I am building a circuit that runs off of 220V (it will be implemented in Peru), and is going to have 5 heat cartridges in total, with each of the same wattage, that we want each one to reach a temperature of around 400 degrees F on the outer surface.

We have experimented with the watt rating for each cartridge but we only have a few sample cartridges. The one we mainly tested was rated at 250W and reached a temperature of 600 degrees F, which is too much.

We are going to try to use a 220V light dimmer to reduce the voltage on the circuit so that the amount of watts is more controllable. Does anyone know how we could calculate the temperature on each of the 5 heating cartridges from the amount of voltage that we let go into the circuit?

We aren't set on if we want to put the cartridges in series or parallel. That might be a big factor in how much voltage we put in.

Thanks for the much appreciated help!

 

Normally heating devices rather than controlled dimmer style Triac control, burst firing method is used, this way you can use a standard SSR.
In any case some kind of PID controller may be needed if you require accurate control.
There are small PID controllers out there that use a thermocouple for sensing and can control the SSR.
Omega is one source of components.
Max.

 

Your question cannot be answered without knowing how much heat s being lost. With electronic components, for example, a rating such as °C/W is given for thermal performance. Then knowing the wattage, once can calculate the temperature rise. Heat sinks have a similar rating based on free air or moving air and so forth.

In your case, you might consider doing a calibration curve. That is, take your device with the 5 cartridges, set your light dimmer at some convenient setting and measure the final temperature. Repeat for a few settings, and you can get a decent curve for temperature rise/setting. You could also determine the watts supplied for each setting, but I am not sure you need to do that. Remember, the final temperature will vary with any change in conditions that changes the rate at which heat is taken away.

John

 

how much accuracy do you require?
Assuming you want a fairly accurate/stable 400 deg over changing ambient conditions,etc... then doing as max suggested above is a must..
temperature controller/ssr/thermocouple..
You can get them cheap on ebay..like this
http://www.ebay.com/itm/Digital-PID...229?pt=LH_DefaultDomain_0&hash=item1c4ac2d2d5

 

My suggestion would be to start here and get a handle and understanding of Watt Density. A further Google of Watt Density and Heater Selection Guides will get you more information. You really can't use a dimmer in a set it and forget it type design, you will need a means of control and depending on how tight you want to maintain a 400 degree temperature it can be as simple as On/Off control or a more elaborate PID type control. Finally, while you don't mention it if a triac for example shorts in the control you may want to think about an over temperature shutdown arrangement in your design. Without knowing more about the exact application in detail it's hard to say more but I would start with watt density.

Ron