Just in case anyone is intrested, here are some pix of my 100 amp DIY VFD being assembled. As soon as time permits i will post a video of the VFD in opperation. I still have to make a remote control pannel.
On Fri, 15 Aug 2008 03:19:17 -0700, with neither quill nor qualm, "azotic" quickly quoth:
Cool! It looks like the project is really coming together, Tom.
-- Challenges are gifts that force us to search for a new center of gravity. Don't fight them. Just find a different way to stand. -- Oprah Winfrey
The big power modules mounted on the heatsink - what are they and what did they cost?
Thanks,
Joe Gwinn
Just wondering, does the little bridge rectifier on the lower right of picture inv6 provide the power to the much larger switching elements on the heat sink. Is the large white cylinder in the last couple of pics the rectified DC filter cap? What do you calculate the ripple current in the DC filter cap to be?
Carl
Are you planning on making and selling the PC board? Components?
Wolfgang
Put this in context. What are you going to run with this?
Wes
Looks real nice! Also looks like something even -I- could put together from a kit. You going to offer plans/boards? Hmm, maybe I shoulda held on to one of those heat sinks....
Jon
Thanks, i plan on adding a jog and brake feature to the design which i think will be handy to have.
Best Regards Tom.
Progress !
Mart> Just in case anyone is intrested, here are some pix of my 100 amp DIY VFD > being
----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==----
---= - Total Privacy via Encryption =---
They are dual IGBT transistors also known as a GTR module. Basicly they are 2 NPN transistors conected in series to form a half bridge which means the are capable of switching both + and - DC power back and forth. You get AC output in the form of a square wave as a result. You can achive the same result by using 2 individual IGBTs.
The GTRs i am using have the capacity to switch 100 amps at 1200 volts, they have built in free wheeling diodes which cuts down on the component count. I bought these GTRs on ebay for $8.00 each, shipping was $7.55.
Best Regards Tom.
The output of the bridge rectifier is connected directley to the large white filter cap ( 2700uF @ 420Vdc ). I didnt do any ripple calculations for the HV dc buss since motors and transformers dont seem to have problem with ripple. However there are seperate regulated power supplies for the logic and gate drivers where ripple would be a huge problem. The large white filter capacitor at the end of the buss just happened to have the same center to center hole spacing as the GTRs which makes it possible to mount it right on the buss bars and eliminate the additional wiring that would be needed if i had to mount it elsewhere.
Best Regards Tom.
The thought had crossed my mind. If i do decide to sell circuit boards for this project there will be a parts placement printed on patern on the top side. I am thinking that building a board will work like painting by the numbers, you would place the parts U-1, D-3 etc. into the board with the locations marked U-1, D3, etc. then just solder them in place.
Best Regards Tom.
Motors, Welders, maybe experiment with makeing an electric go-cart. Being old school my thoghts were to make a VFD with way more capacity than i would ever need. I also want it to be repairable and user friendly. That is why i designed it using discrete components that are in sockets comonly availble from multiple sources at low cost. No custom sole source propiorty stuff for me. The design of the driver board allows for scaling up or scaling down the power, just select the right size IGBTs for the application. If you only need enough power to run a small motor you use small 15 amp IGBTs, if you want run a welder you get some 400 amp IGBTs.
Best Regards Tom.
Thinking about it.
Best Regards Tom.
Dont you just love it when a plan comes together.
Best Regards Tom.
On Fri, 15 Aug 2008 19:07:53 -0700, with neither quill nor qualm, "azotic" quickly quoth:
Au contraire, mon ami! I strongly suggest using sockets as you did.
-- Challenges are gifts that force us to search for a new center of gravity. Don't fight them. Just find a different way to stand. -- Oprah Winfrey
So each module is a a half-bridge containing two IGBTs plus some frewheeling diodes. What make and model?
The reason I ask is I'm designing a homebrew impulse magnetizer, to be built around three 2900 microfarad 350 volt computer electrolytics I got surplus somewhere (no longer recall when or where). In this case, the current is all surge and no continuous, and the modules I'm considering are Diode-SCR half-bridges. (IGBTs don't seem suitable.) The circuit protects the electrolytics from reverse voltage by returning the inductive kick to the capacitor with the correct polarity to charge it.
The surge current will be something like 3000 amps for 10 milliseconds. I'm still working out the details, such as how big a surge current is needed. Even if the SCRs and diodes are happy, the capacitors have a limit as well.
I got the circuit idea from an expired US patent, 4,258,405 to Steingroever. Steingroever uses Mercury-pool ignitrons, as nothing else will withstand the currents necessary to use pulsed magnetic fields to form metal.
For more information on metalforming, see US patents 5,586,460;
5,684,341; 5,813,264; and 5,953,805. Also see the website of Dr Steingroever's company: .They use very high voltages and small inductances, to yield very short pulses, the better to create the eddy currents against which they push to apply force to the metal being formed.
For our purposes, and with some care, the ignitrons may be replaced with big SCRs. But even the biggest of SCRs is a wimp compared to a big ignitron.
Richardson Electronics still offers ignitrons and hydrogen thyatrons:
But they tend to be expensive.
Joe Gwinn
A sine is not nessesary to run a 3 phase motor.
Best Regards Tom.
I am using Toshiba MG100Q2Y51A GTR modules.
Intresting project your working on, there are IGBTs that might work for your application but there going to be pricey. I did see some 600 amp IGBTs on ebay this week that were reasonably priced. If your going to buy some on ebay make shure you ask the seller if you can return them should they be blown. Some sellers are selling units they claim are tested but they are not. I had to return some that had blown gates and would not fully turn off.
Best Regards Tom.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.