2300v motor efficiency 6

[Lostinquebec]

I run a 2300v compressor 24/7 year round and it pulls 110A and blows half of the air out the wall.
I can make some adjustments and get it easily down to 97A.
Can anyone help me with the kind of power and financial savings i'd be looking at?
The Company doesn't seem interested but I feel this could be a significant savings


Lostinquebec

 

[jraef]

How is it that you are going to reduce the running current by “making adjustments”? Adjustments to what?

Here’s where I’m going with that. If you lower the current by lowering the load on the motor, but at the same time increase the running time to deliver the same net amount of air over a given time frame, you don’t save energy. Current is not energy, current is a component of power, and power is a component of energy, along with time.

In compressed air systems, the number one way to save energy is to focus your attention on leaks.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[edison123]

What does 'blows half of the air out the wall' mean? Leaks?

Muthu

http://www.edison.co.in

 

[Lostinquebec]

What I mean is I can lower the minimum power setting safely to at least 96 Amps while staying away from the surge curve. The air blowing out the wall is due to the min power setting being at 110 Amps and so the blowoff valve opens to keep that setting and blows it out the wall.

Lostinquebec

 

[waross]

We need some answers before we can help you, but there may be significant savings to be had.
HP?
RPM?
Air Pressure?
What is the air used for?
Is this a synchronous motor used for Power Factor Correction as well as driving a compressor?
It is very unusual for a large compressor to be controlled by minimum load. Very unusual.
Does your compressor have mechanical issues if it is not loaded?
I suspect that your motor may be correcting the Power Factor and by reducing the current you may be increasing the Power Factor penalties.
It is so unusual to control a compressor by the minimum current that I strongly suspect that the motor is also correcting the PF.
But, wasting air costs money. It is not cheap to run a 2300 Volt air compressor.

I will assume that the motor is being overexcited for power factor correction and the actual motor current without correction is about 90 Amps.
I'll use 88% efficiency and we get a figure of 318.7 kw. at $0.10 per KWHr that is about $32 per hour to run that compressor.
That's $23,000 per month.
You don't have to be wasting much air to be wasting a lot of money.
If you are able to provide a scan of one of the plant's power bills 9with the identity of the company blanked out) it may help us.
I have use a figure of $0.10 per KWHr, but the cost energy may not be the only cost.
I get energy fir about $0.06 per KWHr but transmission and distribution charges about double that.
The big issue is not the possible reduction of the current, but the waste energy represented by the lost air blown out the wall. That may be big dollars being blown away.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Lostinquebec]

Induction Motor 600hp,3565 rpm,118 psi,0.993 - 0.998 power factor
My coworkers seem to be under the belief that it needs to blowoff at all times. Which at times can be half of the air produced, so say 500cfm out the wall.


Lostinquebec

 

[Lostinquebec]

They also are concerned about the vibrations, which do not change really and are well within parameters, like the highest being 0.80 mils

Lostinquebec

 

[Lostinquebec]

It actually all started by trying to get the blowoff valve closed.Then they rebuilt one so ots tight now and blows off even more!

Lostinquebec

 

[Lostinquebec]

Even the compressor contractor made a big deal and put out a note that this machine must blow off at all times?

Lostinquebec

 

[waross]

What kind of compressor?
Can you share the make and model?

Even the compressor contractor made a big deal and put out a note that this machine must blow off at all times?

Maybe he doesn't know how to connect and wire an unloaded.
Something is not right here.
A machine that size should not be wasting compressed air and expensive energy that way.
Was this a new compressor when it was installed or was it an "experienced" machine?
I may be about to learn something new here, but maybe not.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Lostinquebec]

It's an elliott 3 stage centrifugal P/P Plus. Honestly I feel like either I'm missing something here, or someone doesn't understand their machine

Lostinquebec

 

[Lostinquebec]

Model 220 DA3

Lostinquebec

 

[Lostinquebec]

More nfo

Lostinquebec

 

[waross]

I am starting to believe that there may be machanical issues involved.
To that end I have posted a question and a link in the Gas Compression Engineering Forum.

Centrifugal Compressor in Continuous Blowdown.
thread1036-446163


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Lostinquebec]

I don't think so, I feel like its just been ranlike this so everybody panicks if you touch it. I have done many tests with the reduced power setting and had no adverse effects.I was just wondering about the savings.
The contractor is out to lunch

Lostinquebec

 

[waross]

I am wondering if there is some reason that they don't want to use suction throttling to control the capacity. Possibly to avoid a negative internal pressure from drawing in lube oil?
I don't know.
That machine is too expensive for me to start guessing out of my area of expertise.
I hope the gas compression group can give us some input on the mechanical factors.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Obvious questions are:
[ul]
[li]What type of compressor - screw, turbine, reciprocating?[/li]
[li]Do you ever require the full output capability of the machine?[/li]
[/ul]

With the above information some options may be ruled in or ruled out.

To quantify your potential energy savings why not buy or hire a power meter? Your switchboard presumably has at least an ammeter CT on the compressor circuit and there should be a busbar VT somewhere on the board so you have the signals you require to get a true power measurement at whatever operating point your compressor is working at. If you don't have a busbar VT then you can use the control power transformer in the starter panel: the accuracy of the measurement will be considerably worse, but it sounds like it's a comparison you're looking for rather than fiscal-class measurements.

 

[Lostinquebec]

It's a centrifugal (turbine) type. Full capacity is rarely needed as we have less demand than before. I actually was looking for financial savings to try to prove my case.

Lostinquebec

 

[BrianPetersen]

Turbomachinery doesn't like operating at flow rates below design values (and you alluded to this with the discussion of the surge limit), whether by intake throttling or reducing operating RPM. A unit that big also isn't going to like starting and stopping. If your demand is much less than what the machine is designed to provide, it follows that you have a compressor which is too big for the application. Right sizing is extremely important for these.

There is no easy fix short of replacing the unit. Minor fiddling here and there could save a few percent (as you evidently have shown) but if it is throwing away half the air that it's compressing, the right solution is to replace the entire unit with one half the size ... and preferably with one that's designed to allow variable output in some fashion.

Back of notepad calculations with a little bit of guesswork suggests that it's costing about $400,000 per year in electricity to operate this unit. If it's too big by a factor of two, there is money on the table for replacing it.

 

[edison123]

The compressor seems oversized for the present requirement. Is there going to be additional requirement of air in future? If not, compare the cost of new right sized compressor vs present cost of energy for running this wasteful compressor. The motor efficiencies are pretty much fixed for the entire load range and you cannot do much to change them. Running cost of this 600 HP motor (with whatever efficiency you are planning on improving, which I really doubt) with current wasteful compressor vs the running cost of right sized compressor with the same motor or even a new lower HP motor. Which do you think is 'efficient' in the long run?

Muthu

http://www.edison.co.in