And now you also know one of the reasons why motors used in the lunar and Mars rovers, and in similar applications require so much engineering. ???When there is no atmosphere, you are left with only radiation to get rid of heat buildup.? Of course there is also the problem with it being so cold that bearings shrink and lubricants freeze, so the engineers have to add bearing heaters that utilize radioactive decay to keep parts from sticking. ?I suspect they also have similar problems with hydraulic motors. ? Jerry F. ?
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From: 7x12MiniLathe@groups.io [mailto:7x12MiniLathe@groups.io] On Behalf Of BuffaloJohn
Sent: Wednesday, July 10, 2024 5:45 PM
To: 7x12MiniLathe@groups.io
Subject: Re: [7x12MiniLathe] OT Hot Hot Hot? ? If remember NEMA ia at sea leave I think at 40% humidity.
No, there is NO humidity, it is 40C which is 104F. Also, the first elevation is from 0m to 999m ?
So high you go less cooling.?
No, as you go higher, air is thinner and therefore you need more cooling I have different outside temperature most are 105°F max for maximum horse power. If go hot hotter you need reduce the horse power.
NEMA and IEC motors are rated in degrees C, not degrees F. As I wrote, Class A insulation is rated to 105C. As for HP, that may be a motor curve, but it is irrelevant to the maximum temperature rating of the motor. There is a Service Factor rating that is part of the spec, but that was not added to this discussion. Some motor are designed for higher temperature and altitude.??
This best use formula for air compressor and pump. Machine tools are variable horse power needs.?
Almost all tools are variable power needs, the more the tool works, the more HP is needed. There are places in America that is over 1,000 feet? witch can you trouble with over heating motors
Motors with a Class A rating will be good to 1000m (~3300ft). If you are not pushing the overall rating of the motor, even up to 3000m (~9900ft), the motor doesn't need to overheat.
Dave?
On Wed, Jul 10, 2024 at 03:06 PM, BuffaloJohn wrote:
Nope, that is not how it works. Per NEMA, the maximum ambient temp is 40C (104F). There is a required reduction for altitude? (up to 1000m 40C, up to 2000m 30C, up to 3000m 20C). The IEC ratings are similar - also with a 40C ambient maximum. Based on the motor insulation class (NEMA A,B,F,H), there are temperature limits - referred to as temperature rise based on a maximum 40C ambient (A - 105C, B - 130C, F - 155C, H - 180C)..? THIS IS REALLY IMPORTANT - the maximum value listed by class has a starting point of 40C maximum. For example a Class A insulation class would allow a maximum temperature of 105C so a change of 105-40 = 65C . If ambient is higher that 40C, you still only go to 105C max, you just get less delta T. So - if ambient is 50C, you still only get to to a maximum of 105C. If ambient is 70C, you only get to 105C. AND if you are higher altitude, you have to degrade the maximum temperature because the starting point (maximum ambient) is lower. So, at 2000m, maximum ambient is 30C and you get 65C delta T so your maximum temperature is 95C. You can read about it here: ? It is what motor companies say. There a lot goes to figuring heat transfer.?
It is only a simple way of figuring out the limits.?
Dave?
On Tue, Jul 9, 2024 at 09:16 AM, Chris Albertson wrote: You can’t add temparures like that.? It is not linear. Without going into the science, maybe an easy why to explain it is that the rate that heat moves depends on the difference in temperature. So as a motor changes temparture the cooling rate also changes. Most motor are rated on any machine tool is rated for the rize in temperature.?
So if shop at 80° and motor rated 120° rize.The motor temperature is 200°
Now with today's temperature where I live is 114° plus 120° so now the motor is 234°.
The late great in winter at 70° plus 100° the motor is running at 170°.?
Now in summer the motor or electronic could give you a problem?
Most over look the problems Global warming is doing on motors and electronics in mini lathes and Mills.?
Dave?
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Buffalo John
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Buffalo John
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