PowerPro Thermal Performance

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RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

edma194 wrote: Wed Sep 07, 2022 6:09 pm I'm not convinced all the excessive heat is a result of the belts.
Ed,

I would like to know how you explain rat1932 (Bob's) findings on his PowerPro from 4 years ago. I posted it already on this thread but again below are his MAJOR drop in belt temps after adjusting his belt tension. Please re-read what rat1932 posted and give feedback.
rat1932 wrote: Tue Aug 28, 2018 5:25 pm As a result, the temperature of the upper belt after 30 minutes of runtime has gone from above 180 to 122 degrees. The motor belt has gone from 140 degrees to 119 degrees, the upper bearing was 145 degrees to 99 degrees, and the electronics box was 96 degrees. The ambient temperature in the shop was approximately 72 degrees.

Bob
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edma194 wrote: Wed Sep 07, 2022 6:09 pm The iron core of the motor will not transfer heat as well as the copper coils on inductance motors so I would expect the PowerPro motor to reach a higher temperature than the conventional ones.
Ed,

What??? The PowerPro has a switched reluctance motor so the motor architecture is different from a standard induction motor, but it still has copper coils internally, not iron.
📶RF Guy

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edma194
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Re: PowerPro Thermal Performance

Post by edma194 »

RFGuy wrote: Wed Sep 07, 2022 7:00 pm
Ed,

I would like to know how you explain rat1932 (Bob's) findings on his PowerPro from 4 years ago. I posted it already on this thread but again below are his MAJOR drop in belt temps after adjusting his belt tension. Please re-read what rat1932 posted and give feedback.
I'm sure his belts were getting very hot but that doesn't have to be the only source of excessive heat. The warning is clearly coming from a sensor in the power supply or motor, the belts may not be the only way that overheating condition occurs. I wouldn't be surprised if that brick of a power supply isn't getting extremely hot without excess belt heating.
Ed,

What??? The PowerPro has a switched reluctance motor so the motor architecture is different from a standard induction motor, but it still has copper coils internally, not iron.
The rotor of a reluctance motor is a piece of iron. The coils are only on the stator. This is similar to a stepper motor. The rotor is denser and doesn't transfer heat as well as the rotor coils in an induction motor. Reluctance motors can have higher energy density than AC induction motors and even permanent magnet motors. Some predictions have reluctance motors replacing the permanent magnet motors that have been used in electric cars to reduce weight and to reduce costs because iron costs much less than permanent magnets.
Ed from Rhode Island

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RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

edma194 wrote: Thu Sep 08, 2022 12:49 am I'm sure his belts were getting very hot but that doesn't have to be the only source of excessive heat. The warning is clearly coming from a sensor in the power supply or motor, the belts may not be the only way that overheating condition occurs. I wouldn't be surprised if that brick of a power supply isn't getting extremely hot without excess belt heating.
Ed,

Thanks for repeating back to me what I have already been saying on this thread already. ;)
edma194 wrote: Thu Sep 08, 2022 12:49 am The rotor of a reluctance motor is a piece of iron. The coils are only on the stator. This is similar to a stepper motor. The rotor is denser and doesn't transfer heat as well as the rotor coils in an induction motor. Reluctance motors can have higher energy density than AC induction motors and even permanent magnet motors. Some predictions have reluctance motors replacing the permanent magnet motors that have been used in electric cars to reduce weight and to reduce costs because iron costs much less than permanent magnets.
Ed,

I haven't studied motor design since college, but there are truths to what you say above and inaccurate assumptions as well, I believe. The problem is there are many different types of these switched reluctance motor designs. As I understand it, it can be difficult to get a 1:1 comparison of efficiency (and hence thermal effects) for these different motor designs. Efficiency depends on the quality of the drive-current waveform, but often an assumption is made of pure sinusoidal waveforms. In the Striatech design (for the PowerPro), this is far from the case because it is an inverter drive design which has waveforms with a lot of high frequency harmonics so the waveform applied to the rotor is nowhere near sinusoidal. Below is an excerpt from just one online review on the Striatech DVR motor design, but I have seen other claims elsewhere related to similar swithced reluctance motor designs. The claims are that this particular design yields less heat (motor + power supply module) compared to an induction motor design. You don't get a 50% energy savings with switched reluctance motors and yet have higher thermal by comparison!!! Won't happen. Bottomline is neither of us are experts on switched reluctance motors and we could argue over this design until the cows come home. :D

P.S. NOTE that the Striatech DVR motor CAN be direct drive so we actually don't need all of that loss in efficiency and increased thermal from the belts, but unfortunately the PowerPro has this to make it work in the old headstock form factor. For example, the lathes and drill presses that use the Striatech DVR motor design do NOT have belts and ARE direct drive, so again we come back to discussing belts and their associated heat! :D :D :D

P.P.S. IF you want to improve the PowerPro thermal performance, it is simple - remove the belts! :D

Excerpt from a review on the particular design of the Striatech DVR motor (same as PowerPro):
"Externally a DVR motor looks no different than a conventional motor. But inside you won’t find permanent magnets, brushes, or electrical connections to any moving parts. As well, there is no current flow in the rotor, which means less wear, less heat, and a much longer service life. What you will find inside a DVR motor is a micro-processor that constantly monitors motor load and adjusts power to accommodate the changing load status – it can increase and decrease motor seed (RPMs) depending on the load. This results in energy savings that can be as high as 50 percent over a conventional motor. The micro-processor can also store information on different speed settings and switch from one speed to another with the press of a button.

Another significant advantage of a DVR motor is that it can accommodate a wide range of motor speeds, from as low as 50 RPM through to 100,000 RPM. Because the DVR motor is mounted directly to the drive shaft there is no need for belts or pulleys, and the associated loss in power due to friction, vibration and heat. DVR motors also feature Electro Magnetic Boost, which enables the motor to produce the highest torque at the lowest speed, and more constant torque over a wide range of speeds."
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
Porter Cable 12" Compound Miter Saw | Rikon 8" Low Speed Bench Grinder w/CBN wheels | Jessem Clear-Cut TS™ Stock Guides
Festool (Emerald): DF 500 Q | RO 150 FEQ | OF 1400 EQ | TS 55 REQ | CT 26 E
DC3300 | Shopvac w/ClearVue CV06 Mini Cyclone | JDS AirTech 2000 | Sundstrom PAPR | Dylos DC1100 Pro particulate monitor
DLB
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Re: PowerPro Thermal Performance

Post by DLB »

Jumping back to the Shopsmith PowerPro planing test description, I see Tom's results as perhaps in the normal range. The test refers to 'one-hour increments', not to the length of the rest periods between them or how much actual work was done in any one hour. The machine is working hardest, generating the most heat, when it is actually cutting. At 12 fpm, that's for 40 seconds per 8 foot board. I arbitrarily pick a 50% duty cycle between actively cutting and not to allow for moving materials around, making depth of cut adjustments etc. That's 360 linear feet in each one hour increment, it is going to take 14 hours and 40 minutes to complete a mile. Call it 15 one-hour increments, over a period of "several weeks." Sounds like one 'one-hour increment' per workday. Even if there were two per day, one at the beginning and one at the end of the shift, that's a pretty good cooling off period between increments.

I looked these results up because I initially thought Tom's results were inconsistent with known PP performance. There is no reason to think they are. The planing test performed by SS was not necessarily more demanding. As has been pointed out, you have to factor in the environment. You also have to factor in whether the machine was in a warm state at the start of the planing task. And Tom could have been working the machine harder or less hard than the test.

- David
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