PFC'd petrol generator?

[Faringdon]

Hi,
Supposing you have a petrol sinusoidal mains  generator, the typical car  "trailer" size.
Supposing that the PFC stage  input current (from the generator)  has a fair amount of harmonics in it, not as bad as Rectifier/smoothingCap, but not
a beautiful pure sinusoid current.

Will this mean more stress on the rotor bearings of the generator, compared to if the current was a pretty pure sinusoid in phase with the voltage?

And also what does the attached  current, if drawn from a petrol generator, do to the bearings of the genny?

[Zero999]

What  PFC stage? Are you talking about a generator supplying an ordinary capacitor & rectifier vs one with active power factor correction?

[Andy Chee]

Will this mean more stress on the rotor bearings of the generator, compared to if the current was a pretty pure sinusoid in phase with the voltage?

From the prime mover's point of view (i.e. the internal combustion engine), bad power factor is seen as extra horsepower and fuel required to overcome I²R losses along the length of extension cable to the appliance.  Or if you turn the equation around, bad power factor means less power available from your generator.

Either way, the losses will not be significant enough to physically damage anything mechanical.

And just to be clear, electrical harmonics does not create mechanical knocking or mechanical imbalance harmonics (not large enough to wear out a bearing anyway).

[Jeroen3]

Harmonics are additional currents in the stator/rotor, causing more heat. Derating is required when using non linear loads.
Sometimes, harmonics can induce current paths that goes through the bearings, this is very bad.

[Circlotron]

Absolute worst case it would cause some variation of torque absorbed by the alternator, but seeing it is probably a 2-pole 3000rpm machine, even with a sinewave load the absorbed torque would vary twice quite a bit as the machine rotated through 360 deg anyway. In any case, there is a single piston moving up and down like mad right next door, so if the alternator bearings can tolerate this, then any electrical load would be nothing by comparison I expect.

[NiHaoMike]

A teardown of a BMW i3 generator unit shows they do 3 phase PFC when rectifying to DC, of course they're trying to get the best efficiency possible on a given budget.