Re: [pvusers] Re: Question on inverting DC to AC

["Scott Willing" <willing@mb.sympatico.ca>]

Thanks very much for your post Subu.

In the late 80's I had the privilege of contributing to the design of 
a unique SPWM inverter controller ASIC that was, amongst other 
things, specifically intended to provide multiple output options, 
e.g. 50/60/400Hz fundamental frequency, via a few control pins.

Unfortunately the company directors were bent on bringing complete 
UPS products to market to compete with the established firms in the 
field, rather than selling the IC or licensing the design. Tough path 
for a small Canadian start-up. Also, "alternative" power was not even 
on their radar screen, or they might now be part of the Xantrex 
empire. :-)

I often wonder what happened to them (I believe they simply faded 
away) and I often wish I had a few of those chips to play with. 
Similar functionality could be now be provided with a 
microcontroller, but the ASIC used a unique means of developing the 
SPWM control signals that still has appeal today.

Best regards,
Scott Willing 


On 10 Sep 2002 at 10:30, subu.muthu@philips.com wrote:

> Hello: I have good experience in working with the inverters both
> standalone and utility interactive types. It is not easy to modify a
> 60Hz inverter to 50Hz inverters because you have to deal with changing
> the fundamental 60Hz (either sinusoidal or modified)  waveform
> generation to 50Hz. With the current inverter technology, it is
> commonly implemented by firmware/software with microcontrollers.  With
> the microcontroller implementation, technically one can modify the
> software code to make the inverter to generate 50Hz waveform with the
> existing hardware and filter components, and the same inverter
> platform can be used for different markets such as Japanese/North
> American with different firmware.
> 
> However, for you, you need to have the access to the program (source
> code) first,  and no inverter manufacturer supplies this. Code reverse
> engineering  is difficult.  In addition, you have to deal with the
> timing issues, programming the micro etc.
> 
> The same thing applies for the voltage, however, technically it will
> be easier to adapt a 120VAC inverter to 100VAC inverter. This can also
> be achieved by modifying the software (timing is not an issue, you
> have to modify the modulation index)
>  or just by adding a step down transformer (This is not the solution
> because  of the added cost with the magnetics).
> 
> In addition, You may have to make the inverter to comply with the
> Japanese utility and safety standards if required.
> 
> Hopefully this helps.
> 
> Subu Muthu./
> 
> 
> 
> 
> 
> 
> 
> Christopher Witmer <cdwitmer@spamcop.net>
> 09/09/02 05:48 PM
> 
> 
>         To:     pvusers@crest.org
>         cc:     (bcc: Subu Muthu/BRQ/RESEARCH/PHILIPS)
>         Subject:        [pvusers] Re: Question on inverting DC to AC
>         Classification: 
> 
> 
> 
> I'm trying to build a system for use in Eastern Japan, which is
> 50Hz/100VAC. Inverters designed specifically for the Japanese market
> are more expensive than others, such as 60Hz/120VAC inverters, since
> the Japanese market is small. If I could obtain a (relatively) cheap
> inverter designed for the USA market and then get it modified for
> 50Hz/100VAC operation, that could be a viable solution for me. Does
> anyone have any idea about how difficult it would be to make such a
> modification to an existing inverter?
> 
> Thanks,
> 
> Christopher Witmer
> 
> Robert Warren wrote:
> 
> >  If you were building an inverter (and I know you aren't from the
> question you asked), then it is no big deal to step up the DC voltage
> with a bridge rectifier/capacitor circuit: a lot of inverter
> manufacturers have entirely gotten away from using big transformers.
> 
> 
> 
> 
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