250V 270 OHM Positive Temperature Coefficient Resistor MZ21 PTC Thermal Resistor

Overcurrent Protection PTC Thermistor MZ21 250V 60mA 27R For Communication Equipment

I Description Of The Overcurrent Protection PTC Thermistor MZ21

MZ11 series PTC thermistors are used instead of conventional fuses to protect loads such as multimeter, transformers, intelligence-ammeter, and digital multimeter, etc. or electronic circuits against overcurrent, which is the third protective devices after "temperature fuse" and "temperature switch". They are also called "auto restore fuses" or "ten-thousand-time fuses".

II OPERATING PRINCIPLE OF THE Of The Overcurrent Protection PTC Thermistor MZ21

The operating principle is showed in the following figures, the PTC thermistor fuse connected in series with the load. When a circuit is in normal status, the current through PTC is no exceed the rated current and in normal state PTCR keep low resistance, which will not affect the normal operation of the protected circuit. In case of any trouble in the circuit and the current is greater than the rated value, the PTCR will become hot quickly and present as a high resistance state, which sets the circuit relatively "off" to protect the circuit from damage. After the trouble is removed, PTCR will automatically restore its low resistance state and the circuit will resume normal operation.

III Dimension Of The Overcurrent Protection PTC Thermistor MZ21 (mm)

IV Applications of PTC thermistors for telecom overcurrent protection

Application: Overcurrent protection in a surge protective device (SPD) used for security systems

PTC thermistors for telecom applications are also used for various security systems in factories and office buildings. For example, surge protective devices (SPD) are installed at important locations in these systems because signal cables used for fire alarm systems, surveillance camera systems, and other network systems that connect multiple sites can be damaged by lightning surges.
The diagram below shows an example of a protection circuit that uses a replaceable plug-in SPD. The plug side includes an arrestor and a varistor for overvoltage protection. The socket side includes a PTC thermistor for overcurrent protection.
TDK offers a comprehensive lineup of PTC thermistors for telecom applications. Telecom pair protectors (TPP), each of which incorporates two PTC thermistors packaged in a plastic case, are often used for SPDs.
The function of the PTC is very similar to that described in the previous section.

Figure 5 Example of a protection circuit for plug-in surge protection device (SPD)

Dongguan Ampfort Electronics Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales, committed to becoming a comprehensive supplier of circuit protection components.

We introduced advanced quality system,management systems and high-precision automation equipment from Germany, set up multiple production bases and continue to increase product lines. Our team consist of experienced engineers, passionate business elites, and regularly trained skilled workers, which provides a solid foundation for quality assurance and productivity performance. Moreover, our products have passed safety certifications of many countries and are favored by many consumers by years’ unremitting efforts.

We cooperated with universities and colleges, and will continue to research and develop new products , committed to high-quality circuit protection solutions, and provide global customers with efficient technology, products, and testing support to meet their requirements for rapid development of new products. We are gradually updating from "Made In China" to "Created In China" and to "Intelligent Manufacturing In China", from circuit design to product testing, we will provide you with one-stop service in the field of circuit protection.After years of intensive cultivation, we have maintained a good relationship with our peers and have become distributor of many famous electronic component brands to meet the diverse needs of customers.

The main products include: Thermistors, Varistors, Temperature Sensors, Fuses and corresponding Hardware and Plastic accessories, Inductors, Thermal Protector, Overload/Composite Protectors, Discharge Tubes, Photoresistors and Wiring Harnesses etc. Through the combination of different process devices,Ampfort Electronics can meet customers' individual circuit protection requirements. Our products are widely used in: power adapters, switching power supplies, chargers, transformers, computers, telephones, household appliances, communication products, lighting products, toy products, various instruments and various electronic cables, electrical products, IT, Consumer electronics, automobiles, batteries and other fields.

Choose us, Ampfort will be your loyal and reliable partner for protection circuit products !

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