Is there any evidence of ventilation devices?

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Thu Jan 10, 2019 1:05 pm

Eek! I mis-explained it above. The no-load motor speed is an upper limit for the fan speed. The fan puts a load on the motor - the most important load being the air it pushes - and this lowers the speed of the fan from the motor's no-load speed.

I was thinking about it slightly incorrectly - as evidenced in these posts. But this is what I think now.

So the horsepower rating of a fan is a measure of how much air it can move.

Since the torque is essentially constant for an AC induction motor, the horsepower of an electric fan is proportional to the speed of the fan.

In the instance Mattogno cites, the 2 fans have the same speed so the higher horsepower fan moves more air. Such is the case regardless of the duct-work or whatever. The fan with the higher horsepower is rated a higher horsepower BECAUSE it moves more air.

How much air any fan of a particular horsepower rating moves in any particular geometry it is put into is up for debate - but NOT the fact that the higher horsepower fan moves more air. Or in the words of Mattogno's article, the higher horsepower fan has a greater "capacity" than the lower horsepower fan. Such is the simple fact of what the horsepower rating of a fan IS.

Discussing the working of an AC induction motor to try to prove something contrary to these simple facts I've just stated here in this post comes across as weird quackery to normal human beings.

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Fri Jan 11, 2019 2:29 pm

Oh crap, the torque isn't constant! I was thinking of Tesla's AC induction motor. Apparently the reason that motor attains constant torque is through frequency modulation. So I'm thinking about it all wrong. Apparently the load does indeed give a counter-torque to the motor - inducing more current (which makes sense now that I think about it, duh). I have to rethink this one.

EDIT: But I STILL think that a higher rated horsepower motor necessarily moves more air because of the fact that it is higher horsepower. IOW 2 motors in the exact same conditions - with one higher horsepower than the other; then the higher horsepower one would be moving more air. I can't see how otherwise could possibly be the case.
Last edited by blake121666 on Fri Jan 11, 2019 2:39 pm, edited 1 time in total.

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Re: Is there any evidence of ventilation devices?

Post by Huntinger » Fri Jan 11, 2019 2:31 pm

blake121666 wrote:
Fri Jan 11, 2019 2:29 pm
Oh crap, the torque isn't constant! I was thinking of Tesla's AC induction motor. Apparently the reason that motor attains constant torque is through frequency modulation. So I'm thinking about it all wrong. Apparently the load does indeed give a counter-torque to the motor - inducing more current (which makes sense now that I think about it, duh). I have to rethink this one.
Blake if you can, can you think of how fluid below ground level can be taken to a tank some one metre higher. The fluid level of the Leichenkeller is a huge issue.
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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Fri Jan 11, 2019 9:39 pm

Here is a summary of the part of Mattogno's article being discussed here. I had to read the article again to reacquaint myself with what the argument even is.

Under section II of Mattogno's article

1. For what would become K2, the cost estimates by Topf on 11/4/41 for the 2 fans (intake and exhaust) for morgue 1 said:
Air-blower with the capacity of 4800 m3 of air per hour against a total pressure of 40 mm of water column with a number of revolutions of the blower wheel of n=925 per minute and a power demand, measured at the drive shaft, of 1.6 HP
2. The revised drawings for K2 on 3/10/42 have these fans as being changed to being 3.5 HP (not 1.6 HP).

3. The letter of Bischoff to Topf of 2/11/43 refers to "an air-blower Type 450 with 3.5 HP motor" was missing (not delivered).

4. Topf's reply letter of 2/12/43 claims 2 air-blowers of type 450 were delivered (no horsepower mentioned).

5. The Topf invoice of 2/22/43 refers to a 4800 cbm 2 HP air-blower for K2.

6. The invoices for K3 on 5/27/43 (document 21a, document 21b, document 21c, document 21d) say the same as the invoice for K2 (4800 cbm 2 HP fans).

7. I'm not sure what to make of Mattogno's point 7. Apparently Pressac either saw or assumed that a roof plan of 3/19/43 of K2 shows the fan power output as 3.5 HP. His document 22 is too blurry for me to know what that is.

So the question is: were the K2/K3 fan motors 1.6, 2.0 or 3.5 HP?

In section III, Mattogno says that the invoice for the K4/K5 blowers:
Mattogno, III wrote:Footnote 21 on page 120 refers indeed to the “preliminary invoice [sic] Topf of December 23rd 1943”. Here an air-blower of Type 450 with a capacity of 8,000 m3 of air per hour with a three-phase motor of 3.5 HP is mentioned.
So this later invoice for the 2 other Kremas states that those later Kremas had Type 450 blowers with 3.5 HP motors and a capacity of 8000 cbm each.

So it appears to be the case that a "Type 450" fan with a 2.0 HP motor has a capacity of 4800 cbm and a "Type 450" fan with a 3.5 HP motor has a capacity of 8000 cbm. Topf billed for 4800 cbm capacity fans for K2/K3 but might have actually sent 3.5 HP motors to K2/K3 which are said to have been 8000 cbm capacity in one instance - the invoice for K4/K5 fans.

I am inclined to think that a higher HP motor would result in a higher capacity fan (it'd spin faster and push more air). But I actually AM NOT inclined to think that, all other things the same, a 3.5 HP motor would give the fan (8000/4800 = 1.67) times the capacity of a 2 HP motor. I think it would be much much much less than that. So I don't know what to make of this situation. I'm saying that if a 2.0 HP motor gives 4800 cbm capacity, then I don't think a 3.5 HP motor would give 8000 cbm capacity. I'm thinking more like 5800 cbm or something (the cube root of 3.5/2.0 more). But I'll justify that in a later post.

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Re: Is there any evidence of ventilation devices?

Post by Scott » Sat Jan 12, 2019 1:36 am

Blake, I haven't looked through all this much, but most industrial motors used as workhorses for producing power are in fact "Tesla induction motors" (not talking about Elon Musk's car by that name here, but Tesla's 1882 invention, which was an electric motor using no commutator due to the "rotating magnetic field" of an AC power applied to the stator of the motor). The Nikola Tesla "rotating magnetic field" principle works with single-phase or multi-phase AC power.

AC Induction Motors are brushless, which was Tesla's genius invention. Power is "inducted" from the rotating magnetic field on the stator to the windings/cage on the rotor without any physical electrical connection. And the more that you try to stall the speed of the rotor, the more power will be inducted to compensate for a decrease in counter-emf (countervailing electromagnetic force) on the rotor. The induction motor will thus run slower and draw more power if you load it down.

What this means is that if you apply more mechanical load on the motor, the rotor will slow down and that will increase the power inducted onto the rotor windings accordingly and increase the available torque, thus making the motor speed up to try to catch up with the phasing lag from the "rotating magnetic field" of the AC mains power applied to the stator windings. A three-phase AC induction motor will start easier than a single-phase type because the "rotating magnetic field" principle works better. You don't have an electrical connection to the rotor windings or "squirrel cage" of a Tesla/Induction motor because of the induction of current from the stator windings into the rotor windings, which induces the rotor to spin to try to catch up and follow the rotating magnetic field; this means that there are no slip rings and brushes or "commutator," just a set of shaft bearings. If you load the rotor down mechanically it will turn slower and less counter-emf will be generated thus increasing the torque as the rotor tries to keep up with the rotating magnetic field; this means that the exact rotor speed will depend upon the mechanical load, as it will be impossible for the induction motor's rotor to catch up and remain in perfect synchronicity with the rotating magnetic field on the stator.



With what are called an AC Synchronous Motor on the other hand, the "speed is independent of the load over the operating range of the motor." Larger Synchronous motors are not "brushless" like Induction Motors; they usually have slip-rings to allow a DC bias voltage to energize a rotor winding, with the AC mains power applied to the stator. However, the Synchronous motor in the illustration below has no slip-rings and carbon brushes because it is using permanent magnets for the rotor, which rotates in "synchronous" lockstep with the magnetic field of the 3-phase AC mains applied to the stator. (There are other "exciter winding" variations to prevent having to pass much of the power generated or consumed through either slip-rings and brushes or a commutator and brushes, but I won't go into that.)



A Synchronous motor will run more or less in synchronicity with the rotating magnetic field from the AC mains applied to the stator. These types of motors are not used for industry very much--except as a synchronous "reactor" to capacitively correct the "power-factor" on the AC line when running so many inductive loads. With perfect power-factor correction adjusting the line reactance, the utility needs only to supply an amount of current similar to a purely resistive load and not a superfluous amount caused by wild inductive reactances from various industrial loads on the grid. Synchronous motors have slip rings to apply a DC bias voltage to a rotor winding--and the AC main power is supplied to the stator, to effectively make a rotating magnetic field, which the rotor directly synchronizes with. By adjusting the DC bias on the rotor you can change the power-factor mismatch somewhat on the AC mains in a given application by making the phase lead or lag. Synchronous motors are usually not used as workhorses in industrial applications because they cannot supply as much torque and thus run hotter than brushless Induction motors.

One example of a synchronous motor used in a home might be that of an old-fashioned electromechanical clock; the speed of the clock motor or timer would be "governed" by the AC line frequency--although these clocks actually run slightly slower over time, but never faster.

Most smaller motors, however, are neither Inductive (Tesla) motors nor Synchronous (clock) motors but are the ubiquitous so-called Universal motor. Universal or "series-wound motors" do have a "commutator" to supply switched power to the rotor windings; they are called Universal because you can apply either DC or AC current to them since the commutator switches the polarity of the current as the rotor spins into alternate positions. Sometimes they use permanent magnets on the rotor or stator, or sometimes stator windings configured in series with the rotor windings, aka series-wound. Your car's starter motor is configured this way, and it provides very high torque at a dead stop. A vacuum cleaner motor or one on an electric drill with an AC power cord would be examples of Universal motors--but you seldom see these in large horsepower applications like an air conditioner compressor or a big fan blower; that is what the (Tesla invented) Induction motors are used for. Motor with carbon brushes that pass current through a commutator wear out quickly--as Edison found with his DC generators and motors, compared to the brushless Tesla designs used by Westinghouse and found everywhere today.

As far as the Tesla/Westinghouse type of motor, using AC current also has an advantage in that the voltage can easily be stepped up or down by transformers, with higher voltages able to travel longer distances over power lines than the lower-voltage DC systems used by Edison's electric company. Nowadays it is possible to build brushless electronic rather than mechanical commutators, and these are used in various precision applications like robotics but I won't go into that.

Universal or series-wound motors (that have stator windings wound in series with rotor windings) have high starting torques (especially at DC) which make them useful for certain applications such as starting car engines; they are lightweight for the power they provide, and are not dependent upon power line frequency for speed. The major disadvantage here is that the commutator through which all the electrical power is switched and changed in polarity to the rotor is passed through carbon brushes that will eventually burn out or mechanically wear out.


Below: DC or AC/DC Universal motor with permanent magnet stator and switching commutator for rotor windings.

Image

So, if I understand the arguments correctly, I think the bottom line is that although an AC Induction motor of larger size will not necessarily turn any faster, you can potentially push more air with it because it will have more torque available at a given load. I assume that you might have to optimize the gearing or the fan pitch, however.

Also, an electric motor in English is usually called a "motor," as opposed to a heat "engine" of some kind. An exception would be either a "rocket motor" or a "rocket engine."

Semantically, I'd say that all engines are motors, but not all motors are necessarily engines. Maybe. Because, you might say a "rocket motor" or a "rocket engine," but I doubt that in English you would likely say a "jet motor" instead of a "jet engine." English is weird.

:mrgreen:


[EDIT: This post has a lot of redundancies and I am not really sure that I have made it very clear. But I don't find it too convincing that installing a larger AC Induction Motor into a blower system would not move more air, if that is the hypothesis.]

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Sat Jan 12, 2019 8:49 pm

I haven't read Scott's post yet but here is the argument Mattogno SHOULD have made. My main problem with the argument he DID make is that he assumed that ALL fans spin at an EQUAL rate SOLELY determined by the frequency of the input electricity (to the motor itself). Such is true for an unloaded AC induction motor of the design Mattogno assumes (which is debatable itself) but it is NOT true for the speed of the fan attached to the motor. It spins slower due to the load it puts on the engine.

A much much better argument that Mattogno should have made is to look at the estimate of 11/4/41 for the fan to be used - which was a preliminary estimate for a 1.6 HP fan that would produce 4800 m^3 per hour airflow in the ducts.

Image


Now look at the billing from 2/22/43 for a fan that was installed - which is a billing for a 2.0 HP fan that produced 4800 cbm per hour airflow in the ducts.

Image

So obviously we have here a case of a higher horsepower fan being claimed to have the same airflow rate (what Mattogno refers to as "capacity") as a lesser horsepower fan. The only question - which I haven't looked into for an answer - is whether the geometry of the ducts changed or something like that. But even regardless of that, here we have a case of a higher horsepower fan having the same "capacity" as a lower horsepower fan.

Werd should point this out to Rudolf who should address it to Mattogno. I DO NOT think Mattogno's technical explanation about fan speeds is correct at all, though. And I'll go further and claim quite plainly that if I use the same assumptions that Mattogno used for the motors, the higher horsepower fan would indeed give a greater airflow than the lower horsepower fan in the exact same conditions. Mattogno's explanation (and most likely his assumptions about the motor) is incorrect. He can leave in the part about pressure losses requiring a higher horsepower fan - but take out the motor speed part. The motor speed would be greater for the higher horsepower motor with the same fan.

I am going to leave the matter at this for now - because I unfortunately am not very interested at this time of what the airflow rate actually WAS. But I think it reasonable to say that Pressac COULD be wrong in the way he handled it. These 2 documents show that well enough.

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Sun Jan 13, 2019 3:21 pm

BTW, I thought K4 and K5 were naturally ventilated? What was the invoice for blowers for K4/K5?

In section V of Mattogno' article (discussing this invoice for the K4/K5 motors) he says:
Mattogno V wrote:Since the power output of the motor could not influence the number of revolutions
He says things like this throughout his article. This is a terribly incorrect statement. Two motors of identical design with one having a greater power output than the other would necessarily have the one spin faster than the other. They would only spin at the same rate if the load on the higher HP motor was greater.

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Sun Jan 13, 2019 4:33 pm

Scott wrote:
Sat Jan 12, 2019 1:36 am
Blake, I haven't looked through all this much, but most industrial motors used as workhorses for producing power are in fact "Tesla induction motors" (not talking about Elon Musk's car by that name here, but Tesla's 1882 invention, which was an electric motor using no commutator due to the "rotating magnetic field" of an AC power applied to the stator of the motor). The Nikola Tesla "rotating magnetic field" principle works with single-phase or multi-phase AC power.

AC Induction Motors are brushless, which was Tesla's genius invention. Power is "inducted" from the rotating magnetic field on the stator to the windings/cage on the rotor without any physical electrical connection. And the more that you try to stall the speed of the rotor, the more power will be inducted to compensate for a decrease in counter-emf (countervailing electromagnetic force) on the rotor. The induction motor will thus run slower and draw more power if you load it down.

What this means is that if you apply more mechanical load on the motor, the rotor will slow down and that will increase the power inducted onto the rotor windings accordingly and increase the available torque, thus making the motor speed up to try to catch up with the phasing lag from the "rotating magnetic field" of the AC mains power applied to the stator windings. A three-phase AC induction motor will start easier than a single-phase type because the "rotating magnetic field" principle works better. You don't have an electrical connection to the rotor windings or "squirrel cage" of a Tesla/Induction motor because of the induction of current from the stator windings into the rotor windings, which induces the rotor to spin to try to catch up and follow the rotating magnetic field; this means that there are no slip rings and brushes or "commutator," just a set of shaft bearings. If you load the rotor down mechanically it will turn slower and less counter-emf will be generated thus increasing the torque as the rotor tries to keep up with the rotating magnetic field; this means that the exact rotor speed will depend upon the mechanical load, as it will be impossible for the induction motor's rotor to catch up and remain in perfect synchronicity with the rotating magnetic field on the stator.



With what are called an AC Synchronous Motor on the other hand, the "speed is independent of the load over the operating range of the motor." Larger Synchronous motors are not "brushless" like Induction Motors; they usually have slip-rings to allow a DC bias voltage to energize a rotor winding, with the AC mains power applied to the stator. However, the Synchronous motor in the illustration below has no slip-rings and carbon brushes because it is using permanent magnets for the rotor, which rotates in "synchronous" lockstep with the magnetic field of the 3-phase AC mains applied to the stator. (There are other "exciter winding" variations to prevent having to pass much of the power generated or consumed through either slip-rings and brushes or a commutator and brushes, but I won't go into that.)



A Synchronous motor will run more or less in synchronicity with the rotating magnetic field from the AC mains applied to the stator. These types of motors are not used for industry very much--except as a synchronous "reactor" to capacitively correct the "power-factor" on the AC line when running so many inductive loads. With perfect power-factor correction adjusting the line reactance, the utility needs only to supply an amount of current similar to a purely resistive load and not a superfluous amount caused by wild inductive reactances from various industrial loads on the grid. Synchronous motors have slip rings to apply a DC bias voltage to a rotor winding--and the AC main power is supplied to the stator, to effectively make a rotating magnetic field, which the rotor directly synchronizes with. By adjusting the DC bias on the rotor you can change the power-factor mismatch somewhat on the AC mains in a given application by making the phase lead or lag. Synchronous motors are usually not used as workhorses in industrial applications because they cannot supply as much torque and thus run hotter than brushless Induction motors.

One example of a synchronous motor used in a home might be that of an old-fashioned electromechanical clock; the speed of the clock motor or timer would be "governed" by the AC line frequency--although these clocks actually run slightly slower over time, but never faster.

Most smaller motors, however, are neither Inductive (Tesla) motors nor Synchronous (clock) motors but are the ubiquitous so-called Universal motor. Universal or "series-wound motors" do have a "commutator" to supply switched power to the rotor windings; they are called Universal because you can apply either DC or AC current to them since the commutator switches the polarity of the current as the rotor spins into alternate positions. Sometimes they use permanent magnets on the rotor or stator, or sometimes stator windings configured in series with the rotor windings, aka series-wound. Your car's starter motor is configured this way, and it provides very high torque at a dead stop. A vacuum cleaner motor or one on an electric drill with an AC power cord would be examples of Universal motors--but you seldom see these in large horsepower applications like an air conditioner compressor or a big fan blower; that is what the (Tesla invented) Induction motors are used for. Motor with carbon brushes that pass current through a commutator wear out quickly--as Edison found with his DC generators and motors, compared to the brushless Tesla designs used by Westinghouse and found everywhere today.

As far as the Tesla/Westinghouse type of motor, using AC current also has an advantage in that the voltage can easily be stepped up or down by transformers, with higher voltages able to travel longer distances over power lines than the lower-voltage DC systems used by Edison's electric company. Nowadays it is possible to build brushless electronic rather than mechanical commutators, and these are used in various precision applications like robotics but I won't go into that.

Universal or series-wound motors (that have stator windings wound in series with rotor windings) have high starting torques (especially at DC) which make them useful for certain applications such as starting car engines; they are lightweight for the power they provide, and are not dependent upon power line frequency for speed. The major disadvantage here is that the commutator through which all the electrical power is switched and changed in polarity to the rotor is passed through carbon brushes that will eventually burn out or mechanically wear out.


Below: DC or AC/DC Universal motor with permanent magnet stator and switching commutator for rotor windings.

Image

So, if I understand the arguments correctly, I think the bottom line is that although an AC Induction motor of larger size will not necessarily turn any faster, you can potentially push more air with it because it will have more torque available at a given load. I assume that you might have to optimize the gearing or the fan pitch, however.

Also, an electric motor in English is usually called a "motor," as opposed to a heat "engine" of some kind. An exception would be either a "rocket motor" or a "rocket engine."

Semantically, I'd say that all engines are motors, but not all motors are necessarily engines. Maybe. Because, you might say a "rocket motor" or a "rocket engine," but I doubt that in English you would likely say a "jet motor" instead of a "jet engine." English is weird.

:mrgreen:


[EDIT: This post has a lot of redundancies and I am not really sure that I have made it very clear. But I don't find it too convincing that installing a larger AC Induction Motor into a blower system would not move more air, if that is the hypothesis.]
I only got around to reading this just now. So you think that an industrial 3-phase fan motor at the time would have gearing to achieve the desired torque?

I googled around just now and found this: How To Change The Speed Of A Motor

Perusing that page and the comments, it seems to be the case that the windings of the rotor or changing the rotor itself are two things that affect the speed. And it appears there were variable frequency drives (VFDs) even back then - such as this patent from 1910.

So what do you think of Mattogno's technical claims in his article about fan speed? And I guess more importantly, what was the airflow rate through K2/K3? Should one think that it was 8,000 cbm per hour or 4800 cbm per hour (or something else)?

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Re: Is there any evidence of ventilation devices?

Post by Scott » Tue Jan 15, 2019 1:00 am

I think you would have to know a little something about the specific loading on the motor/fan. A weaker motor might run slower because of the loading, but a stronger motor is not necessarily going to run faster. The fan and the gearing or pulley arrangement is going to have a lot to do with the speed/torque, so it is hard to say.

If you want to make the motor run at different speeds there are a lot of different ways to do this, whether with taps on the windings, or a transformer with different voltage taps, etc.

Auto-transformers or "autoformers" are frequently used as a means of soft-starting large Induction motors; these are like transformers but share primary and secondary windings for special purposes such as voltage regulation. Unlike regular transformer they do not provide electrical isolation nor transfer their power strictly through induction, but they work very, very well for voltage regulation and for soft-starting appliances.

Korndörfer autotransformer starter

Since 1920, the autotransformer starter has been the most popular device for reducing the starting current inrush for induction motors; it provides maximum starting torque with minimum line current.


Another sort of an adjustable variable transformer that is reasonably efficient is called a Variac, a trademark dating back to the 1930's; by adjusting a dial on this special kind of transformer you can vary the 60Hz AC secondary voltage from 0-130 volts, for example, and the one in the picture below will handle 20 Amps.

A Variac or a tapped transformer or autoformer gives us a clean sine wave and not a chopped or a reduced-period sine wave, which is another way of dimming lights or adjusting the speed of various kinds of motors using rheostats or thyristors, a kind of silicon-controlled rectifier network. "Switching" power supplies work along the principle of adjusting the waveform "duty-cycle" using an inverter, and these are lighter in weight than "Linear" power supplies which regulate the output "linearly," and usually have heavy transformers or throttle and waste some of the energy on resistors or a semiconductor heat sink. Switching power supplies are a lot cleaner with respect to electromagnetic noise than in the past, so they are preferred in Amateur Radio and telecommunications applications nowadays, when only heavy Linear power supplies or even batteries would have been the only acceptable regulation method.


Image


Going back to what was mentioned earlier about AC Induction motors--by far the most common for air blower or powerful industrial types of applications--this means basically brushless AC "asynchronous" Inductive motors which do NOT run faster than the frequency of the "rotating magnetic field" applied to the stator. They should not be confused with "synchronous" AC motors or generators/alternators (an example being your car's "alternator" which develops 400 Hz AC that is then rectified to direct current to charge the car's battery, and so on).

So, if two workhorse inductive motors have different capacities and are unloaded, the larger one will not run any faster given the same gearing, but the smaller one might run considerably slower when equally loaded.

In either case an Inductive motor will always "lag" some amount behind the rotating magnetic field of the AC mains, depending on the applied load. One reason that the starting current is so high is because the rotation lags so far behind that no countervailing-EMF has been "induced" yet to cancel the surging inrush current. The AC Induction motor will consume its least amount of power when it is running at top speed and unloaded.

https://en.wikipedia.org/wiki/Induction_motor

Whereas a synchronous motor's rotor turns at the same rate as the stator field, an induction motor's rotor rotates at a somewhat slower speed than the stator field. The induction motor stator's magnetic field is therefore changing or rotating relative to the rotor. This induces an opposing current in the induction motor's rotor, in effect the motor's secondary winding, when the latter is short-circuited or closed through an external impedance.[28] The rotating magnetic flux induces currents in the windings of the rotor;[29] in a manner similar to currents induced in a transformer's secondary winding(s).

[...]

For rotor currents to be induced, the speed of the physical rotor must be lower than that of the stator's rotating magnetic field ( ns ); otherwise the magnetic field would not be moving relative to the rotor conductors and no currents would be induced. As the speed of the rotor drops below synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the windings and creating more torque. The ratio between the rotation rate of the magnetic field induced in the rotor and the rotation rate of the stator's rotating field is called "slip". Under load, the speed drops and the slip increases enough to create sufficient torque to turn the load. For this reason, induction motors are sometimes referred to as "asynchronous motors." [31]


Btw, this same Wikipedia article on Inductive motors states that "full load motor efficiency varies from about 85% to 97% [...] " which is about in the same ballpark as my "field training exercise" rule-of-thumb figure (67 percent) that I remember from my days when I actuality did technician work in the Signal Corps and in broadcasting and telecommunications.


In other words, with about a two-thirds conversion efficiency with your motor or generator/alternator, if you need 746 watts of electrical or mechanical power, you will need to supply, not 1 brake horsepower, but about a third more--so 1 mechanical horsepower gives you only about 500 watts instead of the theoretical 746 W and vice-versa. These are "practical ballpark figures" and not precise figures, of course.

:)

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Re: Is there any evidence of ventilation devices?

Post by blake121666 » Tue Jan 15, 2019 9:16 pm

So the question is: Why would one choose a higher horsepower motor in a particular HVAC application (air exchanges of a room through duct-work)?

P = T x w

where P = output power, T = torque, w = rotational speed of shaft.

So wouldn't it be the case that a higher horsepower fan would have higher T and/or w? Or could it be the case that there would be power losses associated with a greater load on the motor - necessitating a higher torque motor for better efficiency? I think this is what Rudolf was saying. But this is not what Mattogno describes. Mattogno writes as if the speed is ALWAYS the rated speed regardless of the load. But an overloaded motor would run slower than its rated speed (it's putting its power into T and reducing w).

But on the other hand, if one wished to push more air, you'd need a higher horsepower motor to do that. If the fan stays the same and the speed stays the same you wouldn't be pushing more air if the environment is the same (same pressure), would you?

So maybe Mattogno is correct - simply not in the way he seems to be explaining it. If the fan stays the same and the motor speed stays the same, the higher horsepower is going into the T of the motor. That fan would push the same amount of air if it is spinning at the same speed in the same environment (same pressure) though.

But the K4/K5 motors ostensibly have the same speed, pressure, and fan and are rated at 8,000 cbm per hour - vs the 4800 cbm per hour of the K2/K3 fans.

Some other piece of information is needed to explain this.

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