Electromagnetic coils in one form or another are used as solenoids for the gas valve for your clothes dryer or your furnace to the low voltage transformer for your air conditioner or fluorescent light fixture. Recently these electromagnetic coils have been failing more frequently due to either none or very little quality control in the countries in which they are manufactured. To save money on copper these coils are manufactured very close to their threshold of failure. Design specifications require most of these coils to stay on continuously or at least for very long periods and still remain relatively cool or at least NOT hot to the touch. An electromagnetic coil basically consists of a copper conductor (wire) covered with a high electrical insulation varnish formulation. This copper wire is wound like a reel or spool forming the coil. Ideally the length of the copper conductor should be long enough to achieve its purpose plus a little to spare. This keeps the coil from overheating and from reaching something called "core saturation" which is basically the maximum capacity of current it can handle. When enough copper is used the coil isn't anywhere near saturation - and thus runs relatively cool, it will last essentially forever. On the other hand when there ISN'T enough copper conductor used ,"core saturation" is reached causing a build-up of high temperature which eventually in time causes the insulation varnish formulation to break down gradually increasing the current leakage and even arching and humidity absorption. This leads to decrease of resistance across the coil terminals, reduction of capacity and eventual failure or burn out. In such a coil that is manufactured to just barely meet specifications, even a small reduction of capacity may be enough to cause it to fail to accomplish the purpose it was intended for. An electronic coil that is hot to the touch IS NOT a normal condition. It WILL fail prematurely. Either return the unit to the manufacturer or be ready to replace it soon.
- posted
17 years ago