What are the different types of resettable ptc fuse?
2024-05-31
  • There are two main types of self-healing fuses: ceramic PTC and polymer PTC, each with different characteristics that make it suitable for different applications. The selection of a specific type of fuse depends on the requirements of the application. Both types of PTC self resetting fuses have PTC resistance.

    Ceramic PTC fuses are commonly used in high current applications. Ceramic PTC fuses are made of ceramic materials, with high current capacity and low resistance value. Polymer PTC is mainly used for low current applications. Polymer fuses are typically smaller and have faster response times.


  • Self recovery fuses come in different external dimensions and installation options, including battery strips, radial leads, and surface mounting.

    Axial lead battery with PTC

    Axial lead batteries with PTC are used for rechargeable and lithium-ion battery packs to provide overcurrent protection. Beluse's 0ZSC series can manage any current from 1.2 to 4.2A and operate at any voltage from 15 to 30 VDC.

    Surface mounted PTC

    OXCG series surface mount PPTC

    Surface mounted self-healing fuses are highly valuable for consumer electronics and other space applications. They are directly installed on the circuit board without the need for drilling holes on the board.

    Radial lead PTC

    0ZRS series radial lead PPTC

    The radial lead of PTC extends radially from the main body of the equipment. They have multiple sizes and resistance values to choose from.

    What are the specifications of reset fuse?

    1. Maintain current: The maximum amount of current that a self restoring fuse can withstand before tripping and transitioning from a low resistance state to a high resistance state. The holding current of the fuse is higher than the maximum current in the circuit, so it will not trip during normal operation.

    2. Tripping current: The amount of current that causes the fuse to trip and disconnect the circuit. Self restoring fuses have a higher tripping current than traditional fuses, and they are designed to quickly trip in response to overcurrent conditions. The tripping current usually exceeds the holding current.

    3. Rated voltage: The maximum voltage at which a fuse can operate safely without breakdown. The rated voltage of the selected fuse must match or exceed the circuit voltage used.

    4. Maximum current: The maximum amount of electricity that can pass through a fuse, exceeding this current can cause the fuse to overheat and potentially cause damage. The maximum rated current is usually specified by the thermistor manufacturer and is based on the size, material, and design of the thermistor.

    5. Maximum Trip Time (MTT): The maximum time required for the device to switch from low resistance to high resistance when a fault current occurs. The tripping time of PPTC devices is defined as the time required to trip the device when a fault current occurs. The time depends on the magnitude and duration of the fault current, as well as the ambient temperature.

    6. Typical power: The amount of power typically consumed when a fuse is in a tripped state in a still air environment at 23 ° C.

  • What is a self recovery resetting a fuse?

    The self recovery fuse is made of responsive conductive polymer, which has thermal responsiveness and conducts electricity under normal conditions. However, under overcurrent conditions, the polymer will prevent the flow of current. This polymer is mixed with other materials such as polyethylene, polycarbonate, and carbon black to achieve the correct balance of thermal, mechanical, and electrical properties.

    Where is the resettable fuse fuse used?

    PPTC devices are commonly used in various electronic and electrical applications that require protection against overcurrent conditions. Some common applications of self restoring fuses include consumer electronics, power supplies, telecommunications equipment, and industrial control systems. In addition to these applications, self-healing fuses are also used in various other automotive systems, such as power distribution devices, starter motors, and battery management systems, to provide overcurrent protection.

    What is the difference between self-healing fuses and traditional fuses?

    The function of PPTC and fuse is the same: to protect electronic circuits from overcurrent related issues. The difference is that the fuse must be replaced after tripping, while PPTC can reset itself. PPTC can handle sudden overcurrent without the need for replacement.

    Both PPTC and fuses react to excessive current by generating heat, but their ways of action are different. The fuse blows, completely interrupting the current, while PPTC limits the current by changing from a low resistance state to a high resistance state as the temperature increases. In short, if it is necessary to prevent the flow of current to fully protect the device, a fuse is preferred. On the other hand, PPTC is typically used in situations where frequent overcurrent events are expected to occur, and it is crucial to maintain stable system uptime at lower service costs. They are also useful in challenging remote or difficult to reach locations for replacing fuses.

  • one newly overcurrent protection component is an overcurrent electronic protection element, which is made of high molecular organic polymer under the conditions of high pressure, high temperature and vulcanization reaction, mixed with conductive particle material and processed by special process. The traditional fuse overcurrent protection can only protect once and needs to be replaced if it is burnt out. The self-healing fuse has the dual functions of overcurrent thermal protection and automatic recovery.

    Application of polymeric positive temperature coefficient device (PPTC)

    Ballast

    Automobile self-recoverable Fuse,Fluorescent lamps need a ballast to generate high voltage and high current. The ballast controls the electrical characteristics of the fluorescent lamp.

    When the lamp is turned on, the electronic ballast generates a high-voltage impact at both ends of the lamp to make the lamp light, and a self oscillation circuit is formed in the electronic ballast, which is controlled by a transistor.

    Many electronic ballasts fail because of the lamp. When the lamp is short circuited, reaches its service life, or the lamp is taken off, overcurrent will occur, resulting in open circuit of the cathode of the lamp.

    The load resistance becomes low due to the power factor. During starting, the ballast works more than three times under abnormal working current and high oscillation frequency; The switching circuit generates overcurrent, which leads to the failure of the ballast.

    The self recovery fuse can provide the protection of the lamp when it reaches the service life and the fault protection of the transistor.

    Because the ballast often fails because the upper and lower voltage switches of the transistor are opened at the same time, the fault protection of the transistor is of great significance.

    Firstly, a passive electronic component has the performance of automatic recovery, which can reduce the number of product repair and service, so as to reduce the cost.

    Secondly, because Auto-recoverable Fuse can act in a very short time to protect some sensitive resistors in the circuit, the reliability and service life of the ballast can be improved.

    Third, the power consumption of self resetting fuse is very low, and it will not consume energy due to extreme heating under normal current working state. Under normal operating current, the resistance value is very small (usually only a few tenths of a Ohm), so no oscillation circuit will be formed.

    Fourth, PTC Resettable Fuses has small volume and occupies small space on the circuit board, which is convenient for design.


    Transformer

    The fault of power supply equipment with transformer is mainly caused by overcurrent, which is usually caused by circuit short circuit or load reduction; In case of failure, the circuit will smoke and catch fire, so as to damage the circuit and interface.

    The transformer of the lamp body of low-voltage halide lamp structure often fails due to short circuit.

    If the installation and connection between the transformer and the lamp body are improper, it is easier to be damaged.

    Because the lamps are used in parallel, the current is particularly large in case of short circuit.

    Installing the self resetting fuse on the second coil of the transformer can prevent short circuit and overload faults.


    Horn

    The horn system has strict protection requirements.

    The ordinary fuse only plays a one-time protective role in the horn, which increases the repair rate of the product; In addition, additional fuse boxes and wires increase the manufacturer's cost. In addition, the fuse used must also meet the specifications. A fuse of the wrong specification will damage the horn.

    Installing circuit breaker is also a solution; However, before they are disconnected, they will make noise when they begin to disconnect.

    Therefore, the best choice is self restoring fuse and self restoring fuse element.

    The self resetting fuse is equivalent to a soft switch in the off state (high resistance state). When the fault is eliminated, it will automatically return to the state of low resistance path.


    Battery

    a. Mobile phone battery pack:

    The key to the cell phone battery pack is its own application characteristics. This kind of battery is installed in a small, light and narrow box.

    NiCd, NiMH and Li ion, the three main chemical batteries, are all packed in this universal box.

    Generally, the working voltage of the battery pack is less than 10V, and the maximum charging voltage is 16V. The working voltage of the latest battery pack is even lower, between 3 ~ 4V.

    This means that the packaging of the battery pack changes very quickly, from the welded strip to the mounting components on the printed circuit board.

    Battery packs need circuit protection devices, such as vtp210g, which can maintain the current at about 1 ampere at 60C.

    The lower the resistance of the protection circuit, the smaller the energy loss and the larger the space for component selection.

    b. Cordless telephone battery: the current and voltage of cordless telephone are relatively small. Srp120, ltp070 and ltp100 are good overcurrent protection elements.

    c. Radio communication battery: the current of radio communication credit is greater than that of mobile phone battery and less than that of laptop. LR4 series has a working current of 7.3 amps, small volume and light weight, which is very suitable for this application. SRP or LTP series with large operating current can also be applied.


    Chemical battery

    Chemical batteries are more and more widely used. The application of these components will make the battery pack have a better and lower cost protection device.

    A. NiCd battery:

    NiCd batteries with low impedance and stable chemical properties are not as sensitive to overcurrent as NIMH and Li ion batteries.

    However, due to low loss, it is still widely used. However, in short-circuit or overcurrent states, their low internal resistance will lead to higher current flow.

    Generally, the failure cause of these batteries is overcurrent rather than overheating, which is applicable to products applied by any battery material.

    B. NiMH battery:

    NiMH battery has higher energy density than NiCd battery.

    When it exceeds 90C, these batteries are more prone to degradation.

    VTP or LTP is more suitable for protecting this kind of battery than SRP / LR4 material.

    According to the battery design method, SRP and LR4 can protect the battery, but LTP and VTP have stronger thermal conductivity.

    C. Li ion battery:

    Among all chemical batteries, Li ion battery has the highest energy density and the most sensitive chemical characteristics.

    Circuit protection device shall be installed during use and charging.

    The general protection device is an integrated circuit, but this is not the safest, because the integrated circuit itself may also cause short circuit or CMOS startup failure, making the protection device unsafe.

    When it exceeds 90C, Li ion battery will also begin to degrade. Since the voltage of this battery is the largest, the requirements for circuit protection are more stringent.

    Although LTP, SRP and other series have been used in the battery for a long time, the most suitable PTC element is VTP; For high-capacity Li ion batteries, the action time of LR4 series is shorter and more suitable than SRP series.

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