Dart threadwheel skimmer build

Thats why I asked what the VA and PF were though. The wattage of 160 is okay, but only if that wattage is achieved while not causing the pump to be severely out of phase... the pump could be sucking more VA than stock... more juice, and therefore more heat.
 
hann,
can you give us better ideas of how to test these and what meters to use. everyone who has ever converted a pump for a different use can benifit from that information.
 
You should have PF on your Kill-A-Watt... you have to press down the watt button twice I think. What these two numbers give you an idea of is how out of phase the motor might be with the wall current. The VA is the true power that the pump is consuming, regardless of how out of phase the pump may be. The power factor is an indication as well. You want the VA to be as close to the wattage as possible, and the PF to be as close to stock as possible.

That VA reading suggests that the true power being consumed by the pump is higher than normal, as when its running at the speed it should be, the VA should be the same (or very close) to the actual wattage.

At least, this is my understanding of it. I think there is someone else here who can explain it better than I can...
 
The PF is not really worth getting into. This keeps coming up like it is sime kind of "control" or changeable operating parameter. It is way more complicated than that. Even saying "well at no load the kill-a-watt says the PF is .xx and at full output the PF is at .yy so we should shoout for .xy" is silly.

Remember that you have 2 HOT legs in your residential service. You get billed for the summation of the PF on both of those legs (not to mention what your neighbors house may be running). Remember you don't get your own transformer tap, you share it with several people on your block. You share a common neutral with many other people. This means that your meter (in theory) is affected by their utilization equipment. The power company WANTS it this way (undersized neutral) so that you get whacked for power factor instead of them.

SO let me stress this again. Motor load in reality has LITTLE to do with SYSTEM power factor (what you meter sees as the total load on it). Even if motor load had some effect, correcting for it is a totaly different story.

Motors are designed with torque and load in mind, not PF. In LARGE facilities with a LOT of LARGE motors, you may find BANKS of PF correction capacitors.... we certainly do not have motors that large in that kind of numbers :)

When you guys start making skimmers outof 100HP motors, then we can talk about PF correction and what it may save us.

I know this is not really the answer you guys were looking for... but the point is that the topic is kind of useless to even bring up.

Until you REALLY UNDERSTAND power generation and TRUE POWER, APPARENT POWER and REACTIVE POWER, you have no chance of grasping POWER FACTOR. This means a pretty in depth understanding of phase, phase angle, current and voltage lag, etc.

The wiki entry that ChemE provided is a good start... here are a few websites that provide a bit of PF information pertaining to induction motors.

http://www.reliance.com/mtr/pwrfcrmn.htm
http://www.usmotors.com/products/ProFacts/1-115.htm
 
But Bean, were not talkin about how it influences our grid, utility bills, etc... were talking something more downstream here. The PF is a good indication how much the pump is spinning out of sync with the current...its efficiency. This is also shown with the VA. For instance, I know I have mentioned before how PF is used to calculate pump efficiency, and while I agree that this has little to no impact on the grid of our homes, thats not what we are looking at here.

This link has another way of stating the efficiency equasion:
http://www.lawrencepumps.com/newsletter/news_v02_i5_may05.html

news_may05_pwr_eq.gif

For KW use 1000 instead of 746

As you can see, the PF has a great deal to do with the overall efficnency of the pump. Efficiency being the desired output/ required input. The lower the efficiency, the less work gets done, and then you should start looking at the 1st and maybe 2nd laws of thermaldynamics... the work done by the pump and the heat put out by it are the two major components of this. If the efficiency goes down because of a low power factor, that can mean more wattage wasted on heat... which means less efficiency in the windings due to the more heat... and so you need more input to get less output. The only way I see around this is with the use of a digital pump or DC pump.

I actually had someone else in mind who knows a great deal more about pumps here.
 
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The point is that you are reading WAY to much into the PF reading that the kill-a-watt is giving you. Regarding "how much it is slipping behind the phase". There is a lot more to than power factor. My point was that the relationship is so complex that it is really not worth making a fuss about. It follows that a "reading" from a device like a kill-a-watt is somewhat meaningless.

You say you are not concerned about the net effect on the grid or power system, but hte overall efficiency of the pump!!... That would mean you do not understand real and reactive power. The efficiency is a product of the two!

Just watching the KWh reading of the kill-a-watt is enough to get you closer than you ever want with regards to BEP (best operating point). Again, BEP and PF are moving targets with regards to the motor. You can't dial them in without knowing what the overall system PF is... the idea is to try and get PF to UNITY (and there will be BEP as well). Once again, UNITY is somewhat imaginary and has MANY influences internal to the pump and external to the power system.

I am not trying to be rude here.. but hahn please lets not start stating laws of thermodynamics and all that nonsense. None of it matters. You have no way of correcting power factor with regards to a pump this small. It is a moving target and not worth the effort.

A DC pump needs a rectifier and likely a hefty transformer to step the voltage. There is a substantial loss there in terms of heat and ripple. Not only that but the rectifier itself poses a somewhat complex load to the grid....

If we were talking about an industrial complex with a floor full of 100HP conveyor drives and pumps..

Yes, that is the basic equation for brake horsepower.... seen it and used it 100 times. Hahn, remember in a past life I spent 15 years working in undeground coal mines. We power things with 580/575 and 2100 volts. We use motors that are rated in hundreds to thousands of horsepower. We use DC drives in some cases, not because they are efficient, but because they are very easy to speed control. We are talking about facilities that pay $10,000 a day for electricity. In that case PF becomes an issue. The answer is not to correct the motors for PF, but to put large banks of capacitors at the substation... OR to simply work out a deal with the power company due to the size of the operation.

Don't get me wrong. Power generation and real/reactive/imaginary (what ever other term you like) topics are VERY interesting. It is just that in this case it is about as usefull as talking about the moleculare makeup of the pump housing.

Bean
 
Just a side note: you said "A DC pump needs a rectifier and likely a hefty transformer to step the voltage. There is a substantial loss there in terms of heat and ripple. Not only that but the rectifier itself poses a somewhat complex load to the grid...."

This isnt so true any more. Solid state electronics are able to convert the power very efficiently unlike old systems with capacitors and inductors. Maybe not on the large industrial scale, but as far as smaller pumps are concerned... its the basic idea behind the digital pumps.

I dont know if I would consider pump efficiency so much a 'moving target' as you say... I have been able to modify the impeller diameter and thickness before to get as close to the original pump's specs as possible. Thats kind of what Im getting at here...

In the case of this dart, I would suggest trimming the diameter back a little... maybe just a 1/4" or so from the diameter...
 
ok this is getting to the point of splitting hairs, we done need to be splitting. :lol: :lol:

the main topic before we got the hair splitter out was the excess power load on the ao smith motors vs the heavier duty baldor motors. the one thing i got from baldor when talking to there rep was that the baldor motor was spec'ed for a a higher ambient air temp than the ao smith motors are not. that in its self will dissipate heat a lot better because of its efficient design. the problem is that sequence has stopped buying that motor. and they have an agreement with sequence to not sell that motor to anyone other than mdm sequence. so we are in a little bit of a pickle for a little while. there is other alternatives that I will not discuss right now but for now the ao smith dart pumps are the only thing you can get on the market. so to make these lighter duty motors work with out overheating there is a couple of solutions to the problem. first is reducing the flywheel horse power needed to turn the thread wheels. this is easy. just make them smaller in diameter. it make alot of difference in the load just by reducing the wheel by 1/2" in diam. the other way to reduce heat build up is to install a cool collar over the motor housing. this will help in transferring the heat to the outside of the fins so the motor will run cooler and not risk a thermal shutdown.

until there is a better(baldor) motor on the market this will have to do for now. its not the cure its just a band aid for the problem.

ok bean animal and hannimister let me have it. :lol: :lol: :lol:

answers that is. :lol: :lol:
 
hahn.... last time I checked diodes were solid state. You do not need capacitors or inductors if you do not want to filter the ripple caused by the AC sine wave. If you want to filter the ripple, then you need the caps and possibly the inductors. There is no MAGIC to creating DC voltage and it is certainly not something that "new solid state technology" is making more efficient.

I don't care what you call it.... a brushless DC motor, a "digital motor" whatever. You need to take 120VAC and convert it to VDC. This requires a rectifer and a transformer... there is no way around it. No magic, no secrets. What the pumps drive does with the voltage and current is a different story.

I never said that you could not modify a pump to draw less current and produce more bubbles. I AM SAYING that talking about power factor and using it as some kind of gauge or target is useless. If you do not understand why it is a moving target, then you do not understand power factor :)

Let me put this another way. If you could sell "power factor correction" boxes for every small pump on the planet and it was as easy as a cap and coil.... you would be rich beyond belieft. You could sell little weight kits for furnace motors to fine tune the PF, just like balancing a tire... you would be even richer :) Sell the kit with the kill-a-watt a "little black box" for every motor in the house and maybe weights for fan motors and the like. Sell em for $50 bucks and promise energy savings. Don't forget to invite me on a cruise once you start raking in the cash!

Spazz, don't confuse efficiency with build quality. The baldors can run hotter because they use heavier windings and more iron with better glue and insulation. In many cases, they may not be AS efficient, but they do have a heavier duty cycle.

You are correct... (as was hahn) the best thing to do if duty environment or load causes a heating concern is to reduce the diamter of the disc and therefore reduce the drag. Those cool colars are also an alternative.... though I never did order one for my T4 pumps and never got around to casting the ones I designed.

Enjoy guys... I don't have much more to add.
 
"If you do not understand why it is a moving target, then you do not understand power factor :)"

Bean is the only guy I know that undermines your credibility and ends it with a smiley face. lol

I agree 100% Spazz, no argument from me. Cutting the wheel diameter back a little is exactly what I suggested in my last post. It should raise the power factor on the Kill-A-watt as well.
 
ok the hair splitter is tucked away in the closet now for another day. :lolspin:

on a more serous note... if the armature on a motor is bigger than it will also increase the torque of the motor without using a lot more energy. correct???? if this is the case than we might be able to find an alternative motor with a bigger internal size to it, and not increase the wattage draw very much. I understand that the windings may be a little different but if the motor were built a lot like the baldor motors that use to come on the dart pumps than the diam of the wheel can stay the same.

has anyone contacted sequence to see if the 750 series still has the baldor motor on it? if it does than we are still in business. they charge more for the 750 series pumps over the reef flow dart. maybe they still are using that baldor motor on the 750's and not on the darts. this would cure a lot of the problems that come with the cheaper ao smith motors.
 
Spazz there are a LOT of variables... the mass of the iron in the field, the size and number of windings, the shape of the windings (round or flat)... and a half dozen other things contribute to the motors efficiency at a given load.

The baldors are not the only good motors out there, however they are a good standard to judge by. I have never owned one of these pumps... what size frame are the motors and mounting holes? I would imagine they are a standard mount. If this is the case, you can likely find any number of motors to fit. Baldor likely has the same motor in a generic "frame" that is sold to OEM just like they sell to MDM. I doubt (but it is possible) that baldor was building those motors just for MDM. Instead it would more than likely be an off the shelf part.
 
a little off topic but when did they use hubbell motors on sequence darts?i just bought one from a guy i was hoping for the baldor motor,ended up with a hubbell?Any comments on the hubbell motors?
 
OK, so I guess I will cut the diameter a bit on my wheel! Is it going to reduce the amount of air the pump pulls in?
 
<a href=showthread.php?s=&postid=8592892#post8592892 target=_blank>Originally posted</a> by smjtkj
OK, so I guess I will cut the diameter a bit on my wheel! Is it going to reduce the amount of air the pump pulls in?
Click to expand...

it will reduce it a little bit but that is better than having the motor shut down from thermal overload or burn up from getting too hot. bill wann has burnt up 2 of those ao smith motors in the last year. they just cant handle the load placed on it like the baldors can.
 
Spazz, the reason for the price discrepancies in the 750 and the Dart is that Reeflo chose a specific model of the 750(I can't remember off hand which one it was) and they mass produced it to save a little off of manufacturing costs and called it a Dart. This was done to many of the other sequence pumps and they are now "named" pumps...i.e. dart, hammerhead, barracuda, Marlin, etc. Reeflo did this to increase marketability of the pumps and to lower the retail prices. HTH.
 
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