Exactly. The same is true of the very real self capacitance of transformer secondary.
No need. I’m quite well aware of the difference between real and apparent power, thank you.
Are you still saying this is the case in an open loop?
Of course, if you connect your ammeter and give current a path to flow, it’s no longer an open loop.
No. Nor was I. The self capacitance of the winding “closes” the loop, to use your terminology, as far as AC is concerned. It’s exactly equivalent to putting a small capacitor across the secondary terminals of an ideal transformer. There is a current–if you prefer, we can more properly call it a displacement current–which flows (apparently) through this capacitance, regardless of whether the capacitance is a property of the winding or a discrete capacitor placed across the secondary.
…errrr…so I should just use a damper or a smaller pulley then…
Try the damper first. If that gives you an airflow that satisfies you, you’re done. If not then use some Liquid Wrench[sup]TM[/sup] and a puller and get the pulley off and put on a smaller one or an adjustable one.
I think that moderatiing the airflow is a much better idea than any electrical tinkering. Is this a squirrel cage blower, or is it a bladed fan?
If it’s a squirrel cage, get an appropriately sized filter canister, like from a shop vac, and put it over the inlet. You can also use small furnace filters, but may need several to dampen the flow sufficiently. This will reduce the flow, and help clean up the dust kicked up by the refurbishing.
If it’s a bladed fan, go with a batch of furnace filters. You may need to get creative in placing any filters, but I think the results will be good, and it’s a lot easier than doing the trigonometric calculations of EMF some yahoo’s in this thread are arguing about.
catsix, I’m glad you are a teacher and helping young minds to grow.
I was also a teacher of starter and generator theory in an aviation school among other subjects, so what?
Please do not teach your students to interchange the words Volts and Amps as you did in some of the threads, they are really going to have trouble in the normal simple everyday world of house wiring and DC circuits on cars and stuff and such.
When you dismiss generators and alternators as having permanent magnet fields, you lay your lack of knowledge in that particular field wide open to criticism. It works against your credibility.
AC motors are different for DC of course, but a stationary flux field cut by moving windings will induce blah blah blah as will the converse. Yes, AC does not really hold still but if you freeze frame it so as to sort out all the different inducements going on at any one time, blah blah blah…
I do farmer mods all the time. I do not leave farmer mods running at someone else’s property while I leave for the night. Not a good habit don’t ya think?
KISS is a good plan when $$$$ are on the line.
Jesus H.
Ah. So when you said “potentiometer”, you actually meant “enormous wirewound rheostat”. You know these things cost like, $500, and places like Radio Shack don’t stock them right? And they run at like 300 [sup]o[/sup]C, right? :rolleyes:
Since the device you’re suggesting has exposed terminals.
Nah, gotta go with Q.E.D. on this one. catsix is fixated on some mid-19th century pre-Maxwell idea. Whether they realise it or not, they’re arguing a point settled about 125 years ago. Q.E.D. is saying (using Heaviside notation, and the symbol “[symbol]”[/symbol]" for the del operator):
“[symbol]”[/symbol] x H = J + [symbol]d[/symbol]D/[symbol]d[/symbol]t", and catsix is saying "no, no, it’s really:
[symbol]"[/symbol] x H = J".
In effect, catsix is trying to argue that current = conduction current, and that displacement current doesn’t exist, or isn’t current, or something like that.
Q.E.D.: You really should go. It’d be like watching Tim Allen doing “Tooltime”. 
This “current through a capacitor” argument is patently ridiculous. From a circuit analysis point of view, all you need to know is
i = C dv/dt (time domain)
which is equivalent to
Z[sub]C[/sub] = X[sub]C[/sub] = (jωC)[sup]-1[/sup] (frequency domain)
The above equations are for an ideal capacitor, and should be burned into the brain cells of every ET and EE.
For a real capacitor Z[sub]C[/sub] ≠ X[sub]C[/sub], and you have to add in other junk such as parallel resistance (to account for leakage), ESL, ESR, etc. Plus there are temperature effects, etc.
Surplus Sales of Nebraska has 300W, 2.93A 35 Ohm monsters for $35. Gang two in parallel and you could have a horribly unsafe, super innefficient, fire-hazard, make-the-UL-guys-piss-their pants solution for only $70.
(They also have a 0-140V 10A Variac for $119.)
My vote is for David Simmon’s “change the pulleys” route.
Oooh look, two guys who Googled arguing with the professor.
Well, I guess I’ll just leave you to your arrogance.
The “two guys that Googled” seem to have genuine knowledge on the topic. Q.E.D. and Desmostylus have both given answers that demonstrate more knowledge then a half-hour of Googling and Cut & Paste can provide.
I have a BS in Electrical Engineering and Computer Science[sup]1[/sup]. I have a hard timing picturing any of my professors (even the CS ones) telling a construction worker that a 600W rheostat was an appropriate solution for controlling the speed of a blower motor on a job site. Out of curiosity, what’s your degree in? Physics?
[sup]1[/sup]Admittedly, my career has taken me down the CS path. But I still play with it enough that I have Horowitz & Hill within arms reach at the moment.
Your intuition is correct; rheostats suck because they’re so inefficient. By definition, a resistor is 100% inefficient.
Catsix, are you an engineer?
Engineers are supposed to solve problems. This generally means:
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Finding a way to accomplish the task. You’ve done this.
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Finding a way for the customer to implement the solution in a reasonable timeframe. Note: getting a non-standard part from a discount electronics house typically implies a considerable delay here.
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Considering alternatives to your solution, particularly those that would cost less. From the estimates I’ve seen on this thread, your solution could cost $70 or $300. This may be unreasonable considering that another solution proposed on this thread would cost less then ten dollars.
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TAKING SOME REGARD FOR CUSTOMER AND PUBLIC SAFETY. A 600 watt resistor (potentiometer) can generate (worst case) 600 watts of heat in a rather small space. Halogen torch lights generate half as much heat and dissipate it about as well as this resistor would if it weren’t cooled by an outside source. The best-case scenario here is that he has the sense to mount it on something that has good thermal insulation and won’t burn, and receives a decent supply of moving air past it from the fan. The worst-case scenario is that this rather dangerous circuit element gets mounted as if it were a switch - in a box, right next to the wooden structure of the house. In addition to proposing a solution with a good chance of causing serious damage, you dismiss this danger essentially out of hand, while claiming significant professional credibility here.
In regards to the OP, I am not an electrical engineer. I’m gonna stay away from the motor for my solution to the problem. Your problem is that the airflow velocity is too high, right? So, let’s play around with the flow a little. You could duct some of this air away from where you’re using it (presumably, in a furnace) and just have it blow around the basement - which would help prevent the stale air common in basements. You could also build a duct with a much larger cross-sectional area at its exit than at its entrance - this would keep the velocity past the fan constant, while reducing it for the application.
(substitute this for the last paragraph of my last post)
In regards to the OP, I am not an electrical engineer. I’m gonna stay away from the motor for my solution to the problem. Your problem is that the airflow velocity is too high, right? So, let’s play around with the flow a little. You could duct some of this air away from where you’re using it and just have it blow around elsewhere on the site - perhaps you could use a flexible duct and have it blow down the back of your shirt? You could also build a duct with a much larger cross-sectional area at its exit than at its entrance - this would keep the velocity past the fan constant, while reducing it for the application.
I’ve satisfied myself that Nina catsix West actually is a (recent) graduate in engineering, and actually does have a job as a system admin/gopher/teacher with a company in Pittsburgh that churns out associate degrees in web development, networking and such. “Professor” is a bit of a stretch, though.