Current Regulator

[zj4041]

I am trying to run a custom heater element at its max power capacity 400w. It runs on 110vac. I would like to run it at max power continuously.

What can I purchase or build that will keep the voltage at 110vac but regulate the current such that I am only supplying 400w?

 

[rbulsara]

Buy a voltage regulator! Resistance of the heater will remain fixed so current will remain fixed. What is custom about it?

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

If you are fixated on regulating the current, look up constant current regulators used for airport lighting.

Rafiq Bulsara

http://www.srengineersct.com

 

[Skogsgurra]

If the spec is 110 V and 400 W, then you will have 400 W at 110 V. Nothing to do. I fail to see the problem.

Is it that you have a thermostat that switches off now and then and that you want the heater to run continuously, without the off periods?

If that is so, you may need to consider the risk that your heater will self-destruct or set the surroundings on fire.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[zj4041]

im pretty much bypassing the temperature controller.

Im planning to just use an AC Variable Voltage Output Transformer, and an ammeter to ensure I dont provide more than the rated wattage (400w) other wise the thing sucks up a bunch of power and burns out(experienced that already). hehe.

 

[jghrist]

Unless this is something other than a resistance heating element, keeping the voltage no more that rated will ensure that the rated wattage will not be exceeded.

 

[zj4041]

it is a resistance heater, but some how the feedback sensor caused the heater to over heat till it blew a safety fuse, and since then the heater just keeps shorting, so now i want to switch to a variable voltage transformer so that it doesnt go beyond the rated limit.

 

[Compositepro]

It sounds like you mat be using a PTC (positive temp. coefficient)heater. If you are, that is a different story. These are self regulating to a certain temperature. Regardless of type of heater, if you do not have some kind of temperature control you run the risk of burning something-up.

 

[jghrist]

The fuse may get hot enough to be damaged even if the current does not exceed the heater's rated current. If there is no there is no temperature control, 400 W continuous heating may be too much heat.

 

[zj4041]

yes but even with a pid temperature control i burnt the element. I used its own build in thermocouple for feedback.

so obviously the feedback is no good other wise it wouldnt have overheated/burnt out. To prevent this from happening i am going to use a volt/percentage controller to regulate the power provided to the element. ill have to do some calibration, but its better than going through elements.

(the thermocouple is not exactly where the hottest part of the element is therefore theres a delay in the controls.)

 

[waross]

It sounds as if you have selected the wrong equipment and then misapplied it.
There are a few things you didn't tell us up front that may have been important.
Although you may think that it is obvious that the feedback control doesn't work, it may not be so obvious to the rest of us.
Hire someone who is familiar with the equipment to spot the trouble.
Some PTC heaters draw much more than rated current when starting in a cold ambient.
Many heaters are subject to burn out if the physical installation is not done correctly.
Hire an expert.
This may turn out to be an instance when the cost of an expert is less than the eventual cost of damages and repairs.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rbulsara]

zj4041:

Resistance, Voltage and current is governed by Ohm's law, you keep two of those three constant, the third will remain constant. I still fail to see what is special about what you are doing. Others have eluded to that too. If you are not using up or removing the 400W heat somewhere, you cannot keep that or any amount of heat source on indefinitely. All you need is a thermostat or equivalent.

Rafiq Bulsara

http://www.srengineersct.com

 

[zj4041]

I apologize for expressing my frustration.

I appreciate the advice everyone has given me. Im in a company where engineering expertise & funding is scarce. I wouldnt be in this forum if it werent for this situation.

 

[davidbeach]

Start at the beginning, for a 400W heater to run at 400W continuously there has to be something that absorbs 400W continuously without the temperature surrounding the heating element exceeding the maximum operating temperature of the heating element. If that 400W can't be dissipated you WILL burn out the element without ever exceeding 400W. Forget the electrical side for a while and solve the thermal side.

 

[zj4041]

Qualification Test of a Pressure Vessel

Thermal side:

I need to heat up just the air inside a small vessel up to 900F. The vessel will be pressurized to 350psi. (Flow is optional)

It sounds simple but it has been a challange for me.

My option is to deliver hot air from another source inside the vessel at high pressure low flow.

or

Put an element inside the vessel and heat up the air without radiating excessive heat to the vessel.

 

[waross]

If you had said that at the first...
900F is above the capability of most resistance heaters. To supply the thermal losses may take a heater element temperature somewhat in excess of 900F. Have you considered using a mineral insulated resistance heater?
I type slow.. You owe me 12 cents. Grin
Is your vessel good for possibly 1100F with a safety factor?


Bill
--------------------
"Why not the best?"
Jimmy Carter