Thread: 3ph versus 1ph . cyclone v bag filter

The difference between single and three phase motors is that for the same power rating, the 3 phase unit draws less current from each of the three supply phases. The general limit for a 10A single phase circuit is around 2 HP, or 3HP for dedicated 15A circuits.

Something like a dusty is only usefull when used in conjunction with other gear, again typically in the multi HP range, so you need a lot of circuits to operate dedicated gear.

Three phase motors have better starting torque than equivalent single phase motors, and don't use dedicated start windings, switches, and capacitors which are the primary cause of motor problems with single phase units. However it is advisable to use a 3 phase starter and phase loss protection with 3 phase motors, as their failing is burning windings when starting or running with unbalanced supply.

Whether to go three phase or not is often a question of finances, as you need to get the power to the shed. A short branch from a three phase connected home is possibly viable, but a long haul from a roadside pole or underground supply point can be very expensive. This additional expense can sometimes be partially offset by being able to buy used industrial machinery at reasonable prices (compared to new single phase equivalents), but if the supply system costs say $10K, then you need to save a lot to cover the cost.

On the other hand if the shed is near a house supplied with single phase power, and existing usage approaches the supply rating, finding the capacity to service a number of dedicated 15A single phase circuits might mean that the supply authority requires an upgrade to 3 phase supply anyway.

Therefore it is not an easy question to answer definitely.

Originally Posted by gingerbeer86

First thing I am looking at is DE. I notice that carba-tec has two units of the same flow and same power (3hp) , one is 3 phase the other 1 phase. They have the same flow rates, same price etc so apart from potentially the durability the motor, what would drive a choice of one versus the other? These are the CT003 models.

I have the single 3HP Carbatech phase DC - just after I used it I wondered if the 3 Phase might have been quieter. Most of the noise is no doubt from the impeller but even small gains in noise control are worth having

Carbatec also sell a cyclone which has a 1 micron filter versus the 5 micron in the bag unit, but at over double the price. Anyone see value in a cyclone and the better filtration.

The difference in price between the 1 filter and a 5 micron bag is because the 1 micron filter has a much greater surface area that the 5 micron bag so it needs to be cleaned more often than the 1 micron filter to keep these machines operating optimally.

BTW: If you are planing to vent a cyclone or a DC outside you don't need a fine filter, both 5 and 1 micron particles are invisible so unless you plan to thickness 5 days a week you won't see anything in the air.
Super fine filters are only really necessary for users who cannot vent their cyclone/DC outside.

I am considering putting the dusty in a cabinet with a large louvered vent (450*900) to the outside. For both noise and dust rentry benefits, anyone tried something like that?

A couple of members have done this and they indicate that this approach is worth doing. I also plan to do this and my approach will be the same as that I have used for locating a compressor outside the shed described here.
I'm looking a using 35 or 40 mm tick spotty planks clad with foam on the inside and colorbond to match the shed on the outside.
I will be removing the Frame and mounting the motor/impeller and housing on a pair of steel arms fixed to the side of the shed.

BTW Louvered vents won't stop much noise at all. What is needed is a set of baffles to allow for a long indirect airway that has a wide enough cross section with low air resistance to cope with the high air volumes involved. I can mock up a plan of what I will be doing if you like.
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Originally Posted by malb

The difference between single and three phase motors is that for the same power rating, the 3 phase unit draws less current from each of the three supply phases. The general limit for a 10A single phase circuit is around 2 HP, or 3HP for dedicated 15A circuits.

My Carbatec 3HP single phase unit is wired to fit a 10A plug. I checked the current and it is around 9.6A at max airflow and as expected the current goes down with reduced airflow.

High starting torque is not a requirement for dust extractors but one BIG advantage is that 3Ph motors can be hooked up to a VSD and the motor can then be run at higher frequency/speed. The company that makes these units in Taiwain will not be making two different impellers for 50 and 60 Hz - their construction will have to cope with the higher frequency/speed so this would bring it up to their original design spec. Althouhg it will void your warrantee, these DCs are so well made so that they could probably even operate at 65 or 70Hz. The improvement in air flow from this change in air speed is VERY significant and would be well worth having.

Originally Posted by malb

However it is advisable to use a 3 phase starter and phase loss protection with 3 phase motors, as their failing is burning windings when starting or running with unbalanced supply.

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Mal, phase loss protection...Is this for complete loss of one phase (running on 2 phases) (not good) or a partial loss of voltage on one phase? I'd imagine there'd be an allowable tolerance?


Pete

Originally Posted by BobL

My Carbatec 3HP single phase unit is wired to fit a 10A plug. I checked the current and it is around 9.6A at max airflow and as expected the current goes down with reduced airflow.

High starting torque is not a requirement for dust extractors but one BIG advantage is that 3Ph motors can be hooked up to a VSD and the motor can then be run at higher frequency/speed. The company that makes these units in Taiwain will not be making two different impellers for 50 and 60 Hz - their construction will have to cope with the higher frequency/speed so this would bring it up to their original design spec. Althouhg it will void your warrantee, these DCs are so well made so that they could probably even operate at 65 or 70Hz. The improvement in air flow from this change in air speed is VERY significant and would be well worth having.

Bob What sort of improvment would be typical with a speed increase given the typical 1/2/3/4hp system? Would this improvment be a function of the fan and where it is operating at in terms of pressure and flow in a given system? I am interested for my own system.

Pete

Originally Posted by pjt

Bob What sort of improvment would be typical with a speed increase given the typical 1/2/3/4hp system? Would this improvment be a function of the fan and where it is operating at in terms of pressure and flow in a given system? I am interested for my own system.

Pete

Provided the motor can fully wind up the impeller, increasing the frequency from 50 to 60 Hz provides an 20% increase in RPM and will produce an 20% increase in maximum flow. However, actual flow rates can differ by considerably more than 20%.

The maximum pressure increase depends on how well the impeller is designed/made and how susceptible it is to leaks. In general the pressure increases with the square of the relative change in frequency. Assuming the impellor is well made, there should be a close to 44% increase in pressure in going from 50 to 60 Hz !! In practice it will be less than this.

Lets work with the ideal case of a 44% increase in pressure. The flow rates I quote for a given ducting diam and pressure differential come from a chart I posted a while back but I cannot seem to find it anywhere. For my pressure units I will use "inches of water pressure" abbreviated as "H2O

Consider a 50 Hz DC that can generate a maximum of 10 "H2O, but the DC system uses up 6 "H2O to overcome bag, junction, ducting and machine port resistance then that leaves only 4 "H2O to remove dust. In 6" diam smooth wall ducting 4 "H2O will move 800 CFM (this ie below the Bill Pentz spec). This is typical of just about every 2 and 3 HP system I have seen. Going from 50 to 60 Hz should generate an additional 44% or 4.4 "H2O of water pressure over the original 10 "H2O this means that instead of only using 4 "H2O to move the air 8.4 "H2O is now available - this should move ~1300 cfm which is now well above the BP criteria. This is really worth having.

If the DC is so clogged it has only 2 "H2O available to pull air this will result in a flow of 540 CFM thru 6" diam pipe. Adding an extra 4.4 "H2O now equals a total of 6.4 "H2O which should result in a flow rate of nearly 1000 CFM which is a massive improvement in flow rate.

Note this assumes 6" diam pipe all the way to the machine. In practice machine ports are too small and seriously increase the pressure requiriments to pull air through them. In practice the improvements won't be this good but it does show you the role of pressure in DC systems

Now lets go to 70 Hz ! and things will really Hum!!!!!

[EDIT] I just realized that there are some serious power ramifications that could prevent most 3 Phase motors from operating in this way. Unlike a lathe or a drill press where increasing the Hz increases the free running speed and the current drawn by the motor still depends largely on applied load, on a DC or any electrical pump the power drawn is dependent on the cube of the change in speed. So a 50 to 60 Hz change means the motor will draw ~60% more power. How many 50 Hz 3 phase motors out there that can handle this would be the next question to ask.

[EDIT2] corrected some pressure values from "psi" to "inches of water pressure" Abbreviated as "H2O

Yes, The power = speed cubed is the killer, I know in my system I have a little bit of spare motor capacity,(3kw) I could use up some of this spare with a larger dia. fan wheel and a redesign of the inlet() mine is 300mm with backward facing curved blades but wide so I do get a good flow but my says I am down on pressure but I need to measure the flow which I haven't done (no measuring gear) I have 200mm pipe for the main runs and 100mm dwv? (sewer pipe) which is closer to 115mm inside and then short bits of 100mm and 125mm flexable, room for improvement there as well but not too bad, so for my system I probably could improve flow and pressure with a VSD.
I am thinking that to make the most of having a VSD would be to have an amp meter showing current draw and then set VSD accordingly, this could then be adjusted for each machine, blast gates open/closed, leaks or if ducting mods are made (longer/shorter runs) bags clogging up, or any number of inefficiencies, although we should always strive to make systems as efficient as possible.

ON a completely different note Bob, you would be familliar with Magnehelic? guages wouldn't you? for measuring pressures


Pete

PS apologies if I am hijacking GB's thread

Originally Posted by pjt

Yes, The power = speed cubed is the killer, I know in my system I have a little bit of spare motor capacity,(3kw) I could use up some of this spare with a larger dia. fan wheel and a redesign of the inlet() mine is 300mm with backward facing curved blades but wide so I do get a good flow but my says I am down on pressure but I need to measure the flow which I haven't done (no measuring gear)

From Bill Pentz site "A 12" airfoil driven by only a 2 hp motor is rated at 1200 CFM at 7"sp. It produces 1700 CFM at 4", 2000 CFM at 2", and 2250 CFM at 0". The DC vendors would wrongly advertise these units as 2 hp and 2250 CFM at 7" static pressure."
This of course also assumes a 60 Hz power supply so the impeller spins at 3600 rpm.

A 3 kW = 4HP motor could easily drive a 14" impeller which would be a better fix than a VSD on 60 Hz with a 12" impeller

It is very easy to make your own pressure measuring device (manometer). Just get some 6 mm ID clear flexible pvc tubing and bend it into a narrow U shape with the sides of the U at least 20" long. Fix it to something like a bit of chipboard or MDF so that it can stand up vertically. On one side of the U connect a metre of so of cheap tubing that will allow you to connect to various take off points in your system the main one being just above the impeller. Fill the U tube with a mix of water and food colouring to a height of ~10 inches and place a distance scale in the middle of the U so you can measure the difference between the levels which is a direct measure of "H2O. If you want to be fancy you can place Pascal (Pa) scale alongside so you can relates these to the usual charts that a floating around on the net.

I have 200mm pipe for the main runs and 100mm dwv? (sewer pipe) which is closer to 115mm inside and then short bits of 100mm and 125mm flexable, room for improvement there as well but not too bad, so for my system I probably could improve flow and pressure with a VSD.

Your weakest link by far is the 100 mm pipe. For example even if you have 6 "H2O the most air you can drive through a 100 mm diam pipe is 320 CFM, while 8 "H2O of pressure will only push 400 cfm and 10 "H2O will push 450 CFM. In contrast 150 mm diam can carry ~1000 cfm at 6 "H2O 1500 cfm at 8 "H2O" and about 2000 at 10 "H2O. Using 100 mm pipe on any 2 or 3 HP system is like buying a 6 cylinder car and disconnecting 2 spark plugs.

Unless you have done something about them, next will be the machine ports. You would gain immediately by replacing the 4" with 6" diam sewer pipe and in the first instance making a adapters at the end of the 6" diam line that adapts the 6" diam line to 2 or 3 x 4" ports and taking the flexy from there. Not many machines have 2 or 3 ports so even if you can only connect 1 up to a machine the other ports should just be left open so there is enough air volume being moved so the dust doesn't settle in the 6" and 8" diam pipe. Better still would be to add 4" flexy to all 3 ports and attach them as close as possible to the dust making area on the machine and they will efficientlt scavenge the fine dust that will otherwise escape from the machine. Bill Pent'z site has a useful section on how to do this. (Bill's Cyclone & Dust Collection Research - Ducting). Ultimately moddify machinery to take 6" diam flexy is the way to go.

I am thinking that to make the most of having a VSD would be to have an amp meter showing current draw and then set VSD accordingly, this could then be adjusted for each machine, blast gates open/closed, leaks or if ducting mods are made (longer/shorter runs) bags clogging up, or any number of inefficiencies, although we should always strive to make systems as efficient as possible.

That would be an excellent way of tackling it.

PS apologies if I am hijacking GB's thread

Me too.

Thanks Malb and Bobl, Sounds like 3 phase is the go. Being new construction, i have the luxury of starting with a clean sheet. I have bought a 3 phase line to the shed. There is already a 100amp 3phase supply to the house (apparently for a 25kw aircon, we have just bought the house). I am also putting 4 * 15amp points and 2 * 10 amp points around the shed.

Any thread on DE seems to mutate into a techo feast, such much for the simple task of moving dust. I have read the pdf from Bill Pentz on DE and will be using a 150mm duct, how it mates to the table saw will depend on which saw I get and if it is possible to enlarge the bottom duct. Plus I want to get a well ducted guard. If there is a well designed, well ducted guard that has good visibility, then that eliminates at least part of the temptation to operate without a guard.

Sounds like 1 micron versus 5 is a bit of a mute point if I enclose the unit and vent to the outside. I was hoping to avoid the use of baffles, so might try with out and see how it goes. The neighbours on that side are a long way away, so should be ok there.

Always make sure when you are drawing air from a cabinet saw or router cabinet that you supply the same flow of make up air. I created a 150mm opening for the DE in my TS and left the original 100mm duct open to the air. This seems to work very well as there is high speed air movement through the cabinet and the air gap under the table go some way to making up the rest if not all the way. As for a blade guard and visibility I think that LEDS could be imbedded in a perspex guard that had a 100mm line coming off it. The LEDS should overcome the visibility problems nicely I hope.

Originally Posted by Mini

Always make sure when you are drawing air from a cabinet saw or router cabinet that you supply the same flow of make up air. I created a 150mm opening for the DE in my TS and left the original 100mm duct open to the air.

That's a very good way to go about it. If making the opening larger to suit the 150 mm pipe is beyond a users ability to organize then hooking up a 1 x 100 mm flexy to a standard 100 mm machine port, and place another 100 mm piece of flexy as close as possible to the machine where the dust is being made is a reasonable alternative.

Some systems I have seen and heard about use a 150 mm main line and a 1 x 100 mm flexy to the standard 100 mm machine port, and a make up air port somewhere else in the shed, or open up a blast gate to another machine. While this will maintain air flow in the 150 mm pipe and reduced the possibility of dust dropping out of that line it also will create an additional low pressure area elsewhere in the shed which will help spread fine dust through out the shed.

. As for a blade guard and visibility I think that LEDS could be imbedded in a perspex guard that had a 100mm line coming off it. The LEDS should overcome the visibility problems nicely I hope.

excellent Idea - I might just be using that one

Originally Posted by gingerbeer86

Thanks Malb and Bobl, Sounds like 3 phase is the go. Being new construction, i have the luxury of starting with a clean sheet. I have bought a 3 phase line to the shed. There is already a 100amp 3phase supply to the house (apparently for a 25kw aircon, we have just bought the house). I am also putting 4 * 15amp points and 2 * 10 amp points around the shed.

I don't know how big your shed is but that does not sound like enough 10 A points to me.

Any thread on DE seems to mutate into a techo feast, such much for the simple task of moving dust.

I agree - but as everyones shed and shed layout is usually different it is not always easy to make simple decisions. 25 years ago when I first started on reading up about moving air around and then designing and building air handling systems from scratch I also thought - this can't be too hard - but it was a lot harder than I thought it would be and even now I reckon I have a lot to learn.

Sounds like 1 micron versus 5 is a bit of a mute point if I enclose the unit and vent to the outside. I was hoping to avoid the use of baffles, so might try with out and see how it goes. The neighbours on that side are a long way away, so should be ok there.

That sounds eminently sensible.

I thought I was some way from building my DC enclosure (I just cleared the space today) and was looking at processing some of the excess large Spotty slabs I milled in 2008 for the main bulk of the housing. If I was to go this way it would take me some time to mill and dimension the timber, but I checked my stash and see I have 3 sheets of 32 mm melamine internal wall panel that has been sitting there doing nothing for 3 years that might be sufficient to do most of the enclosure with this stuff. I picked the melamine up for nothing from a builder who was doing a major office reno in the city so it owes me nothing. Anyway if I get some time I will start on it next weekend. This means I will be able to test my baffle system out relatively sooner than I thought.

I am in the middle of building a sound reducing booth for my cyclone. Two sheets of 19mm MDF with a 70mm cavity I stuffed full of flattened cardboard boxes for each wall and the roof. I will line it with old carpet and then see how much it has reduced the noise. The cardboard boxes were an off the wall idea I had and they were free but I have no scientific basis to judge whether it is a good idea or not though I spoke to a fair few people and they all seemed to think it should work. One thing I am not doing is a before and after test so will live with the result.

Originally Posted by Mini

I am in the middle of building a sound reducing booth for my cyclone. Two sheets of 19mm MDF with a 70mm cavity I stuffed full of flattened cardboard boxes for each wall and the roof. I will line it with old carpet and then see how much it has reduced the noise. The cardboard boxes were an off the wall idea I had and they were free but I have no scientific basis to judge whether it is a good idea or not though I spoke to a fair few people and they all seemed to think it should work. One thing I am not doing is a before and after test so will live with the result.

Sounds like a very interesting approach and scientifically has quite a bit going for it.

If you are building with a cavity, you might want to consider metal studs because they provide about a small improvement over wooden studs.

In terms of filling the cavity, rock wool insulation would have been slightly better than compressed cardboard but unless you had spare rock wool laying around you'd have to buy a whole pack and using compressed cardboard is a lot cheaper and will be nearly as effective.

I presume the enclosure is under cover or inside the shed ?

Are you just enclosing just the cyclone? If so some noise will escape from the air exit.

Anyway it sounds like an interesting project - I'l like to see some photos when it's done.