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Paxmax

Member
Joined
May 8, 2002
lclark2074 said:
its when you make AC like 50hz, 60hz, 70hz , 90hz most ac moters will run at difrent speeds 3000 rpm ,3600rpm, 4200rpm 5400rpm
and some run at 1/2 that speed or 1/3 of that speed
Yes, it's a common method in the industry to control syncronos motors, i.e. motors that depend on the AC frequency.
However, you need to lower the voltage aswell when you lower the frequency, otherwize the motors coils will fry.
The other way around goes when you increase frequency, you need to slightly up the voltage to get full torque from motor.

It has to do with the motors inductance in the coils. The motor has a really low resistance in the coils and would burn out instantly if it weren't for the inductance. The inductance will hinder the AC just perfect at 50/60 Hz, the result is a proper current.
If you lower the frequency the coils will be exposed to longer "on" times, causing a huge current rush when the coils and cores go into "saturation" state and can't hinder the AC any more.
With higher frequencies above nominal the coils won't get proper current flow with the short "on" times, causing the motor to loose torque. That is a situation you don't want either, when the motor loses sync because lack of magnetic power. That will result in stuttery and jerky motion, possibly destroy both motor and what it drives. [End electro magnetics class]
 

Paxmax

Member
Joined
May 8, 2002
I haven't got the foggiest idea of what type of motor that sits in a phase changer.
Neither do I have knowledge to tell how the phase changer will react to slower revvs. I can't percieve it as harmful to run it slower, but I don't know if it will work as good on slow.
 

HungryForHertz

Member
Joined
Dec 22, 2003
Ultimately what he is doing is completely pointless because under ~-120 C there is no longer an advantage and as you get colder the more of a hamper and hassle it becomes. I should think what he is doing is just completely experimental. Seeing how it could be set up and what temperatures under-load would be produced or if it actually works and doesn’t kill the Silicon.

A group of computer scientists and engineers in Japan found that below ~-120 there are no longer any overclocking advantages and LN2 is as far as you need to go or you are just wasting your time (unless you are doing something ground-breaking). :)
 
Last edited:

chilly1

Registered
Joined
Dec 26, 2003
Cold limit?

IBM found that there is a signifacant increase in switching speed @ or below -200C, they also have a number of patents related to the eradication of condensation.... www.uspto.gov
BTY Hello this is my first post in this forum.....
 
OP
zabomb4163

zabomb4163

Member
Joined
Apr 27, 2002
chilly1 would you mind elaborating on the design of the system?

does the system need to be recharged?
 

drewmister

Member
Joined
Jan 7, 2004
Location
Cheyenne, Wyoming
just wow just wow.....

helium compressed.... i mean not to be like uhh putting down the project but uhh overkill? I mean no matter what kind of volt modd etc etc you just can't push hardware that far..... I mean what phase change cooling systems that are working correctly are actually having heat being the source of not being able to overclock? The limitations are the hardware not the cooling.... sure it is a COOL idea... but I have to say if you overclock and your load temp is -5C then it is not temp keeping you back... It just the limitations of the hardware.....

anyone else consider the different rates of expansion/ compression of the materials used in the motherboard and processor...

silicon, plastic cpu socket, metal.... all expand and contract at different rates....

extreme temp change + different expansion rates = stress between materials = crack / break

but then again if it works out and everything works....

WOW
 

squeakygeek

Member
Joined
Jan 19, 2003
Location
University of Illinois at Urbana Champaign
drewmister said:
just wow just wow.....

helium compressed.... i mean not to be like uhh putting down the project but uhh overkill? I mean no matter what kind of volt modd etc etc you just can't push hardware that far..... I mean what phase change cooling systems that are working correctly are actually having heat being the source of not being able to overclock? The limitations are the hardware not the cooling.... sure it is a COOL idea... but I have to say if you overclock and your load temp is -5C then it is not temp keeping you back... It just the limitations of the hardware.....

anyone else consider the different rates of expansion/ compression of the materials used in the motherboard and processor...

silicon, plastic cpu socket, metal.... all expand and contract at different rates....

extreme temp change + different expansion rates = stress between materials = crack / break

but then again if it works out and everything works....

WOW

The main point in doing this is to find out what will happen.
 
OP
zabomb4163

zabomb4163

Member
Joined
Apr 27, 2002
drewmister said:
... but I have to say if you overclock and your load temp is -5C then it is not temp keeping you back... It just the limitations of the hardware.....


you obviously do not frequent phase change forums much. there is a world of difference between a -5C oc under load and a -50C oc under load.

do you think it is some crazy coinisidence that all the people using cascades are in the top 10 or that the ONLY 4.7ghz+ overclocks were done using lower than -60C cooling.

you also skipped over chilly1's post
chilly1 said:
IBM found that there is a signifacant increase in switching speed @ or below -200C,
 

drewmister

Member
Joined
Jan 7, 2004
Location
Cheyenne, Wyoming
well i'll come out and admit it i am very new to oc forums and i am very very new to phase change cooling... I dont own one but plan on building one sometime in the future (when i get enough money for a new rig). Why the better performance between -5c and -50c because it obviously not overheating? Is it just that electricity flows better in colder environments (therefore faster processing in the chip)?

just interested to see the benefits of such low temps...
 

squeakygeek

Member
Joined
Jan 19, 2003
Location
University of Illinois at Urbana Champaign
drewmister said:
well i'll come out and admit it i am very new to oc forums and i am very very new to phase change cooling... I dont own one but plan on building one sometime in the future (when i get enough money for a new rig). Why the better performance between -5c and -50c because it obviously not overheating? Is it just that electricity flows better in colder environments (therefore faster processing in the chip)?

just interested to see the benefits of such low temps...

Everything has lower electrical resistance when it's colder. Think superconductors. Traditionally, as the processor gets hotter, we increase the voltage to overcome the increased resistance, but that can only go so far.
 
OP
zabomb4163

zabomb4163

Member
Joined
Apr 27, 2002
http://www.ocforums.com/showthread.php?s=&threadid=244764&highlight=silicon+resistance
explanation


explanation of cpu voltage
-think of the lines as signals

+ = + = = + =

its easy to tell the +'s and ='s appart......jack up the clockspeed
now we have signals closer together AND more signals overall with the same amount of power.....meaning they are small and closer
+=+==+= .....now its a little more difficult

now if we raise the voltage the signals get stronger and thus easier to tell apart.

+=+==+=

temperature is important for 2 reasons
1) silicon melts at high enough temps
2) resistance rises with temperature. higher resistance means weaker signals for the same amount of voltage.



silicon and germanium have a negative temperature coefficient of resistance . meaning......resistance decreases with increasing temperature. our copper's resistance on the other hand increases with increasing temperature.

Combine these 2 facts and it becomes obvious why lower temperatures are better for processors.

lower temperatures mean our insulator is more effective and our copper has less resistance..... thus allowing for more voltage without errors. which is why phase change users are able to user higher voltages more effectively.

raising the voltage increases the risk signals pass through the insulator. combine this with lower resistance insulator and higher resistance copper and it becomes obvious why oc'ed systems cannot tolerate the high temperatures that a cpu at stock voltage will.

if you do not believe me. undervolt your processor then turn off your case fans. your processor will be stable at higher temperatures than it was with higher voltages.
*edited*

(i know the thread a linked was refering mostly to cpu voltage, but the issue of temperature and resistance came up in the thread)