Stepping may well be stepping. Without spikes no problem as long as the voltage fails to make it to zero crossing. Triacs for voltage control have been known to cause problems for modified sine waves.
3phs VFD's use an FM modulation technique for motor control. If one uses the same method filtered with capacitors you would have an almost true sine wave without the losses associated with controlling a wave form using transistors in analog mode.
The motor control part of an inverter generator seeks to maintain the DC internal bus voltage. If the voltage can not be maintained the overload condition is tripped. On an inverter a dip in voltage of this bus trips the overload switch as well. The only difference in design between an inverter generator and an inverter is one uses an ice generator and the other uses a DC to DC converter to supply the internal bus.
On one salvaged inverter generator, the generator part produced 48vac at slowest motor rpm. The eco switch is intended to be used to stop motor catchup when a load is demanded. When the eco setting is switched off the generator produces the bus voltage at all times, rather than running at a lower than need voltage unless a demand is measured at the bus.
On 03/13/2011 11:10 AM, Tom wrote:
I just started up my EU2000i and looked at the output with my scope.
The output is a nice sine wave with very little visible stepping. I think what wasn't pure sine wave may be noise due to my setup.
-Tom
--- In electricboats@yahoogroups.com, "Myles Twete" <matwete@...> wrote:
>
> Great comments and questions Kevin…I haven’t looked at the AC output myself, but would like to understand it better.
>
> You touched on it, but it helps to point out that what really distinguishes the Honda and other similar quiet inverter gensets is their decoupling motor speed with output waveform. By generating a high voltage and efficiently converting to and maintaining a HVDC bus, then following up with an inverter output stage, these generators don’t have to run the motor at constant speed to maintain 60hz output. AS you correctly pointed out, many AC loads are quite tolerant of some waveform distortion and so that’s not the selling factor for these inverter generators as much as the quietness and efficiency. However, they go together---seeking quietness, there was a desire to slow down the motor under low load---and to do that, they justified splitting the electrical generation portion from the AC conversion portion---and at that point, devoid of any need for AC output to track a motor’s speed, the creation of a very clean AC waveform is easy with electronics and adds another selling point. I would guess that these inverters use a 10-bit reference for the AC waveform (0.5v max stepsize), but probably even a 256-bit reference would offer “clean†power (4v max stepsize).
>
>
>
> -mt
>
-- Ubuntu10.04, Acer AspireOne, Virgin Mobile 3G Broadband2go. Doesn't get any better than this!
No comments:
Post a Comment