Inverters....

[Tiny Spark]

Well you were right darkwood this thing is opening up more questions than closing off answers!!

So heres the update:
Went up to check voltage bands of the motors.
Delta: 380-420
Star: 660-720

So anyways curiosity got the better of me and I decided to check the wiring of each motors terminal blocks.

So first units motors were both wired in delta the same as the one motor I had checked before.

2nd unit first in delta (one i checked yesterday) and the second in Star!!
This is obviously a problem!

3rd unit both wired in star.

So now I am left with several questions the top of my list being who and why!!

Moral of the story and personal lesson for me:
Never assume things have been done properly!

 

[Darkwood]

The motors may be wired according to the rating of the windings they have, just because you have various connection set-ups doesn't mean they are wrong, you need to check that the star or delta connection is correct regarding the individual motor , if motors have been changed at different times and/or sourced from diferent companies it may be likely you have a mixed bag of winding ratings.

 

[Tiny Spark]

The motors may be wired according to the rating of the windings they have, just because you have various connection set-ups doesn't mean they are wrong, you need to check that the star or delta connection is correct regarding the individual motor , if motors have been changed at different times and/or sourced from diferent companies it may be likely you have a mixed bag of winding ratings.

Hi Darkwood,
No they are defo wrong according to the motor rating plates.

However I believe the reason they are wrong is because if the above reason.
I had a hunt around and found a old unit with a original motor, These were rated the total opposite of the new ones (The Delta winding was higher than the star).
So my best guess is that whoever changed them just swapped a old one for a new one without checking the rating plate and wired it the same as the original.

 

[Darkwood]

Well if they wired to the wrong voltage on the plate you have your answer and its big questions to the so called Engineer who replaced them and doesn't know the basics of his job!!! If it is as you suggest above you may score yourself some brownie points and a gold star here... a few of us did query t on page one for this very reason and now you understand why

 

[Tiny Spark]

Yep, Like I said lesson learnt there for me.
I never even thought of checking the motors terminal boxes, Its one of those things I just assumed to of been correct but well there we go.
Interestingly there was a older motor which had been replaced at some point which was also wired wrong so god knows how long that had been like that!

Still the whole thing has been of benefit to me as I have learned a little more about inverters and drives so cheers all for your input

 

[Darkwood]

So just to clarify the original motors were 400/690 and correctly wired in delta, then the replacements were 230/400 and also wired in delta which due to the different winding ratings will have seen up to 400v depending on speed set across a 230v set up hence burn-out express!

 

[Tiny Spark]

No the originals were rated at 400 star and 700 delta.
The replacements were rated at 400 delta and 700 star.

So basically they have not seen enough voltage.

 

[Darkwood]

No the originals were rated at 400 star and 700 delta.
The replacements were rated at 400 delta and 700 star.

So basically they have not seen enough voltage.

I would be checking things again i think you may be mistaken .... if you have a duel voltage motor say 230/400 the winding itself is rated at 230v...so in delta the 230v exists across 1 winding but when connected in star you have 2 winding in series with the supply so you are able to connect a high voltage.

The Star connection of a standard duel voltage motor is the higher voltage rating of the 2 voltages and the Delta is the lower

230 delta / 400 star
400 delta / 690 star

 

[Tiny Spark]

Well, I never took a piki of the old motors plate but this is the new motors plate sorry about crap quality its dark in them thar units LOL):

http://i676.photobucket.com/albums/...8D34F053-524-0000007BB0ECC553_zps27622a2b.jpg

These were wired in Star.

 

[Darkwood]

Well, I never took a piki of the old motors plate but this is the new motors plate sorry about crap quality its dark in them thar units LOL):

http://i676.photobucket.com/albums/...8D34F053-524-0000007BB0ECC553_zps27622a2b.jpg

These were wired in Star.

Well this motor should be connected in Delta 2nd row down 400v 50hz is your supply.

 

[Tiny Spark]

Well this motor should be connected in Delta 2nd row down 400v 50hz is your supply.

Yup.

I can only hazard a guess that these were swapped "like for like" and only on the basis of finding a really old motor in one of the old units that was rated at 400v star (possibly it was lower voltage delta but i thought it was higher, But wasnt really paying attention to anything other than the 400v bit lol)
The original motors were scrapped a few weeks back so I have no way of being able to confirm or deny this theory.

But at the end of the day atleast I know what the problem was now, Or atleast part of it!

 

[Darkwood]

Yup.

I can only hazard a guess that these were swapped "like for like" and only on the basis of finding a really old motor in one of the old units that was rated at 400v star (possibly it was lower voltage delta but i thought it was higher, But wasnt really paying attention to anything other than the 400v bit lol)
The original motors were scrapped a few weeks back so I have no way of being able to confirm or deny this theory.

But at the end of the day atleast I know what the problem was now, Or atleast part of it!

Crucial part of electrical engineering is paying attention it saves time money and confusion it my be the case the star and delta symbols are at either side of the 400v but one relates to the other voltage ...its crucial you read and understand the plates .... read up and star delta connections and voltage rating also read up on theory of star delta starting this should give you insight to why you are connecting the motors the way you are .... Parrot fashion work ethics is not for the Engineering scene you need to understand why you are connecting the way you are and the consequences of incorrect connections you can't learn anything following advice and reading a motor plate you need to be in a position to understand why its the way it is.

 

[Tiny Spark]

Crucial part of electrical engineering is paying attention it saves time money and confusion it my be the case the star and delta symbols are at either side of the 400v but one relates to the other voltage ...its crucial you read and understand the plates .... read up and star delta connections and voltage rating also read up on theory of star delta starting this should give you insight to why you are connecting the motors the way you are .... Parrot fashion work ethics is not for the Engineering scene you need to understand why you are connecting the way you are and the consequences of incorrect connections you can't learn anything following advice and reading a motor plate you need to be in a position to understand why its the way it is.

Well although i agree with you that its important to pay attention (As this wrongly wired motor proves) some times its easier said than done.
At the end of the day me investigating this issue was not a high priority (as I said up to contractors to sort out) And it was something I wanted to do for my own peace of mind more than anything so I didnt want to get bogged down with what voltages a motor which is running fine would be expecting if it was wired wrongly, Only that it was wired correctly and running
In the case of the motor in question it was wired in star and the rating plate said 400v star.

As I said before I can only makes guesses as to what the original motor was based on the other motors knocking around the site as I was not present when they were changed nor do I have access to them.

 

[Darkwood]

That said then you've had an insight to the basics of motors and trust me after 20yrs im still learning as i discover old technology and learn new... its never ending but its something to think about if your interested in the area of Electrical work.... there is a mass of old retiring Electrical Engineers out there with no-one to fill their shoes as their is a black hole in the market due to dumbing down of the industry and everyone only able to do domestic out of college...

I just be head hunted from Ireland to a firm to help them design a control .... i don't advertise in any form its all word of mouth and unless the project appeals to my interest i usually turn these down as i try stick within 50mile radius but im getting more and more call further afield and its clear from conversations that many are retiring

 

[Tiny Spark]

Yup, Every day is a school day.

Unfortunately for me I went from being the learner to the learned fairly fast.
Well I say fairly, More like very!
Recession has much to answer for including the redundancy of my mentors which left me holding the reigns so to speak (not sure how that happened exactly)
So instead of me having people to ask questions to I now have people asking me which is all well and good until I or they come across something which I know nothing about or have a limited knowledge of!
Sadly this happens more often than I would like as its a large factory with a very wide range of plant and services. Obviously its not possible for me to learn and know everything but I do my best with what I have lol.
That being said I have only ever known industrial work and would feel uncomfortable and out of place in a domestic situation!

But when I get stuck I am thankful for experienced people like yourself and friends to give me a shove in the right direction LOL