What is the difference between DC fuse and DC circuit breaker, and how to choose?

Low-voltage fuse and circuit breaker are commonly used electrical equipment in box-type substation, due to the power supply content of the DC system of the substation, the circuit distribution is wide, there are often many branches in a DC network that need to be set up circuit breaker or fuse for protection, in the DC circuit, the fuse and circuit breaker are the main protection components of the DC system for the overcurrent and short-circuit faults of each outgoing line, which can be used as the feeder loop power supply network disconnection and isolation, and the protection performance and other characteristics of the DC fuse and DC circuit breaker are compared.

The DC fuse has good selectivity. As long as the rated current of the fuse of the upper and lower fuses meets the requirements of the overcurrent selection ratio specified in the national standard and IEC standards: 1, that is, the rated current of the upper fuse is not less than the times of the value of the lower level, it is deemed that the upper and lower levels can selectively cut off the fault current; Moreover, the DC fuse has good current limiting characteristics and high breaking capacity; Relatively small size; And it's cheaper.

For details, please refer to it.

First of all, a fuse and a circuit breaker are different things.

Fuse, also known as: fuse, fuse, etc., is a kind of one-time protection product that relies on overcurrent fuse to achieve the purpose of protection. The structure of the fuse is mainly divided into melt, melt core and quartz sand.

Circuit breaker, also known as switch, is a switching circuit device with arc extinguishing function that can be used repeatedly. The structure of the circuit breaker is complex, which is divided into manual control and automatic control, and will automatically trip when the setting current is reached.

Fuses and circuit breakers are strictly divided into AC and DC. Because DC arcs are difficult to extinguish, fuses and circuit breakers used in DC systems are more powerful than AC arc extinguishing functions.

As for the question of how you say to choose, it depends on the specific situation, and cannot be generalized.

The DC fuse is mainly composed of melt and melt pipe and external filler. When in use, the fuse is connected in series in the protected circuit, and when the current of the protected circuit exceeds the specified value, and after a certain period of time, the heat generated by the melt itself blows the melt to disconnect the circuit, so as to play the role of protection.

A DC circuit breaker (DC circuit breaker) is a switching device used to distribute electrical energy and protect circuits and power supply equipment from overload, short circuit and other faults.

From the above definition, the DC melter is a one-time protection component, which is generally used for circuit short-circuit and over-current protection after the failure of the post-level protection circuit. Circuit breakers, on the other hand, have multiple use capabilities, but there are contacts and related components in them, which may cause protection failure due to part failure or contact burning. Both have their own advantages and disadvantages, generally speaking, the dissolver is used for the most advanced stage, which is the first level of protection, and its role is to protect the circuit breaker after failure.

The cut-off is used for the primary protection of direct electrical appliances and is the primary protection device.

What they have in common: Both are circuit protection appliances that are used to protect circuit breakers from overload and short circuits.

Difference 1: The protection mode of the circuit breaker is tripping, and the power supply can be restored by closing after troubleshooting, which is convenient;

The protection mode of the fuse is fuse, and the melt needs to be replaced to restore the power supply after troubleshooting, which is inconvenient.

Difference 2: The tripping speed of the circuit breaker is millisecond (ms), which is relatively slow, and is not suitable for some occasions with high requirements for truncation speed;

The fuse speed is in the microsecond (s) range, which is much faster than that of the circuit breaker, and is suitable for occasions with fast truncation requirements.

There are many other differences, but the simpler and most important ones are these two.

Then let's understand the difference between a fuse and a circuit breaker. Introduction to the difference between fuses and circuit breakers They are functionally the same, both are used to cut off the circuit, but the working principle is different. The fuse works according to the thermal effect of the electric current.

When the current exceeds a fixed value, the fuse in the fuse will heat up and fuse, so as to realize the segmented circuit, protect the equipment from being burned out by the high current, and replace the fuse in the fuse every time the fuse is broken. Introduction to the difference between fuse and circuit breaker Due to the different types of circuit breakers, the principles are different, but generally due to excessive current, which leads to the excitation of the tripped coil, that is, the circuit breaker trips. Of course, it is also possible to manually control the opening and closing of the short-circuit breaker.

Well, that's the end of today's introduction. From the article introduced above, we can see that although these two parts have the same effect, there are essential differences. I hope today's introduction will be helpful to you.

DC fuse and AC fuse both belong to the category of current-limiting fuses, the shape and structure are very similar, but the current breaking process is very different: AC power is conducted alternately in a sinusoidal waveform, and the weekly wave has a zero-crossing point, and the lowest power value at this time is easy to extinguish the arc; However, there is no zero-crossing point in any waveform of direct current, and when the DC short-circuit fault current is interrupted, the arc is forced to be extinguished by the rapid vaporization of the fuse and the diffusion, adsorption and cooling of quartz sand, so it is much more difficult than breaking the AC arc.

DC fast fuse can replace AC fast fuse, not vice versa.

The so-called fast melting is nothing more than requiring the fuse to be blown within a certain period of time. So what is the difference between AC and DC in fusing (thermal effect)? That's a matter of communicating the RMS. RMS for AC = RMS for DC, now you know.

As you can see from the name: AC fuses are used for alternating current, and DC fuses are used for direct current.

DC fuse and AC fuse both belong to the category of current-limiting fuses, the shape and structure are very similar, but the current breaking process is very different: AC power is conducted alternately in a sinusoidal waveform, and the weekly wave has a zero-crossing point, and the lowest power value at this time is easy to extinguish the arc; However, there is no zero-crossing point in any waveform of direct current, and when the DC short-circuit fault current is interrupted, the arc is forced to be extinguished by the rapid vaporization of the fuse and the diffusion, adsorption and cooling of quartz sand, so it is much more difficult than breaking the AC arc.

DC fast fuse can replace AC fast fuse, not vice versa.

The DC one can replace the AC one, and the AC one cannot replace the DC one. The two work on different principles, and the arc extinguishing performance of DC is higher. Another, if you want to switch, take a closer look at whether the voltage level is consistent. Generally, the DC voltage is low.

The role of the circuit breaker:

The function of the circuit breaker is to cut off and turn on the load circuit, as well as cut off the fault circuit, to prevent the expansion of the accident and ensure safe operation.

The role of the fuse:

The function of the fuse is to act as a melt, when the current is too high or exceeds the load current through the fuse itself to prevent the electrical components of the circuit from being damaged, this is two differences from the circuit breaker breaking current, its role can be understood by the fuse commonly used in our home, and the circuit breaker is basically used as the main switch. Whereas, the fuse is installed in the circuit. Does this explain it clearly?

The fuse is fused, which will blow and then protect the load, and the circuit breaker is circuit breaker protection, the so-called tripping.

The fuse is a fuse or the like, which plays the role of insurance, and it needs to be replaced with a new one after a one-time fuse. And the circuit breaker is the switch. Used to shut down the power supply.

The fuse is 88 at a time, it is burned out, the circuit breaker will not break, it is made with the principle of different metal thermal expansion indexes, and it can be used again after cooling, or it can be broken back manually.

1.The main features of the fuse include:

1) Good selectivity. As long as the rated current of the fuse of the upper and lower fuses meets the requirements of the overcurrent selection ratio specified in the national standard and IEC standards: 1, that is, the rated current of the upper fuse is not less than the times of the value of the lower level, it is deemed that the upper and lower levels can selectively cut off the fault current;

2) Good current limiting characteristics and high breaking capacity;

3) Relatively small size;

4) **Cheaper.

2.The main features of the fuse:

1) The fuse must be replaced after the fault fuse;

2) The protection function is single, only a period of overcurrent inverse time characteristics, overload, short circuit and ground fault are used for this protection;

3) When a phase fuse occurs, the three-phase motor will lead to the adverse consequences of two-phase operation, of course, it can be compensated by a fuse with an alarm signal, and the three-phase fuse can be disconnected by one-phase fuse;

4) Remote control cannot be realized, and it needs to be combined with electric knife switch and switch to be possible.

3.The fuse and the circuit breaker have the same thing: they can both achieve short-circuit protection.

4.The difference between a fuse and a circuit breaker is as follows:

1) The principle of the fuse is to use the current to flow through the conductor to heat the conductor, and the conductor melts after reaching the melting point of the conductor, so the circuit is disconnected to protect the electrical appliances and circuits from being burned out. It is an accumulation of heat, so overload protection can also be achieved. Once the melt burns out, the melt is replaced.

2) The circuit breaker can also realize the short circuit and overload protection of the line, but the principle is different, it is through the current bottom magnetic effect to achieve the circuit break protection, through the current thermal effect to achieve overload protection (not fuse, do not need to replace the device).

DC circuit breaker (hereinafter all take TX7-63Z as an example) is used for DC system operation mode conversion or fault removal, with first-class current limiting performance, arc extinguishing advantages, can quickly break the fault current of DC distribution system, can accurately protect relay protection, automatic devices from overload, short circuit and other fault hazards. Here, we will focus on the selection of DC circuit breakers.

We say that the first condition for choosing a product is to understand the product, let's take a look at the classification of DC circuit breaker TX7-63Z:

According to the number of main contact stages, it can be divided into: single-stage, bipolar,

According to the instantaneous tripper, it can be divided into: C type, D type (C type is used for power distribution protection, D type is used for motor protection).

According to the grounding method, it can be divided into: A, B, C type.

Simple, reliable, small size, low price, short breaking time, wide range of current options.

All kinds of products have their own advantages, it is best to use the fuse and circuit breaker together, can not be completely sure that the product of the full range of complete protection to avoid the failure together, the fuse for the large current short circuit protection is more item, its breaking capacity is high and the cost is low, the circuit breaker for the small current overload protection is more item.

First of all, the first advantage, the fuse is relatively cheap. This is also almost the only pressure worth talking about in the fuse.

The circuit breaker is much more powerful, first of all, there are many types of protection. The fuse can only be used for overload protection and short-circuit protection, and leakage protection cannot be realized.

Nowadays, fuses are rarely used, and they are generally from a cost perspective.

In terms of function, it is the same, it is used to cut off the circuit, but the working principle is different.

The fuse works according to the thermal effect of the current, when the current exceeds the fixed value (different fuse fixed value), the fuse in the fuse heats up, the fuse is blown to achieve the segmented circuit, and the protection equipment is not burned out by the high current, and the fuse in the fuse must be replaced every time it is blown again.

Due to the different types of circuit breakers, the principle is also different, but generally due to excessive current, resulting in the tripping coil excitation, it is the circuit breaker tripping. Of course, it is also possible to manually control the opening and closing of the shorts.

The fuse has a fuse, and if there is a fault, it will be blown to protect the equipment.

The circuit breaker is used to control electrical appliances, and when a fault occurs, the circuit breaker will break the circuit, close it and continue to be used.

The fuse is a protective element, which is normally on, and when there is a fault, it will blow, and then the melt core must be replaced. It is not convenient to operate, but it is relatively cheap.

A circuit breaker is a control element that can control the switching on and off of electricity. Easy to operate. Higher than fuses.

In general, circuit breakers can replace fuses.

1. The main advantages and characteristics of the fuse.

Good selectivity. As long as the rated current of the fuse of the upper and lower fuses meets the requirements of the overcurrent selection ratio specified in the national standard and IEC standards: 1, that is, the rated current of the upper fuse is not less than the times of the value of the lower level, it is deemed that the upper and lower levels can selectively cut off the fault current;

Good current limiting characteristics and high breaking capacity;

Relatively small size;

Less expensive.

2. The main disadvantages and weaknesses of the fuse.

The fuse must be replaced after the fault fuse;

The protection function is single, only a period of overcurrent inverse time characteristics, overload, short circuit and ground fault are used for this protection;

When a phase fuse occurs, the three-phase motor will lead to the adverse consequences of two-phase operation, of course, it can be compensated by a fuse with an alarm signal, and the one-phase fuse can disconnect the three-phase;

Remote control cannot be realized, and it needs to be combined with electric knife switches and switches.

3. Non-selective circuit breaker: main advantages and features.

After the fault is disconnected, it can be reset by hand without replacing the components, unless it needs to be repaired after cutting off the large short-circuit current;

The long-delay tripper and the instantaneous current tripper with anti-time limit characteristics have two protection functions, which are used for overload and short-circuit protection respectively, and each performs its own duties;

Remote control can be realized when there is an electric operating mechanism.

4. Major shortcomings and weaknesses.

It is difficult to achieve selective cut-off between the upper and lower non-selective circuit breakers, and when the fault current is large, it is easy to cause the upper and lower circuit breakers to be instantaneously disconnected;

Slightly higher relatively;

Some circuit breakers have a small breaking capacity, such as a circuit breaker with a small rated current when installed close to a large-capacity transformer, which will make the breaking capacity insufficient. Now there are products with high breaking capacity that can be satisfied, but the price is higher.

Summary: Because the short-circuit time of the thyristor module is quite short, and the circuit breaker cannot meet its short-circuit requirements, fuse products are widely used in power distribution systems such as soft starters and frequency conversion in buildings. Moreover, now the state also mandates that fuses must be used in the control and protection of elevators, which are the market for fuse products.

Therefore, it is impossible for a circuit breaker to replace a fuse!