Inverter Log

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Contacts

Yoonseo Kang - ykang404@gmail.com

Aaron Makaruk - aaronmakaruk@gmail.com

Tim Boyd - tboydlaser@aol.com

Matthew McDonald - msm235@gmail.com

Marcin Jakubowski - opensourceecology@gmail.com

Resources

Design goals, design paths, schematics, simulation results, layout, ... condensed here: Inverter

Log

October 10, 2012

Email Exchanges Aaron - no problem.

Yoonseo - I think we both agree using a digital sine wave generator is the way to go. I've seen it done with an ardiuno and i'm sure something simpler exist's on an IC.

Another possibility is to use a pulse width modulator IC. Texas Instruments designs a few, the SG3524 being one example. It's cheap and would simplify the design, however, I think something like this might be too high level and pre-packaged. The same argument could be made for the digital reference signal but I think the increase in build quality is worth it. Thoughts?

Buck/Boost versus Transformer: Component sourcing should be the same level of difficulty for both, I've managed to find sources for the electrical steel and magnet wire as well as the buck/boost converter main components. Although I'm curious about the cost's of each, I'll have to look into that more. I think fabrication is going to prove more difficult with a DIY Transformer, this would require either manually winding the bobbins or constructing a coil winder that can handle #4 to #10 wire and maybe some tooling to accurately punch out the laminations.

Have a good one, Matt

October 8, 2012

Email Exchanges

Good Evening Everyone,

I have a few questions regarding the inverter oscillator design and high voltage DC regulation.

Oscillator - I'm looking through Yoonseo's design [ http://opensourceecology.org/wiki/Inverter/Yoonseo_Design ] is the use of the Bubba oscillator set in stone? I'm reading through the WPI project report and it appears they had a good deal of trouble with it's operation. Would it be possible to go with a fully digital reference sine wave? Has there been any more development on the reference wave feedback control circuit? http://opensourceecology.org/wiki/File:06_Feedback_Circuit.jpg

DC regulation - With the need to accept a wide range of source voltages and output a consistent 120 / 220 VAC signal, has there been any thought into the need for a high powered buck / boost converter to acquire the needed 170 / 311 VDC? Another possibility is to use a multi-tap output transformer, I would be in favor of this route for the following reasons: 

1. Reduces the complexity of the output filter
2. Can be designed to replace the high powered buck / boost converter and therefore improving reliability by simplifying the over all circuit.
3. In the case of a shorted MOSFET or some other fault, will eliminate the possibility of high voltage DC present on the output signal
4. Output transformer can be be manufactured given a well made sheet metal press, various hardware and proper research

See this instructables link for a reference on a transformer coupled design: http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/

Also, in regards to the failing inverters already in place at FeF, has any effort been put into investigating the possibility of repair? If these are preventing collaborative production runs of the GVCS it may be faster to fix them in the mean time until this project is completed. Aaron, if you're open to the idea, would it be possible to send one of the failed units to Denver so I could have a look at one?

Have a good night, Matt

Hello Everyone


Does the inverter need to be grid tie now or in the future?

Tim Boyd tboydlaser@aol.com

The circuit for generating the reference sine wave is not set in stone. I prefer a fully digital reference sine wave in preparation for versatile operation. If we pursue the digital generation I assume we would just source the relevant integrated circuit?

No development on the feedback circuit to date.

Buck/boost converter considered, but not developed to date. Between the buck/boost converter and the multi-tap transformer, I am most concerned about ease of fabrication/sourcing and would like more information regarding that factor.

Best,

Yoonseo

Marcin asked to join this thread so he'll be in on all further discussion - Tim - being grid tied is not a priority right now.

Aaron

Introductory email between all project participants

  • To be done - 10/08/12
  • Introduce everyone
  • Let's discuss general inverter topologies to suit OSE Specifications
  • We will start an email chain discussing general inverter topologies (ex. full bridge, half bridge)
  • Let participants know that the email chain will be uploaded to the Inverter Log in a subsection.
  • Needs:
  • Input 72V DC
  • Output 120V AC at 60Hz pure sine wave with power rating of 5kW or 10kW [consider stackability].
  • OSE Specifications
  • These things are preferable but are less of a priority than function, reliability, and ease of fabrication.
  • Input should be flexible enough to accommodate a wide range of input voltages.
  • The output should be flexible enough to vary (ex. both 120 and 240 V AC)
  • Modular design - Example
  • Use of open source design software


  • Email was sent
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