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I'm using 2 x 400V caps in series. They are the same capacitors used on a 415V VSD I opened from a major and well known manufacturer. Can you tell me what's wrong with the inductor wiring? I'm not sure about the size and whether I made it large enough.
it looks to be a common mode inductor and they are supposed to be wired series opposing and it looks like you are showing the wires crossed to be series adding.
general rule of thumb is 1000uF/A, though you need to check the ripple rating that it is over 1.5 times the load current.
We already thought about that, but a large proportion of the motors that will be fitted to it are pretty cheap and nasty and can't be changed from 415V to 240V. I would actually prefer this option because the lower voltages would cause less stress on the motor insulation.
In the schematic you posted, you also show "COM" pin#21 wired to the Vss pin. It, COM, is the return from the IGBT's not to be wired to signal ground,Vss.
From what I could gather in the datasheet the only reason for the COM pin and Vss is so that you can connect a low value resistor between the two to detect overcurrent. I checked with engineers from IR and they told me that it was OK to connect the two if I didn't want to bother with this.
I know it might sound a bit odd that I would leave this out, but in the particular application it is better that the unit fails and burns out than trip on overcurrent.
(I'm sure I'm going to cop a bit of flak about that last line...)
it looks to be a common mode inductor and they are supposed to be wired series opposing and it looks like you are showing the wires crossed to be series adding.
general rule of thumb is 1000uF/A, though you need to check the ripple rating that it is over 1.5 times the load current.
Yeah, sorry about that. I must have swapped the pins while I was working on the PCB and it has done something funny in the schematic. It's not meant to be like that.
it would appear that he is a technician passing himself off as an engineer and got in way over his head on something relatively simple and is hoping to have us, some of whom are real engineers, bail his backside out.
one would hope he is not typical of the sort... I had one effectively call me all sorts of names one time until i proved him wrong on the point and he just jumped to the next point and started calling me names again.
and that was in a conference call with me sitting with my boss and his bosses... unfortunately they did not learn from it.
If you guys do this on your own, do you realize how much it will cost for certification of your design? To protect your self from law suits if there is a problem?
Hey guys,
Just so you know, I have a degree in Electronics Engineering. Oh, and I graduated with first class honours. I have been designing circuits for about 5 years now. I definitely wouldn't say I am an expert, but I can usually hold my own.
This is the first time I have attempted to build a VSD. Naturally I knew there were going to be problems. I didn't have much experience working with IGBT's, but I have learnt a lot. *Learning* is the key word here. You can't be an expert on everything. That's why sometimes you need to reach out to other people for help.
The 240V version works fine. I've had it running for over 2 hours straight. I wouldn't say this is a result that someone would get who is "way over his head". The real challenge has been getting the 415V version to work properly. It sounds very simple, but I have found that isn't the case. And in case you were wondering - I used the IRMD2336DJ for parts of my design. But it operates at 220V.
I have been talking a lot to the engineers from IR about these problems and this is the exact quote they sent me back in the email: "I can't find any inappropriate on the schematic." (I don't think English was the guys first language).
Thanks for your help guys. Unfortunately the problem hasn't been solved. I guess I'm on my own for this one.
Hey guys,
Just so you know, I have a degree in Electronics Engineering. Oh, and I graduated with first class honours. I have been designing circuits for about 5 years now. I definitely wouldn't say I am an expert, but I can usually hold my own.
well honours does not mean a hell of a lot in the real world aside for snowballing personnel weanies.
check your igbt speeds and delays - you are shooting through.
at that power level you do not need igbts, just use FETs.
what is the rating on the motor? while a VS drive can drive a 220V motor from a 440V line, the HF content goes through the roof as the current goes up quicker.
Some basic RC snubbers can do wonders for switching device longevity when working at the upper end of their working voltage ratings.
As far as where you sat honors wise I have met people with doctorate degrees specific to some of the stuff I play with just for giggles who can't figure out how some of it works.
So either I am some sort of mad scientist super genius or perhaps more likely what a piece of paper says you know doesn't mean diddly about what you actually do know and or can do.
For a few hundred dollars I can get a fully accredited doctorates degree online that will hold enough weight to get anyone to refer to me as doctor and listen to what I say as well even if I am just blowing smoke out my butt the whole time.
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