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Low voltage fuse selection guide
  Time:2017-05-28   Source:上海智广熔断器有限公司!  

Fuse body set up main function is in the circuit failure occurs when the circuit can cut off safely and reliably, thus providing protection for the discrete components or the entire circuit. The following for the user

Choose fuse body need to consider about the conditions:


The normal working conditions and installation conditions

Ambient air temperature: - 5 ℃ ~ + 40 ℃, and its within 24 h of average temperature does not exceed + 35 ℃

Altitude: not more than 2000 m

Atmospheric conditions: humidity: installation site of air relative humidity when the highest temperature is + 40 ℃ not more than 50%, at low temperature can be allowed to have higher relative humidity. For example,

At 20 ℃, relative humidity of 90%, due to temperature change in any condensation on the product must be taken。

Pollution levels: level 3

Install categories: class III


The environment temperature

Refers to the direct fuse body surrounding air temperature, should not be confused with room temperature. In many practical situations, the fuse body temperature is high, this is because the fuse body is configured in different

Structure of support/base and the fuse is closed in the power distribution/control cabinet.

Reduced capacity to use

At 20 ℃ environment temperature, we recommend the actual working current of fuse body should not exceed the rated current value. When choosing the fuse body should take into account the environmental and working conditions, such as degree of closed, air flow, connecting cable size (length, cross section), the change of the respect such as the instantaneous peak value; Current of fuse body bearing capacity test was conducted in 20 ℃ environment temperature, the actual use is influenced by environmental temperature change. Environment temperature is higher, the higher the working temperature of fuse body, its life is shorter. Run at low temperatures, on the other hand, will prolong the life of the fuse body.


Said below on the impact of environmental temperature on current carrying capacity of typical curve

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misoperation

Misoperation is often because of the designed circuit analysis due to incomplete. In the "choose fuse body should consider the factors of", must pay special attention to one of the three, 1), 3), and 6) the normal working current, environment temperature and overload increment. Misoperation caused by conventional runtime, for example, is a common cause of failed to fully consider such as motor starting current of circuit, surge current and harmonic current of capacitor loop as well as the air around the fuse body temperature, etc.

The rated breaking capacity

Is the fuse body can be reliably under rated voltage fuse maximum short-circuit current. Short circuit when the fuse in the body will pass is much bigger than the normal working of instantaneous current, safe operation

For fusing body intact state (not burst) cut off the circuit. This company fuse body rated breaking capacity to 120 ka. Reliable current limiting characteristics make electrical wiring of the equipment from the damaging electric power.

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The fuse body supporting pieces (fuse)

In many practical occasions, fuse body installed on the fuse body support/base, they can not be used as a switch - not to connect or cut off the load.

Select the fuse body should consider various factors:

1. The normal working current,

2. Working voltage;

3. The environment temperature;

4. The overload current and the fuse body must fuse time;

Possible fault current; 5.

6. Pulse, impact current and surge current, harmonic current, starting current and circuit transient process of value;

7. The structure size, connection mode, visual indication (fuse or not), etc.

Motor short circuit protection (aM) by fusing body:

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