Thread: single to 3 phase vsd confusion.

Hi Pete,

Just for the record, it's apples and oranges, Graziano was discussing the difference in current between 2 pole and 4 pole.

My comments were discussing the difference in current between star and delta..

I'm not entirely surprised you didn't pick up on that difference.

Regards
Ray

received the call from the electrician regarding the cl-38a motor, though was unable to supply the details, the only other details supplied is that the
average amps are 6.4A / 3.3A.

No worries Ray, as I'm sure you know full well know Ohm's Law is a law dealing with resistance, any bastardisation of it is not technically Ohm's Law at all, indeed virtually no part of Ohm's Law is in any way applicable to AC motors from any practical standpoint. I guess that's unremarkable given that the gentleman who gave his name to it died decades before AC current was even invented! Nevertheless I can appreciate that it is sometimes a convenient way to think about the topic for those not properly familiar with the subject.

Pete

Originally Posted by Pete F

No worries Ray, as I'm sure you know full well know Ohm's Law is a law dealing with resistance, any bastardisation of it is not technically Ohm's Law at all, indeed virtually no part of Ohm's Law is in any way applicable to AC motors from any practical standpoint. I guess that's unremarkable given that the gentleman who gave his name to it died decades before AC current was even invented! Nevertheless I can appreciate that it is sometimes a convenient way to think about the topic for those not properly familiar with the subject.

Pete

Wow!... stunning statements...

Ohms law applies equally to AC circuits just as much as DC circuits.. Interestingly Ohms Law also has a equivalent in magnetic circuits.

Here's a question, what do you understand by the term VA rating?, and how do you calculate it?

Regards
Ray

G'day Ray, well I wouldn't say they're really very stunning statements at all, actually very basic electrical theory. I've said it above but will confirm it again, I'm not going to argue with you about this. This is Ohm's Law, as developed by Georg Ohm, V = I*R No more. No less. If you want to believe otherwise please feel free to do so.

As I mentioned, considering the problem in an overly simplistic manner is sometimes convenient for those who don't properly understand a subject, however the caveat in doing so is that while that inappropriate process may well provide a correct solution to that particular problem, it can lead to completely incorrect solutions to what, at face value, may appear quite similar problems. Indeed that has already happened in this thread.

Cheers,
Pete

*No eye rolls were harmed in the making of this post

Hi Pete,

I've pretty much stated the case, in as many ways as I can, for the reduced available power when running a motor off 240V when compared with 415V, and yes it's ohms law...

I don't see much point in continuing to feed your peculiar need to argue the point ad infinitum.

Good luck to you .

Regards
Ray

G'day Ray, I agree let's leave it at that, as I mentioned you can believe whatever you want, and I wouldn't let the fact that the rest of the world thinks something different worry you one little bit.

Happy Easter mate

Pete

Originally Posted by Pete F

G'day Ray, I agree let's leave it at that, as I mentioned you can believe whatever you want, and I wouldn't let the fact that the rest of the world thinks something different worry you one little bit.

Happy Easter mate

Pete

Some may say speaking for the rest of the world is a little over the top, you havent even asked them. At best its "the rest of the world minus one"

And a happy easter to you.

Stuart

Pete,
Back in post 36 you stated,

Originally Posted by Pete F

Ray I'm not going to get into an argument with you about this. If you feel a 3 phase motor behaves strictly according to a simplistic AC version of Ohm's Law, I'll leave you with it. I post to the forum to try to help others if I feel it may be of some value, and don't see the forum as a contest.

We are all here to have fun and learn from each other, if you feel you don't understand something or think something maybe explained wrong, ask a question politely of how the member thinks it works, and I am sure any members will accommodate you in explaining things.

We really don't need any members to have condescending or sarcastic posts, or having to have the last say because someone thinks there idea is right and the other person is wrong, it just spoils the thread.
This is a great forum, lets not let it drop down to the level of some other forums.

Over the years I have always found Ray to be nothing but helpful and knowledgeable, even if it means going out of his way to help. From what I know of Ray, he is an electrics guru and still does contract work in the field.

I am sure I speak for many other members here, in that we are not here to ague with each other, or win contests. We are here to talk shop among fellow enthusiasts.

I learnt a lot in this thread, but sadly it will now probably not be added to.

Dave

But hang on Dave, the rest of the world agrees with Pete.

Sorry Stuart, quite correct. Obviously I was speaking metaphorically to mean those who actually know something about the topic. I take it you'd like me to remove your name from the "rest of the world" list then?

Dave while it's good to see the clique back together, I would like to put this nonsense to bed once and for all, because personally I have better things to do with my time, and I'd be surprised if others don't too. Though obviously, as has been pointed out, I can't speak for others.

It would appear from the tone of responses that several days ago I may have said something that Ray has taken in quite a different manner to how it was intended, I have no idea how I pi$$ed in his porridge, but however, it was definitely not intentional. We had several similar threads running at the same time and quite a few crossings. I actually penned a lengthy PM to Ray to try to get to the bottom of it, however given the continuing tone of the responses simply thought "suit yourself" and deleted it.

Electronics is actually my trade Dave, and I then went on to study further until I (literally) ran out of courses to take at the Regency Park School of Electronic Engineering back when I lived in Adelaide. While electronics and electrical are really somewhat different fields, and VERY different trades, the electrical theory is of course the same, and I also found myself having to cross over into electrical when I worked in the marine field. Nevertheless on this board it would be Ray who I would turn to to fill in the very considerable gaps in my knowledge, as that was a long time ago and I have forgotten a huge amount in that time. Indeed I literally did turn to him on a number of occasions within these threads where I thought he may be more up to speed with the electrical code. I would never, ever , and will never hold myself up as a "guru" in any subject, least of all this one. I don't mention the above to "big-time" myself, that was merely my education and occupation, seemingly a lifetime ago, before a very radical career change, self-funded incidentally by working my guts out in that field.

Within the numerous threads I made a general comment, not really aimed at anything or definitely not anyone, that just because someone gets something to work in one situation, it doesn't mean it will work in another situation ie the case that it worked once becomes an internet fact. What I had in mind was that some of the configurations being suggested for VFDs within these threads seemed to be straying further and further from the manufacturer's recommended practices. That doesn't mean they won't work, but as a rule I try to K.I.S.S; ie do what the manufacturers' tell you, because the chances are they know a little about what they designed. The trouble is that somebody else comes along with a different manufacturer's product and it may not work in the same way.

So, what happened? Well I happen to agree with you Dave, and I don't feel sarcastic and condescending posts for absolutely no reason have a place here. I personally found Ray's post #26 condescendingly written to the board members here. Maybe it wasn't intended that way, I don't know, I frankly don't care. What I did care about was that it misquoted what I said above, complete with sarcastic "smilie". Now as you, of all people, know Dave, if you want to take a swing my way, that's fine, but as you know expect me to swing back! Because quite unfortunately it contained a number of errors, the most obvious being the reference to Ohm's Law. Now I knew what Ray meant. I think he knew what he meant, however as it stands that statement is wrong. I really don't care what anyone wants to believe, it is wrong, end of story. Georg Ohm's Law deals with resistance, yes there are other similar laws, but they are not Ohm's Law. Joule's Law for example was thrown in there for good measure a few posts ago (#65), for God knows what reason. Now the big problem with making incorrect statements about laws is that people then apply them in other situations that seem to be similar but are in fact not. Normally I wouldn't have said anything, but given the circumstances, intentional or not, of the context in which it was written I pointed that error out. Indeed it can be seen quite clearly that continuing to turn to Ohm's Law when it is not appropriate can lead to all sorts of trouble, as quite correctly pointed out by member "Graziano".

Now if in fact the big problem here is that I'm stepping on some self-proclaimed guru's hallowed ground, then I'm more than happy to simply not post from now on whenever I see a person with a problem regarding any electrical or electronic issue. At the moment I am frankly flat-out with work (working all Easter of course) and given that a number of my posts were intended to try to help you Stuart, I'm more than happy to spend my very valuable time on more enjoyable pursuits! I didn't join a machinists board to talk about electrical or electronics, but if I'm able to draw on almost forgotten experience to help somebody, especially join in with other members who have some knowledge of the field and collectively we can work together to solve somebody's problem, them I'm more than happy to give up that time and do the best I can.

It's always a shame to see the same old familiar names pop up the instant they smell some possible blood in the water and try to drag others down to their apparent level. But I should by now have learnt to expect nothing more Personally I'd put it behind and moved on, indeed going as far as encouraging comments about the powerpoint presentation, but if it's the last word you're concerned about David, then you should probably note that the author of post #62, the one that bought all this up again, was not myself

Now hopefully that truly IS the end of that

Pete

I would just like to set the record strait that Ray has not self-proclaimed to be a guru, that is of my opinion he is one.
From the work I have seen and seen him do and the help I have got, I proclaim he is one as he is very knowledgeable in not only that field.
Also from what I have seen he is both good at electronics and electrics, but I am not saying he is the best and we all should bow down to him, but if we cross reference any member here about something, it should be done politely as you would like done to you, not in a condescending way because you don't believe it.

Pete you do claim everyone is out to get you when ever something like this pops up, but it is not the case at all. We all like to live on a peaceful forum but you seem to take it those few steps further forward to get your point across, instead of doing like the rest of us and take a step back.
As for me knowing you, I don't at all, honestly, I gave that away a long time ago. Going by what I see on the forum I do find you get over involved, being condescending to members and you like to push your point across and have the last say. I am not the only one that thinks this way either, and I am not talking about any names in this thread what you call the old familiar names.
There is no clique on the forum. These old familiar names like to talk to each other and discuss tooling etc so they post a lot, and when they see stuff they think is out of line they speak up, thats all. Think of how a new member would read your posts and if they would join in, not likely. Thats not to mention how the person feels that you are addressing.

I thought I put my last post together in the best word possible for this situation as I was enjoying the thread and learning a bit from it. I did not attack you in any way, nor did I go after blood as you say. I just wanted to let you know yet another thread has died because you wanted to put your point across no matter what. Ray was putting out some good info even if you do say it was wrong.

Hopefully we can all move on and just remember the values of this forum and what it and it's members gives us.

Dave

Well said Dave.
Pete, I don't know if you have personally met Ray but I have been lucky, and I mean lucky to have spent two days at close quarters with Ray. The first thing you notice is what a nice bloke he is. I absolutely wouldn't use the word 'condescending' and Ray in the same sentence. Over the two days at close quarters I troubled Ray for advice and not once did he make me feel like it was too much trouble or that I was being annoying, instead he was always more than happy to stop what he was doing to give me a hand. Not everybody can articulate what they want to say in writing and I fear most people fall into this category on occasion, you and I included. I can assure you, from personal experience Ray does not deserve a tirade, well maybe tirade is too strong a word but on this forum I suppose your comments would 'almost' qualify as one seeing as how this particular forum is one of the few left where 'prima donnas' who seem to think that their opinion is the only one that counts, seem to leave us alone (thank goodness).
Last thing, for every action there is an equal and opposite reaction, Ray reacted, appropriately. This is just my opinion, which may be way off base but is still, just my opinion.

Phil

I have followed this thread for two reasons. Firstly I am most interested in the option of using VSDs to drive 3ph motors from a 1ph supply. I would like to return to some of these aspects in a separate post.

Secondly the debate over various aspects has been.......interesting.

I participate in another section of these forums where debate seems to all too easily become heated. In fact the moderators have had to step in on a number of occasions deleteing posts, issuing thinly veiled cautions and at times weilding the axe. I would not wish to see that here. An unfortunate outcome is that one or more parties go off in a huff!

To some extent heated debate comes about because of a driving passion within the people themselves. That is coupled with the written word which so often does not convey our full meaning. While ever we can keep it civil the thread does not degenerate into a mele.

I am impressed by the amount of knowledge displayed in this thread. Let's leave it at that as I would like to get back to the original post shortly.

Regards
Paul