3 Phase Generator question

localbroadcast said:

The purpose of this thread is just to discuss that option, because from my research, it doesn't seem like anyone has exploited this option with this type of motor yet. maybe for good reason, but I'd like to examine the option anyways.

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https://lmgtfy.com/?q=using subsynchronous vfd for vehicle regenerative braking

Was that supposed to be helpful?? funny?? sarcastic??

It is what it is.
Either My Google Foo > Your Google Foo, or you didn't research the right words.

Was that supposed to be helpful?? funny?? sarcastic??

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I think his intention was to show that what you are working with is a well known concept and that it has a rather limited applicable value for doing what you want.

That is to say it's overly complicated and has a overall poor generating ability for what goes into the design.

A motor with either a permanent magnet or electromagnetic rotor make the overall regen part of the system substantially easier to work with along with greatly boosting the mechanical to electrical conversion efficiency during regeneration.

Basically what you are wanting is not a unknown concept. It's rather well known and proven to be not very effective.

tcmtech... I didn't happen to come across any information saying that. Did you? It would be nice if you provided a link to somewhere showing that SCIMs are not effective as generators. I've read a whole lot of pages about this topic and didn't come across anywhere saying that.

I worked at allen bradley building large 5000 HP VFD's for years. Don't worry about me.. I know VFD's inside and out.

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But I thought you were a VFD system expert which I assumed meant you understood how they interact with induction motors of various designs in all degrees of power, regen and braking modes and their related ranges and limits of operation and efficiency in them.????

Well, that's what happens when you make assumptions. You're wrong more times than you're right. I said I built VFDs and that I know them inside and out. I didn't say I designed them or know absolutely every efficiency curve that exists for every VFD / Motor combination that exists. Stop being ridiculous. The VFD's I built were all for 3 phase asynchronous motors in the 5000 hp range. Most were 6 pulse but there were some 18 pulse machines. None of them had regen modes. Some had large resistor banks for braking.

Since I'm building a VFD for an electric vehicle using a 3 phase squirrel cage induction motor... I thought it would be nice if I could get some energy back through regen braking. Even if I can get a small percentage back, it's better than nothing. So don't be so negative bro. move along.

Read it and weep.... Finally dug up this textbook that I haven't looked at in years... Here's the information that I was looking for the whole time... It explains exactly what I've been saying, and it doesn't say anything about it being too inefficient to be worthwhile. Infact, quite the opposite. It actually says that this is a very good setup for getting power back with regenerative braking of a squirrel cage induction motor.

Then build it...
'nuff said...

I'm on it. Thanks for the help and encouraging words.

It explains exactly what I've been saying, and it doesn't say anything about it being too inefficient to be worthwhile. Infact, quite the opposite. It actually says that this is a very good setup for getting power back with regenerative braking of a squirrel cage induction motor.

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No one said it couldn't be done. The points being made were more to the effect of is the added complexity and related components to get a induction motor to work that way going to be offset by energy returned or saved and if so what is the realistic return on investment for doing so.

Adding a $1000 worth of extra electronics in order to get a couple of tens of cents worth of power returned or saved at best per battery charge and related driving cycle may not work out to being worth anything in the end.

You pretty much hit the nail on the head there tcmtech.. The added cost for electronics to add the regenerative function to the drive will be small. That's the whole reason why I'm investigating the option. I will be building the VFD to drive the motor anyways, the regenerative function is simply additional code in the microcontroller and the charging circuit. Adding code doesn't cost anything, and a charging circuit can be built relatively cheaply.

When gaining efficiency in an electric vehicle, it's not so much the savings on electricity cost, its more for added vehicle range. I dunno where you're getting 1000$ worth of extra parts from.... The most expensive piece of the VFD is the SCR's, IGBTs or MOSFETs.. which won't be anywhere near 1000$, and I need those to drive the motor regardless if there is regen braking or not.

I'm done arguing with you about this. You obviously feel like you know everything about this topic already.. So have fun with yur windmills bro.

Wait a minute....
You're VFD "expert" but have never heard of switch mode power supplies? How does that work?
And if you're wanting to charge a bank of batteries at any decent clip, that LM317 will charge a motorcycle battery....in a few days... Making a high amperage regulator circuit, much less one that will charge multiple batteries at high currents and higher voltages and keep them balanced ands keep from overcharging them and cut out when input power gets too low and cuts itself out under fault conditions... Now you're getting into hundreds of $$$ worth of circuit if not more.
So, I'm thinking "show me the money". I'm not a VFD expert, but I'm pretty damn good with SMPS's and from that alone I can infer a lot about VFDs in general.

Show us a schematic and parts list relating to the size of system you think you would need for an EV to do as you are claiming.

Thats the common language we speak here. Schematics and actual parts.

As far as writing code goes you can write all you want but at some point there still has to be actual power handling components and circuitry that does the actual work of which when you get to the sizes of components that are necessary for a full sized vehicle type EV drive system those parts don't come cheap and adding just 1 or 2 specific items can in fact easily add $500 - $1000 to a already expensive circuit system.

As far as my wind power goes believe me I learned it the hard way that overly complex does not hold up well plus it gets expensive real fast which quickly puts the ROI well beyond cost effective for anything more than a hobby/learning experience.

Been there done that and paid the bill.

BTW your 'read it and weep' post attachments relates to a complex and old style constant voltage constant frequency AC to variable voltage variable frequency AC SCR based drive system not a DC to AC VFD system that a EV would use. I know the difference.

Yea I wanted to weep but not for the reasons you intended.

Was showing you an scim used as a generator at variable speed you fool.


Vfd expert? If I were an expert I certainly wouldn't have to ask questions to the likes of you. Your words not mine.

Done building it yet?

Ya it works great. Thanks for all your sarcasm it seems to have given the system a 10% boost on energy recovered during regen mode.

Vfd expert? If I were an expert I certainly wouldn't have to ask questions to the likes of you. Your words not mine.

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But........

I worked at allen bradley building large 5000 HP VFD's for years. Don't worry about me.. I know VFD's inside and out.

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So......... What were we supposed to think?

Worked on the R&D of this:

lol holy **** skimask that video is kinda funny.. Every 3rd word the guy says is something most people wouldn't understand.. It's hard to tell if they are actually talking about a real product or not. Especially at 1:42 where he says "dingle arm"..

And no.. I did not work on that product when I was with the company. I worked in the assembly of VFDs, not the r & d of anything. I wasn't part of the engineering or design team, I simply assembled them. Sorry if by stating that I knew them inside and out it came across as me knowing absolutely everything about them. I should have clarified that. A more accurate statement is that I know the schematics of the models I built very well and have a sound understanding of the theoretical operation of them, but I don't know the in depth information about the voltage and current waveforms and triggering patterns. I saved a copy of a schematic from one of the models which is a great reference for me.

I know enough about 3 phase inverters and rectifiers to understand how to use them and trigger them for use in a VFD that is driving a motor in forward or reverse, but the knowledge I lack is in using them in operation as a generator. I don't want to come across as a know it all and I'm sorry if I have. I am able to recognize my shortcomings and I hope that you guys can as well. None of us know everything, and we can all learn something new. Instead of bickering and trying to turn this into an argument about who's right and who's wrong, it would be nice if we could work together and share our knowledge in order to have a productive outcome to the conversation.

Anyways... Check out the motors I just picked up. 80$ for 2 of them brand new... One of the reasons I chose to work with a SCIM and not a permanent magnet or wound rotor motor.. these can be found extremely cheap! They won't be powerful enough for a full size electric vehicle, but they are big enough that I can build a VFD to run some tests with, get some data, and learn from for when I scale up to a larger motor.