Selecting a VFD for 15kW Jaw Crusher Motor

Hi all, I’ve been struggling with a problem and could use some advice. I’ve got a fully electric machine powered by a generator, but I can’t get the generator to start the main motor — too much inrush current at startup. I already bought a soft starter GS-022 for the main motor, but it still wasn’t enough. I’ve been tempted to ditch the whole setup and just install a diesel engine with a different generator, but before I do anything drastic, I wanted to see if a VFD would help.

The idea is to wire the VFD only to the large motor and let the smaller motors start normally once the main one is running. If the big motor starts okay, would I still need VFDs for the other motors?

For context, the main motor is a 15kW, 3-phase, 220V unit driving a jaw crusher. The motor pulley is 178mm and the crusher flywheel pulley is 812mm. The flywheel is heavy, but everything spins freely on bearings and will be started empty — no rock load.

Thanks in advance!

Orson wrote:Hey Orson,
Good question. A soft starter typically reduces inrush to about 3–5 times the motor's rated current, still pretty high. A VFD is more effective in this regard, with starting current closer to 2–3 times rated.
For your 15kW 3-phase 220V motor, we recommend stepping up to a 30 hp (22kW) VFD to give you some overhead, especially with that heavy flywheel. The model would be GK3000-4T0220G.
You can find it here: https://ato.laisteel.com/30hp-vfd
Let us know if you need help with wiring or settings.

Orson wrote:Orson, VFD is the way to go with jaw crushers. Flywheel inertia + startup torque = soft starter struggling unless you grossly oversize it. VFD also gives you the benefit of speed ramping and protection settings.
Also, for your existing GS-022 soft starter, if you're planning to reuse it elsewhere, you’ll want a normally open contactor for bypass. That’s standard for most soft starter bypass configurations.

Appreciate all the feedback! Makes sense about the inertia and needing extra overhead. I’ll go with the 30 hp VFD and reuse the soft starter on one of the smaller motors. Thanks for confirming the bypass contactor needs to be normally open too.