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In the testing and certification industry, "safety testing" refers to the testing and evaluation of product safety to confirm that the product or system complies with relevant safety standards and regulatory requirements, and to ensure that the product will not cause injury or harm to the user or operator in the course of use. The scope of safety testing usually includes mechanical, electrical, chemical, thermal and other aspects, and the test items may involve various components and performance aspects of the product.
High-voltage test is a required test item required by international safety certification bodies. The product must be tested in percentage before leaving the factory. , is an indicator of quality assurance and electrical safety. The test method is to add an abnormal voltage to the product for testing, and this voltage must last for a period of time. Finally, it is determined that as long as there is no insulation breakdown, that is Can be considered to pass this test.
Insulation resistance applies a DC voltage to two related points, up to 1000 volts, and the unit is usually ohms, which can determine good and bad products.
The ground impedance test is to test the ground point of the product. Apply a constant current power supply to the shell or metal part of the product to test the impedance between the two points. Generally, the product requires a test of 25 amps, and the impedance should not be greater than 0.1 ohm. The CSA requires a 40-amp test, which can detect problems such as the grounding point screw is not locked, the grounding wire diameter is too small, and the grounding line is open circuited.
refers to the current that flows through the metal contactable part of the equipment to the grounded part or the accessible part through the human body when the equipment supplies current.
The purpose of the safety input test is to examine whether the input meets the requirements of the product when the product is working normally, and whether the input circuit can withstand the current required by the product when it is working. It is stipulated in the product standard that the input current of the maximum power consumption cannot be greater than 110% of the nominal value of the product. This nominal value also tells the user the minimum current required for the product to work safely, so that the user should prepare such an electrical environment before using the device.
The warning signs for user safety must be stable and reliable, and cannot be used for a period of time because they become blurred, which leads to wrong use by users, which leads to danger, or directly leads to danger. So this stability needs to be tested. In the safety standard, it is stipulated that: test 15S with water, and then test 15S with petroleum spirit, and the logo should not be blurred.
For a device with a pluggable power cord, the power cord is often pulled out of the socket, and the power plug of the socket is pulled out, often being played with or placed arbitrarily. This leads to a problem. The power plug is charged when it is pulled out, and this power disappears with time. If the time is too long, it will cause electric shock to the person playing with the plug, and damage to other equipment if the power plug is placed arbitrarily. or the device itself. Therefore, various safety standards for the whole machine make strict regulations on this time. We design products to consider this time, and the product safety certification needs to measure this time.
SELV circuit is the safe ground voltage circuit. Note: SELV circuits have different interpretations in different standards. For example, the interpretation in IEC60364 is different from IEC60950-1. Therefore, it is necessary to pay attention to which standard SELV is under, and its dangers are also different.
Because the output power of the limited power source circuit is very small, in the known experience, they will not cause the danger of fire, so in the safety standard, the shell of this type of circuit has been specially reduced. Their flame rating is UL94V-2. Therefore, all such circuits need to be measured to prove that they are limited power source circuits.
There is this regulation in the safety standard, and this regulation is the current limiting source circuit. Current-limiting source current requires that under normal circuit and single fault, the outgoing current is below the safety limit, and it will not cause danger to people and be less than 0.25mA. Resistors for isolating primary and secondary circuits are shock-resistant resistors that are required to meet specific standards.
As a support for insulating materials or plastic parts with dangerous voltage, it is necessary to do a ball pressure test to ensure that the plastic parts have sufficient supporting strength when the dangerous voltage parts work at high temperatures. The test temperature is the maximum temperature plus 15°C, but not less than 125°C. Ball pressure time is maintained at the required temperature for 1H.
The humidity test is to simulate the safety performance of the equipment under extreme ring tightness. After the equipment is manufactured, it can operate safely in any humidity, and users cannot be told that the equipment cannot be used because it is the rainy season and the humidity is high. Therefore, it must be considered in the design that the equipment meets the safety requirements under the foreseeable humidity, so humidity testing is a must. There are small differences in test requirements according to different standards.
Torsion test is that the external wire of the equipment is often bent and deformed by external force during use. This test is the number of bends that the test lead can withstand. It will not break due to external force during the product life cycle, and the AC220V wire will be exposed and other dangers.
In the normal use of the equipment, there are often different external forces, such as: relatively tall equipment people will lean on it, or someone will climb it during maintenance; relatively short equipment, the shape is like a stool, some people may stand Wait on it. Because the equipment is subjected to these external forces, the equipment is not designed with careful consideration, which will lead to the danger of equipment collapse and overturning. Therefore, these tests need to be done after the device design is completed. Check that they meet safety requirements.
During the use of the equipment, it will be subjected to various external forces. These external forces may deform the equipment shell. These deformations may lead to dangers inside the equipment, or the indicators cannot meet the requirements. Therefore, these effects must be considered when designing equipment, and these indicators must be tested for safety certification.
Small or tabletop equipment may fall to the ground from the hand or table during normal use. These drops may cause the internal safety indicators of the device to fail to meet the requirements. Therefore, this effect must be considered when designing equipment, and these indicators need to be tested during safety certification. The requirement is that after the device falls, the function can be lost, but it cannot cause danger to the user.
If there is a dangerous circuit inside the device, and the device is in normal use, if the shell is deformed, resulting in dangerous exposure, this is not allowed. Therefore, these effects must be considered when designing equipment, and these indicators must be tested for safety certification.
If there is a rechargeable battery inside the device, a charge-discharge test, a single-fault charging test and an overcharge test are required. This is because the equipment is in normal use, charging and discharging, and the equipment is faulty, but the main function has not been lost, and the user will not find the equipment fault. In this case, the charging and discharging requirements are safe and cannot be caused by this. Danger of explosion, etc.
In the safety test (the temperature of the internal and external surfaces under normal operation), the temperature rise test is the most important. Although the test equipment and instruments are the same as the artificial climate test, the test items, test devices and purposes are very different. The artificial climate environment mainly examines the adaptability and reliability of the equipment. The safety regulations examine whether the equipment can work safely. Here is an example to illustrate their differences: the safety test mainly tests the temperature of the safety device, such as the working temperature of the insulating material under normal conditions, which is lower than the maximum allowable temperature of the insulating material at the highest allowable working temperature of the equipment.
For example, the temperature of the insulating material is 100 ℃ in the 25 ℃ environment, and the insulating material can only operate safely below 130 ℃, which is the key to define the maximum operating temperature allowed by the equipment. If the equipment is at an ambient temperature of 50 ℃, then the insulating material The ambient temperature test temperature converted to 50°C should be 125°C, which meets the requirement of less than 130°C and the test passes. If the ambient temperature of the device is 60°C, the test temperature of the ambient temperature converted to 60°C should be 135°C. If it exceeds the requirement of 130°C, the test fails. Similarly, other safety devices also need to be tested for operating temperature. to determine whether the requirements are met.
After the AC220V circuit passes through a certain resistance, there is no danger to people. So what is the resistance, and what are the requirements for the resistance. Maybe everyone doesn't know. There is this regulation in the safety standard, and this regulation is the current limiting source circuit. Current-limiting source current requires that under normal circuit and single fault, the outgoing current is below the safety limit, and it will not cause danger to people and be less than 0.25mA. Resistors for isolating primary and secondary circuits are shock-resistant resistors that are required to meet specific standards.
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