一.概述
HLMZ2系列PTC熱敏電阻是一種自動保護、自動恢復使用、無觸點、無噪音、無火花的“萬次保險絲”，或稱“自恢復保險絲”，是繼“溫度保險絲”和“溫度開關”之后推出的第三代保護器件。適用于萬用表、充電器、小型變壓器、智能電度表、數字萬用表、微電機、小型電子儀器等線路中做過流、過熱保護。
二、應用實例及外形圖
應用原理如下圖所示：把PTCR串聯在負載電路中，當電路處于正常工作狀態時，通過PTCR的電流不超過額定電流即不超過PTCR的*大不動作電流，PTCR處于常態，阻值較小，不會影響被保護電路的正常工作。當電路出現故障，電流大大超過額定電流，PTCR驟然發熱，呈高阻態，使電路處于相對“斷開”狀態，達到保護目的。當故障排除后，PTCR自動恢復正常工作。
三、產品編號
備注：
1. 除上表所列規格型號之外，可按用戶要求設計生產其它規格要求的PTC熱敏電阻器。
2.HLMZ2系列PTC熱敏電阻已取得關于ROHS限制的六種有毒、有害物質含量的SGS測試報告。
五、應用實例
實例I
HLMZ2-6 20Ω型PTC熱敏電阻是華龍公司從程控交換機用程控保安單元中演變出來的一種應用于485通信接口的保護元器件。該產品串接在485通信接口中，可有效防止通信線路因意外破損或人為損害而導入的220V市電對該接口的損壞，也可適當降低雷電感應通信線路對該接口的影響。該產品具有穩態阻值小、額定電流低、耐壓能力高、響應速度快等特點，是485通信接口實現保護的經濟適用的選擇。
應用電路
PTC Thermistors for Restricting Overloading and Current
Main Categories
According to the appearance, the PTC Thermistors for restricting overloading and current can be divided into some categories, such as porcelains, shellies, wrapping and pasters.
Working Theories
The restricting overloading protection PTC Thermistor is connected in series in the overloading circuit. when the circuit is in the normal working state , the current flowing through the PTC Thermistor is not high enough to make the temperature exceed the Curie temperature for protection ,and it is always in the low state of resistance. When the circuit breaks down and the return circuit current increases, the resistance of restricting overloading protection PTC Thermistor goes up sharply for being warm, until the circuit is cut off. After the clearing of the circuit trouble, the PTC Thermistor begins to cool and come back to the state of low resistance, and then the circuit enters normal working condition. When the circuit breaks down next time, the PTC Thermistor can enter the state of protection again.
Applications
Restricting overloading protection PTC Thermistor is mainly used in the remote alternating machinery, remote control telephones, distributing frames, safe-guard units, voltage transformers, crystal conductors, automats, cars, washing-machines, fluorescence lamps, computer peripheral equipments, motor starters, household appliances, electronic instruments and micro power equipments at present.
Advantages
Compared with the traditional fusing filament, the restricting overloading protection PTC Thermistor reacts fast, contactless, flameless, noiseless and recoverable. Meanwhile, compared with the organic high molecule PTC Thermistor, the pottery restricting current PTC Thermistor of normal temperature changes little after numerous protection with a better performance of withstanding voltage. Additionally, it can resume steadily and has a good performance. If hotly-coupling installed with overloading, it can repair the circuit trouble caused by the double effects of overheating and overcurrent. |
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