Inverter generator AC plug Neutral

**RCinFLA** · May 5th, 2006, 19:04 PDT

Does anybody have a schematic or direct knowledge of the inverter output design on inverter generators.

I have a Yamaha EF3000sei. As an EE, I expect the pulse width modulated inverter bridge does not allow for direct connection of neutral side of 120 vac plug to ground as is required for SW series inverters connected to house wiring.

The service manual shows testing of the three phase rectified alternator at full RPM to produce 200 to 240 vdc. This would be inline with a full wave push-pull bridge FET chopper, meaning neutral is not groundable.

It is possible if the neutral is grounded the isolated power module will float up and down along with the 60 Hz output. I am concerned about possible effects of stray capacitance from power module/alternator coil to ground if this grounding of the neutral side of plug is attempted. (similar problem the small stand-alone inverters have). Other likely issue is perhaps bypassing half of a ground center tapped inverter bridge output filter. Yamaha's official answer is the inverter generator can not be transfer switch connected to house electrical panel and is only intended for direct plug-in connection to individual appliances.

To be safe I am putting the Yamaha output through an isolation transformer prior to AC2 input on SW inverter. I can then safely tie SW neutral to breaker box neutral which is ulimately ground bonded at box.

To me, all this extra work/expense is worth the benefit of the very quiet generator.

**Robin Gudgel** · May 7th, 2006, 17:22 PDT

Generators as a rule already have their neutral bonded to the chassis frame. I have not heard of a problem connecting an inverter/generator to an inverter/charger. They workk great. I've talked to probably 100 people that use this type of generator.

**RCinFLA** · May 7th, 2006, 17:36 PDT

Generators as a rule, are not inverter generators. With a scope I see equal and opposite sinewave at half the full output from neutral to ground and hot to ground.