Short-circuit protection and overload protection are of great use in daily life. Whether it is used in household appliances, anti-resistance originals, or mobile terminals, how does short-circuit protection and overload protection protect circuit safety? What is the principle? What? Next, Xiaobian will answer you one by one.
Short-circuit protection is a failure in the circuit. For example, the resistance of the wire is almost negligible without passing through the load. Therefore, the extremely large current generated instantaneously provides a power cut to prevent equipment damage and accidents.
Short-circuit protection means that the power supply can be cut off quickly and reliably after a short-circuit fault occurs in the electrical circuit to prevent the electrical equipment from being damaged by the impact of the short-circuit current. Under normal circumstances, the short-circuit protection device should be installed closer to the power supply terminal, which is usually installed under the power switch. This can not only expand the range of short-circuit protection, but also can isolate the electrical circuit from the power supply, making it easier to install. And repair. For some devices with short-circuit protection requirements, the short-circuit protection device should be installed close to the protected device.
The short circuit protection of the circuit breaker refers to a kind of protection in which the currents such as phase, phase zero and phase ground increase in vain. Leakage protection does not work for non-grounded shorts.
Example to explain how short circuit protection worksThe short circuit protection circuit uses a transistor to sample the output voltage, and determines whether a short circuit occurs according to the state change of the output voltage before and after the short circuit, thereby realizing the short circuit protection short circuit protection circuit and the working principle circuit. The short circuit protection circuit and the working principle are as shown in FIG. Indicate short circuit or not, then we add a light-emitting diode to make the indicator light, as shown in Figure 2, after the short circuit occurs, the light-emitting diode D3 is bright, after the short circuit is eliminated, the power supply is restarted, the circuit can resume normal operation, the short-circuit protection circuit and Working principle is as follows
The working principle is as follows: after the short circuit occurs, the output voltage is sampled by RA and RB, and the voltage value cannot be maintained. The transistor Q1 is turned on, so that Q1 is turned off, the capacitor C1 is charged, and the voltage of the VEN connected to the AP3003 EN pin rises with time. High, the expression is as shown in (E-3). Once the VEN is higher than the threshold voltage of the EN pin, the whole system stops working and the short-circuit protection function is realized.
The short-circuit protection design needs to pay attention to two aspects. First, it is necessary to avoid the short-circuit protection circuit affecting the system startup. The selection of R1 and C1 should ensure that the short-circuit protection starts to operate much longer than the system startup time. The second is to select the appropriate R3 to ensure The addition of R3 does not affect the output voltage values ​​set by RA and RB.
What is overload protection?Overload is the overload, which exceeds the rated load of the equipment itself. The phenomenon is that the current is too large, the electrical equipment is heated, the long-term overload of the line will reduce the insulation level of the line, or even burn out the equipment or line; in general, it exceeds the equipment. The rated load capacity is overload. If the motor is blocked, the crane will not move.
What is overcurrent protection?Overload protection is actually overcurrent protection: as the name suggests, the current is too large, the reasons are many, such as overload of electrical equipment (such as the above), short circuit (including short circuit), equipment insulation damage and so on.
Exceeding the rated current value defined by the circuit design is overcurrent, such as thermal relay action, overcurrent relay protection action, circuit breaker trip, etc.
The difference between overload protection and short circuit protectionBefore we also said the so-called overload protection, that is, overcurrent protection, the so-called overcurrent, that is, the current flowing through electrical equipment and lines, not only exceeds its rated current value, but also exceeds the time it is allowed to withstand.
Overcurrent allows for both overcurrent and fault overcurrent. When the squirrel cage motor starts, its starting current is much larger than the rated current, but it does not exceed the allowable time, so it is allowed to overcurrent.
Overload protection is for fault overcurrent. Short circuit is also an overload and is a serious overload phenomenon. It can cause great damage to electrical equipment and circuits, and even cause fires.
Overload protection generally uses an inverse time overcurrent protection device, that is, the greater the current flowing through the protection device, the shorter the time limit of the action. The fuse also has a certain inverse time characteristic. There are also bimetal thermal relays.
Short-circuit protection generally uses momentary action, that is, 0 second action. There are electromagnetic, electronic and other forms.
power connector is used in power module system. It can select the matching power + signal connector according to the need. The feature is that the number of power and signal contacts and the matching sequence can be selected arbitrarily while keeping the connector size and contact core number unchanged.
Plug (male) / socket (female) can be installed at 90 or 180 degrees. It supports mixed or independent combination of signal and power. The quantity range of power and signal is (2-16) pin and (12-128) pin respectively
Product features
High temperature resistant, glass fiber reinforced and flame retardant polyester is used as insulation material
Copper gold composite conductor with high conductivity is used, and the contact area of the conductor is plated with gold
It adopts shrapnel contact, which has the characteristics of integration, small volume, large current carrying capacity, soft plug-in, blind plug-in, self guidance and high dynamic contact reliability. This series of products can be interchanged with FCI's powerblade series and Tyco's multi-beam series
There are three sizes of center distance of power contact: 5.08mm, 6.35mm and 7.62mm
The length of power hole / signal pin can be selected in two sizes. The power rated current is 45A and the signal rated current is 2.5A
Power+ Signal Power Connector
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