Traditional AC filter should be a very reliable appliances, but also often occur using coil burned out, contact bonding, core hair ring. Aiming for domestic use have reached IEC standard products, there can not work reliably, analyzed, and presented by the expansion of the coil operating voltage range of methods, highly reliable design of the AC filter, and Introduction to its design point. Keywords Wide voltage conventional filter highly reliable filter coil burned in use often occurs, contact bonding, core hair ring (three chronic disease). There are reasons for the product itself causes, there are reasons for the use and power supply areas. How to improve the design and manufacture of conventional filters, larger grid voltage range to meet, still work reliably it is the purpose discussed herein. In order to design and manufacture high-quality filter, you must first figure out ways to generate three reasons for the failure of traditional filters and resolved.
   1. Core hair ring:
   The reason is the current zero AC solenoids, reducing suction to less than the reaction force is not strong core pull, when the core pole face is not level, it will generate noise, which is the core hair ring. Rattling the iron at the factory is not the factory, although standard distance of 1m, the noise not exceed 40 decibels, but the factory standard is often judged by artificial feel, more than "micro-Ma" on the sentence failed, currently feel is qualified by the core measure, it should be said that the more stringent. Certainly not a scientific standard, but high ambient noise in the workshop, using decibel meter test identification methods are also inconvenient. When the hand appears differences and have samples stored in advance as a criterion. In the production plant to reduce noise method, the core riveted, polished, can meet the requirements. In the case of use, noise occurs stop using roughly:
    1) polar dirt (such as iron rust, oil dirt);
    2) magnetic break points;
    3) a foreign body falls pole face (such as fine solid particles) which will cause the core to produce a strong noise.
    2. Coil burned many reasons:
    2.1 design margin is not enough:
    2.1.1 enameled improper selection: To reduce costs, use wire temperature below 130 ℃. Even the choice of oil enameled wire.
    2.1.2 Coil temperature: general requirements designed 60K or less, and high strength polyester enameled heat is generally used in 155 ℃, some designers to reduce the number of turns in order to reduce costs, improve coil temperature rises and some even up to 70K ~ 80K 90K, the coil wire is under long-term high temperature, reducing the coil insulation strength.
    2.1.3 suction reaction force with no intact: the voltage is low, pull hard, long operation time, coil withstand high current starting time increases, more heat resistance of the coil increases, and driven more evident lack of suction, pull more difficulties can not pull up. Hollow reactor coil at work, the coil current is large it will soon burn out.
    2.1.4 Product operating voltage range is not wide enough, the voltage is lower than 85% may occur can not pull hot, voltage higher than 110%, the coil overheating burn.
    2.2 strict production process control or out of control:
    2.2.1 strict incoming inspection: enameled film uneven, bare wires exposed local excessive pinholes.
    2.2.2 coil winding flawed process, without undue tension control or control; coiled, the control winding tension is to ensure that the coil is wound not to be too loose, not too tight, so that wire stretched, resulting in dielectric strength is reduced.
    2.3 Use of related issues:
    2.3.1 control coil power: When powered by a transformer, the transformer output voltage less than the rated voltage Us required value; voltage is too high than the standard requirements.
    2.3.2 control coil voltage optional: Us have 380V, 220V, 110V until 12V are available, the general principle of choice: a, Us not too high, can not choose 110V 380V, because the high voltage turns more will produce a high breaking overvoltage damage the coil insulation, high voltage coils, enameled more carefully, when fine enameled wire tension control a slight deviation between the coils generating layer will reduce inter-turn insulation strength . b, Us also should not be too low, can not choose 12V 48V, because when the voltage is below 20V, contact connected to the contact sometimes unreliable. Low voltage diameter thick, thinner wire will not stretch, but too thick diameter not easy around the system, especially the large-capacity (250A) over the filter, it is best not to choose a value lower than the voltage of 110V Us .