Variable Frequency Drives and Generators

Short answer - yes.

Yair...Thanks.

VFD's are often used just for their "soft start" capabilities. If I understand your application correctly, a VFD should work for you.

The VFD draws current as an uncontrolled rectifier so the current has high harmonic content. If you look at the rated input current to the VFD compared to motor current you will see what I mean. You then need to select a generator capacity based on this kVA requirement but I would advise you to double check with the generator supplier.

Adding a choke option can reduce this RMS input current.

Years ago, on a similar application, I was advised to use a generator where VFD load was only 25% of total load, or 40% when choke is used (lower harmonic content) as otherwise the windings would end up in danger of being damaged.

Maybe you can soft start, then, when at speed, inhibit and disconnect VFD and connect dol, as you similarly described. Shut down the inverter electronic inhibit input 20mS or more before breaking main motor poles to avoid VFD stress. This would appear a practical solution at low risk to your gennie.

Thanks for the link. Good answer and I hope my comment proved useful, too.

As I say, selection needs checking with the generator supplier, a choke is always a great benefit on most smaller VFD's when you have a limited or weak power supply as they normally have little or no choke as a standard.

you can use a soft starter.But there is a requirement of starting torque for every equipment and torque reduses as square of voltage.So a minimum voltage is required to ensure starting the load.based on this generator can be sized as with smooth increasing of voltage starting current is also controlled

Most soft starts may need 2 to 3 x flc on starting even on light loads