Is a 1.5 HP cyclone enough for my garage shop?

[Allan Speers]

^ Great info, Dave.

Thx.

[Curt Harms]

Ah yes, of course. I meant air speed, not CFM. My bad.




But again, this is what I don't understand. It must be so, but it makes no sense to me:

A 3450 rpm motor runs at 3450 rpm.
How can having no load make it speed up?
If it DOESN'T speed up, and it has no load, how can it possibly pull MORE current?

What am I missing here?

The motor may not be turning 3450 RPM if it's overloaded. I can't see how a motor with no load would draw more current but I think a heavily loaded electric motor's speed will drop a bit below the rated speed before stalling.

[Frank Pratt]

But again, this is what I don't understand. It must be so, but it makes no sense to me:

A 3450 rpm motor runs at 3450 rpm.
How can having no load make it speed up?
If it DOESN'T speed up, and it has no load, how can it possibly pull MORE current?

What am I missing here?

A 3450 RPM motor is a 2 pole motor & has a theoretical no load speed of 3600 RPM. That is, the magnetic field is rotating at 3600 RPM. If the rotor is turning at the same speed, there is no work being done. As soon as the rotor slows below that speed, the magnetic field induces electrical current in the rotor, which sets up a magnetic field that the rotating field created by the winding 'drags' along. The motor is then able to do some work. The more drag on the motor, the slower the rotor turns. That increased the differential speed between the rotor & the magnetic field, which in turn strengthens the rotor field, allowing the motor to do more work

The more load on the rotor, the more work the motor can do, up to the point where the rotor slows to the point where it stalls. Before that point is reached, the motor is in overload & will burn out in short order.

So the short answer is that the 3450 RPM rating is the speed at which the motor runs at full load. With no load, the motor may run at something closer to 3600 RPM.

[Allan Speers]

.... So the short answer is that the 3450 RPM rating is the speed at which the motor runs at full load. With no load, the motor may run at something closer to 3600 RPM.

And again, how does that tiny change in speed, with no load, cause it to overheat?

I still don't get it.

At all.

[Frank Pratt]

And again, how does that tiny change in speed, with no load, cause it to overheat?

I still don't get it.

At all.

Any change in speed is always accompanied by a change in load, whether internal or external to the motor. Load goes up - speed goes down - current goes up. The change in speed, no load to full load, is not that great in an induction motor, unlilke a universal motor (eg. router, vacuum) where the no load speed can be multiples of the full load speed

[John K Jordan]

And again, how does that tiny change in speed, with no load, cause it to overheat?

I still don't get it.

At all.

In the case of a cyclone DC, the amperage is indeed the lowest when the the blast gates are closed and moving almost no air and goes up as the blast gates are open. (I measured it both ways with a clip-on amp meter.) By extrapolation then, it makes sense that running the motor with impeller in an incompletely assembled system, for example, with the bottom of the cyclone cone open, would push even more air and draw even more current.

But I always thought of it in a different way, right or wrong, I don't know: that the motor is doing the least amount of work when the gates are closed because very little air is moving through the impeller. This would put the impeller in a partial vacuum and the reduced air resistance would let the motor do less work. (In a "perfect" vacuum the motor will be doing no work moving air.) An impeller spun with no restriction from ducts or machines would have the most air resistance and work the hardest, drawing more current. I have read of people overheating the motor by testing a cyclone without the ductwork or bin attached.

One could call a company like ClearVue and ask. Or maybe I could ask my friend Joe - he knows everything there is to know about motors and air pressure.

JKJ

[David Kumm]

The speed is related to amp draw only if at the same time the impeller is moving more air and thus working harder. I run my straight blade impeller with a vfd and set the display to measure amperage. I can see how opening gates increases the amperage until the main duct can not support more air. At that point, opening more gates doesn't add cfm or increase amp draw. Watching amps also tells me when the filters are filling up and need to be cleaned. When I want to maximize cfm, I increase the HZ to speed up the impeller until I reach a certain amperage or the rpm rating of the impeller. Impellers are all rated for a max rpm and you don't want to exceed that. A vfd is a do it yourself manual type of Oneida Smart collector. You can adjust speed to compensate for varying duct sizes if the impeller will pull cfm at higher pressures. Dave

[Allan Speers]

I think I finally get it. - It's because the impeller spins in "free air" even if the inlet were completely closed off.
- And motors are designed in the first place to run with a load.

"lightbulb"

--------------

BTW, Jim mentioned way back to make sure I didn't have "Home Despot" quality, 26 g ducting.

I measured mine and it's 21 gauge, including all the drops.

Sweet.
--------------

Also, FWIW:

I plan on cutting a hole in my garage-shop ceiling, and mounting the cyclone high enough that the main duct goes straight into the inlet. This will help optiimize the system in 2 ways:

1: Less resistance at that point.
2: Less turbulance, entering the blower.

I figure that, plus venting outside, plus putting my planer closest to the cyclone, plus the planer being only 12" and having a Shelix head, plus having two air cleaners on the walls, plus always wearing a respirator, and I should be OK.

[Allan Speers]

..... Watching amps also tells me when the filters are filling up and need to be cleaned. When I want to maximize cfm, I increase the HZ to speed up the impeller until I reach a certain amperage or the rpm rating of the impeller..... A vfd is a do it yourself manual type of Oneida Smart collector. You can adjust speed to compensate for varying duct sizes if the impeller will pull cfm at higher pressures. Dave

Dave, you make a very good case for using a 3 ph motor! - Esp the VFD's amps read-out, used to monitor your filter.

Well, I suppose any permanent ammeter would do the same, with a 1 ph motor. That's a great idea.

[Peter Christensen]

To monitor filters a manometer is usually easier especially if you don't have a good electrical background and a history of the DC performance from the git go. Either a Magnehelic type gauge (little spendy) or the simple water in a "U" tube kind. When the pressure differential between the filters and the room are 2" or 3" of water column it's time to clean the filters. So if the clean filter pressure was 1" W.C. and it gets to 3" W.C. then it is cleaning time. The filter manufacturer should be able to advise on how much back pressure constitutes a dirty filter or you can decide for yourself based on performance and looking at the filter.

More to think about eh.

I was poking around the link and they have a kit made just for monitoring filters. Who'd a thunk?

[Allan Speers]

More to think about eh.

No worries, my head exploded long ago!

It can't possibly get any messier up there.

[Jerry Lowetz]

Or just put your planer by the garage door and open it when you plane. Bonus: Line up half a dozen box fans behind you blowing out.

I'd think the neighbor's dust collector, along with some fresh air ventilation (filtered fan blowing on you? Above opened door blowing out?) would work if you're trying to not spend a bunch on dust collection.

I'm in the same boat, too many actual tools I want to be dropping 2k on dust collection yet!

I have several other things going and according to my (questionable) air quality sensor it's not bad at all.

[Peter Christensen]

Jerry where you live has a big influence on what dust collection and how fast you get it. Guaranteed you'll only open your shop once to plane wood at 40 below.

[Larry Frank]

Just a note about filter pressure. I use a Magnahelic gauge to monitor filter pressure. I bought it used on eBay and not expensive.

The filter pressure will also vary depending on the flow. The higher the cfm the higher the filter pressure with the same filter conditions.

[michael dilday]

1.5 will probably be marginal for your shop. Like previously said if the price is right give it a try and upgrade later if needed. The invisible dust is the dangerous dust for your health so don't gauge performance on what you see. A particle meter would tell you if it is doing the job or not.