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everettdavis wrote:DVR motors have no rotor windings to fail and overheat where conventional AC and DC motors do and DVR consistently run 80% more efficient so where's the heat generation actually coming from?

Everett

Neither does an induction motor.

Both have stator windings.

The DVR motor has stator windings that will burn up in an instant if pulsed too long.(the inductance limits current during short pulses).

I hate using a poor analogy, but computer processors heat up more if run faster.(I say poor because there is a different cause).

Also there is a power supply, and speed controller(turning those pulses on/off) that generates heat.

When the motor runs slowly there is more time between pulses for cooling to take effect. There may be a greater percentage of 'off' time compared to pulse duration.[duty cycle](I simply do not actually know that)

Then there is the heat generated by the belts on the pulleys. Faster creates more latent heat in both the pulleys and the belts themselves.

Latent heat buildup is a somewhat insidious phenomenon it that is is 'self feeding'. i.e. hot makes even hotter.

For reference, an induction motor is not very 'efficient' to begin with.

I also wonder if the fan effectiveness becomes less with increasing RPMs.

Rambling with no attempt to 'solve' the problem.

80% more efficient than what? Where did you see that stat?

As for the heat generation, see this post. It's a fairly complex phenomenon, but well understood by motor and transformer designers. Did you know that large transformers must be specified not only by volt-amps, but also by the harmonic content of the load? If you use a garden-variety transformer to supply a whole bunch of devices with rectifiers on the front end, you have to greatly de-rate the transformer.

Talked with Wes this evening. He walked me through increasing the temperature threshold for the warning. This is just a bandaid while I wait for my box to send it back to them.

He is going to talk to customer service tomorrow to send me a loaner while I wait for mine back.

Something, something about the power supply. At least we are moving forward, finally. ::thumbs up::

BuckeyeDennis wrote:80% more efficient than what? Where did you see that stat?

As for the heat generation, see this post. It's a fairly complex phenomenon, but well understood by motor and transformer designers. Did you know that large transformers must be specified not only by volt-amps, but also by the harmonic content of the load? If you use a garden-variety transformer to supply a whole bunch of devices with rectifiers on the front end, you have to greatly de-rate the transformer.

Sorry I missed this post til now.

The quote comes from http://teknatool.com/dvrm/

It's in the section heading:

Teknatool Invited to showcase DVR technology at the prestigious APRA-e energy summit, Washington D.C. Feb 2013

That's pretty much what I figured -- BS from the marketing guys.

To put this in perspective, the design project I'm working on right now involves spinning a metal-cutting tool at 15,000 RPM. Which is a pretty good challenge for bearings of the requisite diameter. So we are working with the most reputable U.S. bearing manufacturer on the design of this thing, and can cost-justify their very best bearing technologies. Their marketing literature says that their bearings are capable of 15,000 RPM with grease lubrication ... which would be wonderful, and make our job fairly easy. BUT, one of our consultants knows the design engineers at that bearing company. So he calls them up and discusses our application. And is told by the engineers that 15,000 RPM with grease lubrication is a pipe dream. Unless maybe it's on an ICBM, and the bearing only needs to last for 20 minutes or so. In the real world, 15,000 RPM is doable, but it requires an oil-delivery system. Which isn't nearly so easy.

Marketing guys routinely distort the engineering specs for competitive purposes. Their competitors do it, and if they don't follow suit, they're hosed. So always take marketing specs with a large grain of salt.

BuckeyeDennis wrote:That's pretty much what I figured -- BS from the marketing guys.

To put this in perspective, the design project I'm working on right now involves spinning a metal-cutting tool at 15,000 RPM. Which is a pretty good challenge for bearings of the requisite diameter. So we are working with the most reputable U.S. bearing manufacturer on the design of this thing, and can cost-justify their very best bearing technologies. Their marketing literature says that their bearings are capable of 15,000 RPM with grease lubrication ... which would be wonderful, and make our job fairly easy. BUT, one of our consultants knows the design engineers at that bearing company. So he calls them up and discusses our application. And is told by the engineers that 15,000 RPM with grease lubrication is a pipe dream. Unless maybe it's on an ICBM, and the bearing only needs to last for 20 minutes or so. In the real world, 15,000 RPM is doable, but it requires an oil-delivery system. Which isn't nearly so easy.

Marketing guys routinely distort the engineering specs for competitive purposes. Their competitors do it, and if they don't follow suit, they're hosed. So always take marketing specs with a large grain of salt.

BD your last paragraph is sooo true, makes it tuff on the guys that are suppose to make it happen like you I assume/guess.

ERLover wrote:

BuckeyeDennis wrote:That's pretty much what I figured -- BS from the marketing guys.

To put this in perspective, the design project I'm working on right now involves spinning a metal-cutting tool at 15,000 RPM. Which is a pretty good challenge for bearings of the requisite diameter. So we are working with the most reputable U.S. bearing manufacturer on the design of this thing, and can cost-justify their very best bearing technologies. Their marketing literature says that their bearings are capable of 15,000 RPM with grease lubrication ... which would be wonderful, and make our job fairly easy. BUT, one of our consultants knows the design engineers at that bearing company. So he calls them up and discusses our application. And is told by the engineers that 15,000 RPM with grease lubrication is a pipe dream. Unless maybe it's on an ICBM, and the bearing only needs to last for 20 minutes or so. In the real world, 15,000 RPM is doable, but it requires an oil-delivery system. Which isn't nearly so easy.

Marketing guys routinely distort the engineering specs for competitive purposes. Their competitors do it, and if they don't follow suit, they're hosed. So always take marketing specs with a large grain of salt.

BD your last paragraph is sooo true, makes it tuff on the guys that are suppose to make it happen like you I assume/guess.

Usually not, surprisingly enough. There seems to be an unwritten rule that the engineers generate the numbers for the datasheets, which are generally too dry and arcane for anyone but another engineer to consume. And thus they can almost always be relied upon. I've only been let down by engineering datasheets a couple of times in the last 40-odd years. The marketing literature that is aimed at the end user, on the other hand, is a whole different story.

Read 'specifications' on 'line' lately. Totally devoid of meaningful 'dry' stuff. Often merely repeats what was on the 'home' page or the physical dimensions.

I wonder what bearings and lubricants they use in the new Dyson handheld..... using DSR motors (Digital Switched Reluctance opposed to Digital Variable Reluctance) .... 104,000 RPM. I wonder if those bearings would scale up to the large motors....

-excerpt-
"... inside the new Dyson DC31 vacuum cleaner is a motor that's ten times faster than a jet engine, and much quieter. At 104,000 rpm, the DC31's digital switched reluctance motor actually spins faster than any motor on earth.


Powering the device is the second-generation Dyson Digital Motor (DDM), which weighs just 139g and measures 55m in diameter. Compared to conventional motors, which use carbon brushes that spark to create the rotations, the DDM uses a a stator that creates a strong electromechanical field, which is then switched digitally using an on-board microprocessor."

http://www.popsci.com/gear-amp-gadgets/ ... motor-ever

Everett

My $.02