Sine filter for PWM inverter output
Sine filter for PWM inverter output
(OP)
Does anyone have access to design rules for sine filters for PWM outputs? Or - almost equally good - typical values for L and C versus U, P and f-max? Topology and voltage drop at rated load and frequency also appreciated.





RE: Sine filter for PWM inverter output
Not very efficient but very effective. Ramp, square, PWM, etc. as the input, but always a sine wave output. Most of this literature will be found in the 'old' section of the library,not much on the web. Good luck.
RE: Sine filter for PWM inverter output
My web search brought me to some "New Age Designs" claiming "overunity", which seems to be a new word for Perpetuum Mobile. It would be extremely nice if it works, but there is one catch - the output from an ordinary frequency inverter needs to be variable and the circuits shown are working with a fixed frequency.
There is one thing that pussles me; You say that you built one such circuit at school and that it was not very efficient. All hits on the web claim that the circuit is "overunity" which is another way of saying that efficiency is more than 100 percent. And that is not bad at all!!!
Still waitng for some down-to-earth thumb rules for sine filters...
RE: Sine filter for PWM inverter output
RE: Sine filter for PWM inverter output
What happens to electrolytics connected to AC without a DC bias?
Fizzzzzzzzzz..............Ka-booom!
I'm amazed you didn't learn this trick in college. We sure did!
Additionally, electrolytics have such lousy tolerance control, high ESR, and ESL, that you could not seriously consider them for a power filter.
Use polypropylene film types for this sort of application. They have better impulse rating, are normally self-healing, have low ESR and ESL, and are designed for AC service.
RE: Sine filter for PWM inverter output
BTW, connecting the electrolythics back to the DC busbar does bias them so they dont explode. Ripple current is still an issue, though.
RE: Sine filter for PWM inverter output
http://www.transcoil.com/documents/KMG-Brochure.pdf
for MotorGuard Sine Wave Filter
or
http://transcoil.com/documents/I_O_M_Manual.pdf
for MotorGuard Sine Wave Filter and its specifications what they typically include
RE: Sine filter for PWM inverter output
RE: Sine filter for PWM inverter output
Why should I rephrase my question "in standard filter terminology"? (I guess that you mean number of poles, filter type, passband ripple, slope and the like, but I do not think that this would lead to the kind of answer I am looking for).
I asked for design rules for sine filters for PWM inverter outputs. There are many such filters available - and I have used several brands - but since they seem to perform quite differently with respect to losses, resulting waveform, dynamic performance, space and cost, I am interested in getting information from as many quarters as possible so that I can find out what design parameters have been important for different producers.
So I repeat: I humbly asked for topology *and* design rules. If anyone have such available.
RE: Sine filter for PWM inverter output
Basically the filter topology will be derived from
1-how far you pwm f is from the frequency to achieve
2-If your Pwm'ed signal is Sinus or not
3-If you are running at constant speed or variable speed
4-What distorsion is to be achieved
When the filter topology is designed then to make it work is another story.
I did find that working ahead the filter (ie having a high freqency pwm and already sinus shaped signal) was helping a lot but thats kind of obvious)
I am not sure I helped but if you are more precise on your application I could try to be more efficient.
Good Luck
HS
RE: Sine filter for PWM inverter output
I think the problem in getting the response you asked for is that the parametrical and topological detail are within the domain of "proprietary" information ... and manufacturers of such filters are not inclined to give away the fruits of their labor and the keys to their stores.
I know you can appreciate their concern.
One thing I noted in your original post is a lack of definition as to the fundamental frequency range over which the VFD would operate..... and the switching frequency. With regard to the latter... does the switching frequency remain constant.... or is it variable; and if so, over what range.. One other consideration not set forth in your original post... is the results you would expect to obtain .... yes, you want the voltage applied to the motor to be sinusoidal .... but must it be 100% pure... or is some distortion acceptable? and if so, how much.
I also have a curiosity as to what precipitates the need for such a filter.... that is, what's driving the quest ?
Unless you are seeing absolute precision, I think that a Pi type type filter would accomplish the task with acceptable results.
Kind regards,
jΩ
RE: Sine filter for PWM inverter output
The reason for my question is that many manufacturers of PWM inverters claim that they can deliver "pure" sine waves by adding what they call "sine filters" to their inverters. Different manufacturers have different price tags and differing sizes. Some need filters that are almost as big as the inverters and certainly heavier, while others have less weight. Common for the manufacturers I have talked to is that they never disclose such data as waveform distorsion. Some say that there is no voltage drop in their filters and some admit that there is. ABB has, for example, introduced their "Step Up Filter" which - in fact is a filter and an auto-transformer that restores the voltage level.
I have not specified frequency range and carrier/switching frequency simply because I am talkin about ordinary motor drives and I expect those guys (and girls) that have anything to contribute will know those parameters. Also, I have not included residual distorsion because I have no idea what could be expected under all operating conditions. All I can do is refer to manufacturer's specs - and hope that they are good enough.
Finally. EMC considerations, motor losses, motor sound, bearing problems and insulation issues (in small motors that simply can't be delivered with special insulation) are some of the driving forces behind the quest.
So, I still humbly ask etc...
RE: Sine filter for PWM inverter output
It has a topology and calcultations
http://decision.csl.uiuc.edu/~ksinha/teleops/files/pape...
Rodar
RE: Sine filter for PWM inverter output
RE: Sine filter for PWM inverter output
http://gdansk.bradley.edu/iecon02/limited/cdrom_backup/...
It concerns filtering to the fundamental
Rodar
RE: Sine filter for PWM inverter output
Very useful link.
Perseverance pays!
RE: Sine filter for PWM inverter output
What an informative paper. Thankyou - an ex-colleague will receive that link on Monday, to his pleasant surprise.
cbarn,
Apologies, only read half your post re. electrolytics to DC bus.
RE: Sine filter for PWM inverter output
"Dis 1" is also a Du/Dt filter ... Not a Sinus filter ...
But a good paper, none-the-less.
jO
RE: Sine filter for PWM inverter output
"Dat 1" is sine enough for me - excuse me fine enough...
RE: Sine filter for PWM inverter output
Sorry jb,
Why should I rephrase my question "in standard filter terminology"? (I guess that you mean number of poles, filter type, passband ripple, slope and the like, but I do not think that this would lead to the kind of answer I am looking for).
///Normally, the standard terminology is used to facilitate an effective communication in specific engineering areas, avoids ambiguities and removal of posting in this Forum (as mine for example).\\\
I asked for design rules
///There are various design rules, e.g. design procedure, specification, description, guide, handbook, etc. None of them explicitely have been posted yet. Are you abandoning these?\\\
for sine filters for PWM inverter outputs. There are many such filters available - and I have used several brands - but since they seem to perform quite differently with respect to losses, resulting waveform, dynamic performance, space and cost, I am interested in getting information from as many quarters as possible so that I can find out what design parameters have been important for different producers.
///Often, design parameters and specific values, included graphs tend to be proprietary.\\\
So I repeat: I humbly asked for topology *and* design rules. If anyone have such available.
///More detail information what is actually requested would help.\\\
RE: Sine filter for PWM inverter output
If I ask the question in a manner "approved" by you. Will you give me the desired answer then? Or what are you aiming at?
RE: Sine filter for PWM inverter output
RE: Sine filter for PWM inverter output
If I ask the question in a manner "approved" by you. Will you give me the desired answer then? Or what are you aiming at?
///I just asked for clarifications of a rather different terminology from industry standards, dictionary, and manufacturing expressions that the original posting included, e.g. design rules, "sine filter", etc.
I provided references, e.g. Standard Handbook for Electrical Engineers that was unfortunately removed from this thread. Elementary filter design and numerous filter design software include a design of a filter that passes a single frequency waveform, e.g. 60Hz, in ideal case. In practice, there will be the product tolerances, interface parameters, ranges, physical dimensions, environmental qualifications, etc.\\\