MZ11-06A300-600RM (MZB6 30-60 Ohm) PTC Thermistor 485 232 Communication Interface Protection Resistor

MZB-6 30-60Ω Ohm (MZ11-06A300-600RM) PTC Thermistor 485 232 For Communication Interface Protection

1.Description

One of the properties of PTC thermistors is that when an excessively large current flows, they generate heat by themselves and become highly resistive. With this property, they are used as overcurrent protection devices.

2.Advantages of PTC thermistors

PTC thermistors are temperature-dependent resistors based on special semiconductor ceramics with a high positive temperature coefficient (PTC). They exhibit relatively low resistance values at room temperature. When a current flows through a PTC the heat generated raises the temperature of the PTC. Once a certain temperature (Curie temperature) is exceeded, the resistance of a PTC rises significantly. This effect can be used to protect circuits or devices against overcurrents. In this case, the overcurrent brings the PTC to a high temperature and the resulting high resistance then limits the overcurrent. When the cause for malfunction is eliminated the PTC will cool down and act again as a resettable fuse. With this property, PC thermistors are used as overcurrent protection devices. The following exemplary applications describe how PTC thermistors can be used for overcurrent protection.

3.Purposes

« For inrush current limiting »

« For overcurrent protection »

« For telecom »

Inrush current limiting for on-board chargers (OBC)

Inrush current limiting for industrial inverters

Overcurrent protection for on-board DC motors

Overcurrent protection for solenoids

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

4.Specifications of Appearance

5.Dimensions (mm)

6.Electric Performance

7. Series Specification

7.1 Select PTC thermistor as an overcurrent heat protection element for overcurrent protection. First of all, confirm that the maximum normal working current (that is, the non -action current of PTC thermistor for overcurrent protection) and the installation position of PTC thermal resistance (PTC thermal resistance ( At the time of normal work), the highest ambient temperature, followed by the protection current (that is, the action current of PTC thermistor with PTC), the maximum working voltage, the rated zero power resistance, and the shape size of the component. As shown in the figure below: the relationship between the environmental temperature, the non -action current and the action current.

7.2 Application principle

When the circuit is in a normal state, the current of the PTC thermistor with PTC is less than the rated current by overcurrent protection. PTC thermistor is in normal state, and the resistance value is small, which will not affect the normal operation of the protected circuit. When the circuit fails and the current exceeds the rated current, the heating resistance of PTC for overcurrent protection is suddenly heated, which is high -resistant, which makes the circuit in a relatively "disconnect" state, thereby protecting the circuit from damaging. When the failure is eliminated, the PTC thermistor is also automatically responded to the low -resistance state, and the circuit is restored to normal work.

The picture above is a diagram of the Fu-Ante curve and load curve of the circuit when working normally. From point A to point B, the voltage applied to PTC thermist resistance gradually increases, and the current flowing through the PTC thermistor is also linear. It indicates that the resistance value of the PTC thermistor is basically unchanged, that is, keep at a low -resistant state; from point B to point E, the voltage gradually increases, and the PTC thermistor is increased rapidly due to the heating resistance. The rapid decrease in the current indicates that the PTC thermistor enters the protection state. The normal load curve is lower than point B, and the PTC thermal resistance will not enter the protection state.

Generally speaking, there are three types of overcurrent and heat protection:

1. current overcurrent (Figure 3): RL1 is the load curve during normal working. When the load resistance value is reduced, such as the transformer line is short -circuited, the load curve changes from RL1 to RL2, exceeding B,ptc thermistor go into protection state;

2.Voltage overcurrent (Figure 4): The power supply voltage increases. For example, the 220V power cable suddenly rises to 380V, and the load curve changes from RL1 to RL2, exceeding point B, and PTC thermistor to enter the protection state;

3,Temperature overheating (Figure 5): When the ambient temperature rises exceeds a certain limit, the PTC thermistor V-I curve has changed from A-B-E to A-B1-F, the load curve RL exceeds B1 points, and PTC thermistor to enter the protection state;

Overcurrent protection circuit diagram

Precautions

1. Welding

When welding, it should be noted that the PTC thermistor cannot be damaged due to excessive heating. The highest temperature, the longest time and the shortest distance must be observed below:

Welding soldering iron welding

The temperature of the molten pond MAX*.260 ℃ max*.360 ℃

*Welding time Max*.10s max*.5s

The smallest distance from the PTC thermistor is min.6mm min.6mm

Under worst welding conditions, it will cause changes in resistance.

2. Coating and irrigation

When coating and irrigation are added to the PTC thermistor, mechanical stress is not allowed to appear due to different thermal expansion in solidification and subsequent treatment. Please use irrigation materials or fillers carefully. The upper limit temperature of the PTC thermistor is not allowed during curing. In addition, it should be noted that irrigation materials must be chemical neutral. The restoration of titanate ceramics in PTC thermistor may cause reduced resistance and loss of electrical performance; changes in thermal heat dissipation conditions due to irrigation may cause local overheating on PTC thermistor, which causes it destruction.

3. Clean

Freon, methane or vitaminyl chloride and other mild cleaning agents are suitable for cleaning. It can also use ultrasonic waves, but some cleaning agents may damage the performance of thermistor. It is best to test it before cleaning or consult our company.

4. Storage conditions and duration

If the storage period is properly stored, there is no time limit for the storage period of the PTC thermistor. In order to maintain the weldability of the PTC thermistor, it should be stored in an atmosphere without erosive. At the same time, pay attention to air humidity, temperature and container materials. The original should be stored in the original packaging as much as possible. The touch of the metal coverage layer of the unwalked PTC thermistor may cause a reduced weldable performance. At the exposure of overcorders or over -high temperatures, the performance of some specifications of products may change, such as weldability of tin lead, but it can be stored for a long time under normal electrical component preservation conditions.

5. Precautions

In order to avoid accidents/short circuit/burning such as PTC thermistor, when using (test) PTC thermistor, you should pay special attention to the following matters: Do not use it in oil or in water or flammable gas, (test) PTC thermistor; do not use (test) PTC thermistor resistor under the condition that exceeds the "maximum working current" or "maximum working voltage" conditions.

6.MOUNTING

PTC thermistors can be mounted by wave, reflow, or hand-soldering. Current levels have been determined according IEC 60738 conditions. Different ways of mounting or connecting the thermistors can influence their thermal and electrical behavior. Standard operation is in still air, any potting or encapsulation of PTC thermistors is not recommended and will change its operating characteristics.

Typical Soldering

235 °C; duration: 5 s (Lead (Pb)-bearing)

245 °C, duration: 5 s (Lead (Pb)-free)

Resistance to Soldering Heat

260 °C, duration: 10 s max.

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