). As you can see the drive was initially de-rated 0.5 for the single phase input. AB Powerflex 40 specs require de-rating to 0.35 (Knowledgebase ID#26098). The load is running roughly around 6.3A when the faults start to occur, which is around the 35% threshold so obviously this is the reason our faults are happening. The wrong derating factor was used.

Now for the real Question…

In order to correct this situation, we have several options. The most ideal, is to feed the VFD with 3 phase power all the time. The majority of the time, the gen-set is the power source, so clean 3Ph power is available. But in some situations, the roto-phase will be used.

We were warned initially not to feed the VFD from the roto-phase.

Why not?

Will the capacitance from the roto-phase harm the drive?

So am I reading this right, you have the VFD connected to 2 phases of the roto phase??

Not an expert nor am I familiar with that particular model of VFD but why are you supplying it from the roto phase at all? why not connect directly to the single phase line. The VFD's I have here will act as a phase converter as well as a speed controller. Sounds like it's just not happy with the power from the generator, not uncommon to get a fair amount of line noise from generators.
Not sure of the exact reason why you can't connect to the roto phase.

Put a scope on your genset.Last year we had similar issues with one of our gensets at a lift station and turns out it was output was no a sine wave but a sawtooth.

We had to bad power control and regulation boards.