一.概述
HLMZ2系列PTC热敏电阻是一种自动保护、自动恢复使用、无触点、无噪音、无火花的“万次保险丝”，或称“自恢复保险丝”，是继“温度保险丝”和“温度开关”之后推出的第三代保护器件。适用于万用表、充电器、小型变压器、智能电度表、数字万用表、微电机、小型电子仪器等线路中做过流、过热保护。
二、应用实例及外形图
应用原理如下图所示：把PTCR串联在负载电路中，当电路处于正常工作状态时，通过PTCR的电流不超过额定电流即不超过PTCR的zui大不动作电流，PTCR处于常态，阻值较小，不会影响被保护电路的正常工作。当电路出现故障，电流大大超过额定电流，PTCR骤然发热，呈高阻态，使电路处于相对“断开”状态，达到保护目的。当故障排除后，PTCR自动恢复正常工作。
三、产品编号
备注：
1. 除上表所列规格型号之外，可按用户要求设计生产其它规格要求的PTC热敏电阻器。
2.HLMZ2系列PTC热敏电阻已取得关于ROHS限制的六种有毒、有害物质含量的SGS测试报告。
五、应用实例
实例I
HLMZ2-6 20Ω型PTC热敏电阻是华龙公司从程控交换机用程控保安单元中演变出来的一种应用于485通信接口的保护元器件。该产品串接在485通信接口中，可有效防止通信线路因意外破损或人为损害而导入的220V市电对该接口的损坏，也可适当降低雷电感应通信线路对该接口的影响。该产品具有稳态阻值小、额定电流低、耐压能力高、响应速度快等特点，是485通信接口实现保护的经济适用的选择。
应用电路
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 ephones, 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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