Voltage Calculation of Electric Element

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qsm_hameed Participant Join Date: Dec 2007 Posts: 1	Voltage Calculation of Electric Element 12/27/2007 2:44 PM
	I want to calculate the voltage of electric element which will maintain the the temperature of box beteween 30C to 90C plz let me know if anybody knows
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CSM Engineer Guru Join Date: Sep 2007 Location: Reno, NV (USA) Posts: 608 Good Answers: 66	#1 Re: Voltage calculation of electric element 12/27/2007 2:58 PM
	First you need to do some heat transfer calcs and figure the wattage required to maintain your temperature. You'll need the size of your box, the ambient temperature and K-factor (insulation) of your box material to accomplish this. After that: P (watts) = I (current) * V (voltage) Generally you will know what supply voltage is available; you just have to calculate "I" to size your circuit. Or, just match a heater to the wattage you require and check the manufacturer's tag for voltage and current required. But the heat transfer calculations have to be done first. __________________ Aequam memento rebus in arduis servare mentem.
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garth Guru Join Date: Sep 2006 Location: NSW Australia Posts: 1101 Good Answers: 23	#2 Re: Voltage Calculation of Electric Element 12/28/2007 7:04 AM
	Place your element in the box , place a temp sensor where you wish to measure same . Supply your element with a variable voltage transformer or variable DC voltage slowly bring the voltage up till you attain 60C fairly constantly then measure your voltage. The temp will vary depending on your ambient temp but should be maintained within the range you specified unless you are in an extreme environment __________________ Dont get on to the roundabout if you dont know how to get off
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TVP45 Guru Join Date: Jul 2007 Posts: 4448 Good Answers: 143	#3 Re: Voltage Calculation of Electric Element 12/28/2007 12:25 PM
	Go to some of the heater vendor sites (Wattlow, Chromolox, etc) and look for calculation aids, or the field service guys can do this for you sometimes. Some of the box manufacturers also will help. Have you looked at Hoffman, for example? The most important thing is ambient, especially wind. You can also insulate the box if need be. You'll likely want to use some kind of controller, possibly in PWM. __________________ "Well, I've wrestled with reality for 35 years, Doctor, and I'm happy to state I finally won out over it." Elwood P. Dowd
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#4 Re: Voltage Calculation of Electric Element 01/02/2008 8:58 AM
	Any heater that is rated to exceed the power dissipated from the outside of the box at 90degC will do the job, provided the box is equipped with some sort of measurement and control device that switches off >90degC and switches on <90degC (the temperature tolerance will dictate the level of refinement needed here). Heat transfer calculations can, at length, achieve a theoretical solution that is correct for the assumptions that are made at the starting point. The practical solution is to try it, and see what happens, adjusting and modifying the equipment and repeating the experiment as necessary. Is there scope to insulate the outside of the box so as to reduce the demands placed upon the heater (rhetorical question)? __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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