CN103163421B - A kind of method measuring surge current impact resistant property - Google Patents

Abstract

The invention is used for testing the current impact capability and fusing characteristics of the fuse, and is specifically a method for measuring the anti-surge current impact capability. The technical solution of the present invention is: a device for testing the anti-surge current impact capability of a fuse, which includes a fuse to be tested, a monitoring part, a current limiting resistor, an electronic load, and a power supply, and is characterized in that the monitoring part includes a monitoring oscilloscope and a sampling resistor, the sampling resistor is connected in series with the measured fuse, current limiting resistor, electronic load, and power supply in sequence to form a closed loop, the monitoring oscilloscope is connected in parallel at both ends of the sampling resistor, the power supply is a battery pack connected in parallel, and the electronic load uses To generate periodic surge pulses, when the corresponding current pulses are generated at the sampling resistor, the resistance change and fusing time of the tested fuse are monitored by the monitoring oscilloscope.

Description

A method of measuring the ability to resist surge current impact

technical field

The invention is used for testing the current impact capability and fusing characteristics of the fuse, and is specifically a method for measuring the anti-surge current impact capability.

Background technique

In inductive and capacitive circuits, when the circuit is turned on, there will be an instantaneous surge current, and the fuse of the fuse will have a mechanical impact effect of thermal expansion and contraction when it is impacted by the surge. The first surge impact will cause cracks in the cross section of the fuse, or even directly break the fuse, making the fuse invalid. The invention provides a surge pulse generating device, which can simulate the surge current impact that a fuse may receive when it is used, test the fusing reliability of the fuse, quantify the fusing characteristic parameters of the fuse, and enable the fuse user to further grasp the characteristics of the fuse .

In order to grasp the potential quality and reliability problems of high-reliability fuses used in aerospace, according to ECCC GenericSpecification No.4008, MIL-PRF-23419G and GJB5850 and other related test methods, the limit evaluation of fuse performance is carried out, using conventional tightened test conditions or imposing The step-by-step stress test method is used to investigate the thermal stress, electrical stress and other limit conditions of high-reliability fuses, and to find out their limit capabilities. To provide a reference for the harsh application environment of aerospace.

In the limit evaluation test, anti-surge current impact is an indispensable object of investigation, because a short-term surge current is often generated in the application circuit of the fuse, and the surge current is much larger due to the rapid charging of the input filter capacitor. In the steady state input current, so that the fuse produces mechanical fatigue, reduces the life of the fuse, and even in some cases, it can break the fuse. The surge current is often multiple and continuous pulses, which will cause the fuse to generate heat and change its fuse resistance. Therefore, for aerospace applications, it is very important to measure whether the fuse can withstand a certain amount of current impact.

In the limit evaluation test, the ampere-second characteristic of the fuse (the action of the fuse is realized by the fusing of the fuse, when the current is large, the time required for the fuse to fuse is short. When the current is small, the fuse The time required for fusing is longer, or even not fusing. Therefore, for the fuse, its operating current and operating time characteristics (that is, the ampere-second characteristic of the fuse, which is an inverse time-limit characteristic) are also characteristics that require special attention. Because the fusing characteristics of the fuse mainly consider the protection function, it is hoped that it can cut off the current reliably in time when the circuit fails and overcurrent occurs. This requires the fusing speed of the fuse to be faster; while the melting heat value mainly considers the carrying function, and it is hoped that the fuse can withstand the non-fault pulse current at the moment of the circuit switch, which requires the response speed of the fuse to be appropriately slow; therefore, it is necessary The limit assessment of the fusing time of the fuse is carried out, so as to grasp the fusing time under different current conditions and guide the designer to choose. Therefore, for aerospace fuses, the surge current limit capability test is carried out, and the surge pulse current is used to perform electrical shock on the fuse. By measuring the change rate of fuse resistance, voltage drop and other parameters, evaluate the anti-surge current capability of the fuse.

It is also necessary to test the fuse blowing time under different current conditions for aerospace fuses, so as to obtain the ampere-second curve. Fuses do not need to be tested for pulse current performance in accordance with conventional requirements. However, for aerospace fuses, due to high reliability requirements, it is necessary to test their ability to withstand surge current impacts. Because in inductive and capacitive circuits, the circuit will generate an instantaneous surge current when it is turned on, and the fuse of the fuse will have a mechanical impact effect of thermal expansion and contraction when it is impacted by the surge. In extreme cases, continuous Multiple surge impacts will cause cracks in the cross section of the fuse, or even directly break the fuse, making the fuse invalid.

The surge current waveform of the circuit is diverse, it may be a sine wave, a triangle wave, a sawtooth wave... and its energy can be calculated equivalently. Commonly used test circuits can use circuits such as '555' to build a pulse generating circuit, as shown in Figure 2. Because it is limited by the power supply, the pulse current value will not be too high. If it is too high, overshoot will easily occur. At the same time, the pulse duty cycle setting of the pulse modulation circuit cannot be easily changed.

At present, there are two kinds of fuse fusing characteristic testers commonly used.

One is a test bench built with a constant current source, as shown in Figure 3, the DC power supply in this test circuit is a commercially available constant current power supply, which outputs an overload current, which is recorded synchronously by a timer (usually a frequency meter) The blowing time of the fuse. The practical use of this test device is very limited. The main disadvantages are: (1) There is a switching pulse current in the output. The constant current power supply used by the power supply is to obtain a constant DC current through rectification, filtering, and steady flow of the mains. There must be a switching pulse current with a relatively large peak current. , this switching current can reach several times of the normal output current, although the time is only tens or hundreds of microseconds, it is enough to have an additional impact on the fuse, and even directly break the fuse core. Aerospace fuses are ultra-fast-response fuses, and their fusing time is only a few hundred microseconds at 600% fusing, so it is impossible to truly measure the fusing time of fuses with this test device; The test conditions for appliance fuses are different from those for civilian fuses. The fusing time test of fuses used in spacecraft requires that the open circuit voltage of the test circuit be greater than or equal to the rated voltage of the fuse, generally greater than or equal to 125vdc. At the same time, the maximum specification of the fuse can reach 15A. If the fusing time test of 6I _rating (required by aerospace limit investigation) is to be carried out, the test current must reach 90A. The DC output quality of this high-power power supply is poor and cannot meet the test requirements. Therefore, usually this type of test device can only be suitable for tests that do not require open circuit voltage and test a low fusing point, such as a 250% low overload test.

Another type of tester uses a microprocessor to avoid overload overshoot, but this overload current takes too long to settle. It can be seen from Figure 5 that the establishment time of the overload current reaches 2ms, which is obviously not suitable for the test where the 600% fusing time is only a few hundred milliseconds.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned shortcomings in the prior art, and provide a device for testing the anti-surge current impact capability of a fuse.

In order to achieve the above object, the technical solution of the present invention is: a device for testing the anti-surge current impact capability of a fuse, including a fuse to be tested, a monitoring part, a current limiting resistor, an electronic load, and a power supply, characterized in that: the monitoring part It includes a monitoring oscilloscope and a sampling resistor, the sampling resistor is connected in series with the measured fuse, current limiting resistor, electronic load, and power supply to form a closed loop, the monitoring oscilloscope is connected in parallel at both ends of the sampling resistor, and the power supply is a battery pack connected in parallel, The electronic load is used to generate periodic surge pulses, and when corresponding current pulses are generated at the sampling resistor, the resistance change and fusing time of the tested fuse are monitored by the monitoring oscilloscope.

A method using the above-mentioned device to measure the impact resistance of surge current, is characterized in that it comprises the following steps:

Step 1: Use the four-wire method to measure the internal resistance of the tested fuse;

Step 2: Apply periodic surge pulses to the fuse under test, and the current pulse peak value of the surge pulse is 2-6 times the rated current of the fuse under test;

Step 3: Apply a certain number of surge pulses to the tested fuse, monitor the state of the tested fuse through the monitoring oscilloscope, if the tested fuse does not fail, use the four-wire method to measure the change of the internal resistance of the tested fuse, and Compared with the internal resistance value before the test, the change rate of the fuse resistance value is calculated;

Step 4: Apply a constant current of 2.1, 2.5 and 6 times the rated current of the tested fuse to the unfailed tested fuse, and record the fusing time;

Step 5: According to the change rate of the fuse resistance and the fusing time, judge its ability to resist the impact of surge current, and provide data basis for the selection of the fuse.

Compared with the prior art, the present invention has the beneficial effects as follows:

(1) Product test current loading without overshoot, stable and reliable work, the power supply uses a battery pack, the output DC is pure and the current has no overshoot, especially suitable for fuse testing of aerospace fuses;

(2) The test current can be set arbitrarily, the output current is large, the current in the circuit is adjusted by electronic load, the precision is high, and the output current can be as high as 100A, which meets the requirements of the test current range;

(3) The open-circuit voltage of the circuit can be easily set. Because it is powered by a battery pack, it is only necessary to increase the number of battery packs to achieve the required test voltage. If you want a test voltage of 125Vdc, connect 11 12V battery packs in series. ;

(4) Time measurement is accurate. For millisecond and microsecond fusing time, the most effective measurement method is to use an oscilloscope to record. The oscilloscope not only has fast response and accurate timing, but also can reflect the whole process when the fuse is blown, especially the arcing phenomenon that may occur when the fuse is blown.

Description of drawings

Fig. 1 is a schematic circuit diagram of the present invention;

Fig. 2 builds the schematic diagram of the pulse generating circuit for the 555 circuit in the prior art;

Fig. 3 is the schematic circuit diagram of the test bench built by the cross current source in the prior art;

Fig. 4 is the test output waveform figure that the oscilloscope of the present invention monitors;

Fig. 5 is the overshoot wave form diagram that the microprocessor avoids loading overload in the prior art;

Fig. 6 is the fusing time waveform recorded by the oscilloscope of the present invention.

Among them, in Figure 1-3, 1: monitoring oscilloscope; 2: sampling resistor; 3: circuit protection fuse; 4: battery pack; 5: electronic switch; 6: electronic load; 7: current limiting resistor; Measuring fuse; 9: constant current power supply; 10: 555 oscillator; 11: timer.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Embodiments of the present invention are shown in Fig. 1,4,6 with reference to.

As shown in Figure 1, a device for testing the anti-surge current impact capability of a fuse includes a fuse under test, a monitoring part, a current limiting resistor, an electronic load, and a power supply, and is characterized in that the monitoring part includes a monitoring oscilloscope and a sampling resistor, The sampling resistor is connected in series with the measured fuse, current limiting resistor, electronic load, and power supply in order to form a closed loop. The monitoring oscilloscope is connected in parallel at both ends of the sampling resistor, the power supply is a battery pack connected in parallel, and the electronic load is used to generate For periodic surge pulses, when corresponding current pulses are generated at the sampling resistor, the resistance change and fusing time of the tested fuse are monitored through the monitoring oscilloscope.

Furthermore, it also includes an electronic switch and a circuit protection fuse, the electronic switch is located between the power supply and the electronic load, and the circuit protection fuse is located between the power supply and the sampling resistor.

Further, the current-limiting resistor is a sliding wire rheostat with an adjustable resistance range of 0~1Ω, which is used to adjust the pulse current value in the circuit;

The resistance value of the sampling resistor is 0.1Ω;

The electronic load is an arbitrary waveform generator, which outputs periodically changing square wave pulses to simulate surge pulses, the pulse peak current is 2-6 times the rated current of the tested fuse, the pulse duration is 10ms, and the period is 10s, or Output periodic sine wave pulses, the pulse peak current is 2-6 times of the rated current, and the period is 10s.

When using this device for anti-surge current shock test, select the voltage value of the battery pack and the resistor of the sliding wire rheostat according to the output pulse current to ensure that the required pulse current value can be output. Set electronic load parameters according to specific test requirements, including pulse peak current, pulse width, cycle, and pulse times.

Figure 4 is the test output waveform of the pulse peak value 10A, pulse width 200ms, period 10s, and rise and fall rate 1A/us monitored by the oscilloscope.

Electrical shocks are applied to fuses using inrush pulse currents. By measuring the change rate of fuse resistance value, fusing time and other parameters, evaluate the anti-surge current capability of the fuse.

No matter the fuse used in the AC or DC circuit, the melting time of the fuse is tested by loading the DC overload current to cause the fuse core to be heated and blown. Therefore, whether the DC of the fuse is pure or not is related to the correctness of the melting time. And when a large current is overloaded, the fusing time may be only a few hundred microseconds. If there are too many AC components in the DC, the impact will be very serious.

In this regard, the present invention provides a method of using the above-mentioned device to measure the anti-surge current impact capability, which is characterized in that it includes the following steps:

Step 1: Use the four-wire method to measure the internal resistance of the tested fuse;

Step 2: Apply periodic surge pulses to the fuse under test, and the current pulse peak value of the surge pulse is 2-6 times the rated current of the fuse under test;

Further, the peak value of the current pulse is specifically 3 times the rated current of the tested fuse;

Step 3: Apply a certain number of surge pulses to the tested fuse, monitor the state of the tested fuse through the monitoring oscilloscope, if the tested fuse does not fail, use the four-wire method to measure the change of the internal resistance of the tested fuse, and Compared with the internal resistance value before the test, the change rate of the fuse resistance value is calculated;

Further, the number of times the surge pulse is applied is 10,000 or 20,000 times, the cumulative test period is 100,000 seconds or 200,000 seconds, and the cumulative pulse duration is 100,000 milliseconds or 200,000 milliseconds;

Step 4: Apply a constant current of 2.1, 2.5 and 6 times the rated current of the tested fuse to the unfailed tested fuse, and record the fusing time;

Step 5: According to the change rate of the fuse resistance and the fusing time, judge its ability to resist the impact of surge current, and provide data basis for the selection of the fuse.

Figure 6 shows the fusing time waveform recorded by the oscilloscope.

The specific test conditions and results are as follows:

1. Anti-surge ability test

This device is used to test the anti-surge current capability of a domestic fuse. The test conditions are as follows:

Select 6 fuses of two specifications for the test,

a Use a sine wave pulse current to impact the test sample.

b The test pulse parameters used are as follows:

Pulse waveform: square wave

Pulse peak current: 3 times rated current

Pulse duration: 10ms

Cycle: 10s

The test results are shown in Table 1:

Table 1

Through 20,000 pulse tests, it can be concluded that the anti-surge pulse ability of type 1 fuse is better than that of type 2, which provides a data basis for the selection of aerospace fuses.

2. Fusing time limit test

At room temperature, apply 2.1 times, 2.2 times, 2.3 times...6 times the rated current to the samples of type 1 fuses with sample numbers 1 and 2 that have not been blown after 20,000 pulse impacts in the above test, and pass the device test Fuse blowing time.

The test results are shown in Table 2:

Table 2

By comparing the fusing time of the fuses in 2 under the same current conditions, it is concluded that the fusing time of type 1 is much shorter than that of type 2, and the fusing characteristics are due to type 2. Provide data basis for the selection of aerospace fuses.

The above-mentioned embodiment is only an embodiment of the present invention, but should not be construed as limiting the scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (1)

1. A method for measuring surge current impact resistance, characterized in that the method uses a device for testing the surge current impact resistance of a fuse, including a fuse under test, a monitoring part, a current limiting resistor, and an electronic load , power supply, the monitoring part includes a monitoring oscilloscope and a sampling resistor, the sampling resistor is connected in series with the measured fuse, current-limiting resistor, electronic load, and power supply to form a closed loop, and the monitoring oscilloscope is connected in parallel at both ends of the sampling resistor, and the power supply is A battery pack connected in series, the electronic load is used to generate periodic surge pulses, and when the corresponding current pulses are generated at the sampling resistor, the resistance change and fusing time of the tested fuse are monitored by the monitoring oscilloscope, It also includes an electronic switch and a circuit protection fuse. The electronic switch is located between the power supply and the electronic load. The sliding wire rheostat is used to adjust the pulse current value in the circuit, the resistance value of the sampling resistor is 0.1Ω, the electronic load is an arbitrary waveform generator, and the output square wave pulse simulates a surge pulse, and the pulse peak current is 2-6 times the rated current of the tested fuse, the pulse duration is 10ms, and the period is 10s, or the output sine wave pulse, the pulse peak current is 2-6 times the rated current of the tested fuse, and the period is 10s , including the following steps: Step 1: Use the four-wire method to measure the resistance of the tested fuse; Step 2: Apply periodic surge pulses to the fuse under test, and the peak value of the current pulse of the surge pulse is three times the rated current of the fuse under test; Step 3: Apply a certain number of surge pulses to the tested fuse, monitor the state of the tested fuse through the monitoring oscilloscope, if the tested fuse is not invalid, use the four-wire method to measure the change of the tested fuse resistance, and compare with The resistance value is compared before the test, and the change rate of the fuse resistance is calculated. The number of surge pulses applied is 10,000 or 20,000 times, the cumulative test period is 100,000 seconds or 200,000 seconds, and the cumulative pulse duration is 100,000 milliseconds or 200,000 millisecond; Step 4: Apply a constant current of 2.1, 2.5 and 6 times the rated current of the tested fuse to the unfailed tested fuse, and record the fusing time; Step 5: According to the change rate of the fuse resistance and the fusing time, judge its ability to resist the impact of surge current, and provide data basis for the selection of the fuse.