Magnetic Field from Heater?

I don't know which standards apply to either you or to your customer, but here's a link to EMI that might get you started.

http://www.radioing.com/eengineer/index.html

Your heater configuration, enclosure and your control scheme will have a definite influence on radiated EMI.

Also, if you use zero crossing switching SSRs it is better.

well of coarse ther will be a magnetic field produced somewhere - if electric current is flowing, then magnetic field lines are forming. As to the magnetic field being strong enough to interfere with their equipment, highly doubtful unless their 'recording equipment' is the device being used to try to find a gravity wave and they have it mounted really, really close to the heater. you can check it out with a regular, decent compass. see where you get any deflection or vibrating of the needle -then back away 1/8 inch and you won't see any trace of interference. the strength of a magnetic field at a given point is inversly proportional to the distance to the source squared (it drops of very rapidly)

Hi,

Assuming you just have loops of wire or coils of wire generating heat, there will be a magnetic field, however, it is surely very, very small. IF it were a problem, it can be improved by the way the wires are wound, or the directions they travel in your equipment, but I can't imagine there being any need.

The transportation and logistic groups have made a lot of effort to consider static magnetic (from permanent magnets) for items being air shipped, but, the standards are so low ... maybe only a few times more than the magnetic field of the earth ... that actual measurement is difficult. Some agencies have suggested some very expensive and elaborate equipment, which some have resorted to such crude tactics as "if a paper clip sticks to the outside of the shipping carton, the radiating magnetic field is too high" ... no kidding.

SO, before you invest in any very specialized tests, either in-house, or at an agency (both expensive), you might do something 'easy' to see if there is any great interference from your heater. (don't laugh) Just set your heater next to a CRT or TV and see if the picture 'blooms' or distorts. I'll bet it doesn't. If not, you can (I would) tell your client that the stray field at "X distance" is "nil". If by "recording equipment" your client is referring to magnetic tape or similar, hard drive, or about anything magnetic in nature, if your heater won't effect a CRT, it won't effect their gear.

NOW, back to the comments about FCC testing for inducted or radiated interference, that is a different story, and without knowing more about the electronics used in association with your heater, there is no way to predict. If by "recording equipment" your customer is referring to RF transmitting equipment, they will need to know what is the EMI characteristics of your gear. (expense, time, outside agency) In the end it might be necessary.

Good luck.

As far as your main voltage comsaption is resistive this shouldn't involve any EMI.If there is any EMI it may comes from non-resistive load, we are also heaters manufacturers and we use filter just for controllers and fans but no one for resistive load...and we passed certification

Are your heater elements formed from long coils? if so they can produce a small magnetic field but you can reverse wind every other coil and have a canciling field.

It they are simple U shapes they should not develop enough magnetic force to cause any interferance.

Most interferance on recorders is from radio transmissions and high frequency on TIC welders. Bad grounds of a welding machine can sometimes produce interferance.

Running the thermocouple extension leads next to high amp wires can cause inductive loading causeing false signals on the recorders.

Most interferance is shown on the recorder as sparatic readings.

Thank you, for your input, will forward a few ideas to the client.