3phase compressor.

[Pandrone]

Hi a quick brief, i had practical experience (dunno the english word) in school, i had this at a refrigerationcompany. The a/c experiments i did about a year ago or something are burried (some of you may remember the thread ). I understood that it was too much work and money, better buy a new one.

Well well, in the end of my "practice" i asked if i could take some stuff in their container (used, broken things) to learn the wiring and so on. So i got 2 L'unite Hermetique TAH5540E compressors, i know these are quite big and so on. I just want to see if they work so i sent a mail to tecumseh-europe and got a datasheet.

One thing is that i got two pdf-files and they show different wiringdiagrams both :S.

Here's a pic of the both:





There are no neutral going to the compressor, is this some kind of D-connection?

I would ask my teacher at school, but the christmasholiday started today..

/Tomi

[chemi-cool]

Hi Tomi,

There is no neutral in any three phase motor!!

Only in one phase motors,

Don't they teach you electricity ??

Its impossible to practice refrigeration and AC without knowledge of electricity and control circuits.

Chemi

[Pandrone]

Hi,

I'm in upper secondary school right now (second grade out of 3).

Studying electricity right now we are in the middle of 3phase (continuing after christmas).

We are taught of Delta and Y connections, as i have understood it Y connections have a neutral. And Deltas does not. Though we have not had motors yet, that's the next chapter in the 3phase book . (and i do not have it at home )

The thing is that those two wiringpics in my first post are not alike (and they both come from L'unite Hermetique). If you look at them the phases are in a different order.

My english is not that good, so it's kinda hard to explain..

One more thing, in the datasheet i got the resistance on each phase should be 4.4ohm (20c). I checked one of the compressors and got around 4.8ohm at 16c ambient. I guess this falls in the +-10% margin?

[chemi-cool]

Hi Tomi.

Again, there is no neutral in three phase motors. Not in Y or delta.

The order of the phases in hermetic compressors is not important.

But, always, follow manufacturer instructions.

Chemi

[Pandrone]

Okey, so that's why they have labelled the phases differently in those two diagrams .

I think you answered my questions there, thanks very much .

/Tomi

[Peter_1]

Hi Pandrone,

Seeing your age and the kind of posts you make for your age, well....you are going to make it mate.

You're eager to learn and you even wants to learn more than that you have seen in school. You have the drive to understand what your teacher said, you don't erst till you understand the problem.

Very good attitude for a tech.

This is a prove that you wants to learn more and that you ask an opinion to those who are busy whole days with compressors.

Never be afraid or to shy to ask questions here in this forum and as you have noticed, there is always a quick reply.

Perhaps a littel add to Chem's explanation: in the star-point, you see a circle (This is in fact not quit correct for the Unithé Hermétique compressor I think)
This is the internal clixon. As soon the compressor comes to hot, this clixon opens so that no current can flow anymore through the windings. Or in other words, the star-point opens.
This principle is also used by Maneurop.

Why is in my opinion not correct for UH? UH fits 2 external clixons in the starterbox, connected in serie with 2 windings.

[frank]

The order of the phases in hermetic compressors is not important.

Hi Chemi

Are you saying then that a scroll is not a hermetic?

A scroll that runs backwards does not compress

[Pandrone]

Hi again.

I checked the compressor, it has a label in english and german that i think says Internal Overload Protector (the english part is ripped off).

I remember i wondered why L'unite compressors always had that huge starterbox. So these 3phase compressors come with a starterbox too?


Thanks for the words .

/Tomi

[master rinktec]

Okey, so that's why they have labelled the phases differently in those two diagrams .

I think you answered my questions there, thanks very much .

/Tomi

Reverse any two phases on a three phase motor and the motor will run in the opposite direction.

[chemi-cool]

Are you saying then that a scroll is not a hermetic?

A scroll that runs back-wards does not compress

Hi Frank,

Not to confuse young Tomi I should have added that scrolls are an exception as they can compress only in one direction.
Therefore if no no change appear on the gauges and the noise is abnormal, Reverse any two phases.

We tend to call hermetic scroll compressor, a scroll.

They do not come yet in the semi hermetic or open form as reciprocating and screw's.

I hope I passed Frank

Chemi

[RogGoetsch]

We are taught of Delta and Y connections, as i have understood it Y connections have a neutral. And Deltas does not.

Hi, Tomi,

Three-phase Y and Delta transformers are used in the US to step down transmission line high-voltages.

In residential and light commercial buildings, the Y transformer supplies voltages between the middle neutral and any leg of 120v, used for all lighting circuits and small appliances.

Between any two legs of the Y, we get 208v, used for larger single-phase motors. Three-phase motors use all three legs of the Y.

Delta transformers provide 230-240v from each point on the delta. In the middle of one side of the delta, there is a neutral tap which supplies 115-120v between it and either of the two adjacent points.

The point opposite the neutral tap, however, is known as the "stinger leg" because voltage between it and the neutral is about 200v. Knowledgeable electricians mark this leg with orange tape because connecting it in place of one of the other two legs will blow every light or 115v load connected to the circuit!

Good luck.

Rog

[PobodysNerfect]

Hi, Tomi,

Three-phase Y and Delta transformers are used in the US to step down transmission line high-voltages.

In residential and light commercial buildings, the Y transformer supplies voltages between the middle neutral and any leg of 115-120v, used for all lighting circuits and small appliances.

Between any two legs of the Y, we get 230-240v, used for larger single-phase motors. Three-phase motors use all three legs of the Y.

Delta transformers provide 208v from each point on the delta. In the middle of one side of the delta, there is a neutral tap which supplies 115v between it and either of the two adjacent points.

The point opposite the neutral tap, however, is known as the "stinger leg" because voltage between it and the neutral is above 208v. Knowledgeable electricians mark this leg with orange tape because connecting it in place of one of the other two legs will blow every light or 115v motor connected to the circuit!

Good luck.

Rog

Rog, I don't know the "stinger leg" thing so well, but haven't you mixed up the voltages. I mean, the 3 phase Y must be 208 V, which gives 120V phase / neutral, and where you use the midway point for neutral the voltage must be 230 V to give you 115 V.

Anyway, I don't think they use this midway / stinger leg thing in Sweden.

Saludos,

Jan

[Pandrone]

Tested one of the compressors and it worked fine (it started). When i plugged it in it spit out some oil(much more than the smaller compressors i've used) i guess this is normal? But the oil smelt a bit funky, a bit burnt. But i'm going to drain another small compressor that uses mineraloil to check the smell of it .

Thanks again all of you .

[RogGoetsch]

Rog, I don't know the "stinger leg" thing so well, but haven't you mixed up the voltages. I mean, the 3 phase Y must be 208 V, which gives 120V phase / neutral, and where you use the midway point for neutral the voltage must be 230 V to give you 115 V.

Hmmm. Dossat agrees with you, Jan. I called my electrician buddy and he also agrees. It must be a conspiracy!

It's certainly a sure sign of brain decay that I remember this one wrong! My wife always offers to bet me $50.00 when she knows I'm wrong. She won three bets out of three in the first years of our marriage and now all she has to say is "Want to bet $50.00?" and I know I'm toast.

Rog

[botrous]

Hi Tomy how are you ?
First happu holidays ....
I want to let you be careful for a thing , is that 3 ph motors doesn't have neutral . . .
It just works with 3 phases L1 , L2 , L3 or R, S , T as it is called .
When connecting the 3 pahses to the compressors terminals be aware that the compressor may rotate in reverse which may cause the compressor to burn ....
The sound of a compressor turning in reverse is loud and annormal comparing to one which turns normally , in this case just switch the power off and remove 2 phases from the compressors terminal and switch between them . example : Red wire in position 1 , blue wire in position 2 , and brown wire in position 3 , all that you have to do to change the rotation of the motor is to put the red wire in position 2 and the blue wire in position 1.

Regards / Pierre

[Pandrone]

Hi, got hold of another compressor, an maneurop MTZ028 i think it was labelled..

Anyway, i wired it the same way as the L'unite and it started, i put my finger on the suction but it didn't seem to pull any vacuum, but the discharge blows though. I don't know much about these "big" things, but i guess it should "pull" my finger?

Anyways the motor works, checked the resistance at each phase and they were ca: 7.10ohm and according to the datasheet it should be 7.11ohm at 25c.

Here's a video when i started it, do they sound like this normally?

Link

/ Tomi