Safety certification insulation resistance test basis standards and specification requirements

Date：2022-07-14 18:25:58Views：2001

Insulation resistance is the most basic insulation index of electrical equipment and electrical circuits. The detection standard of insulation resistance in the electrical code is that the insulation resistance per kilovolt voltage is not less than 1 megaohm. Common safety test items are introduced as follows:

1. Input test

The purpose of safety regulation input test is to consider whether the input meets the current required by the product during normal operation and whether the input circuit can bear the current required by the product during operation. It is stipulated in the product standard that the input current with maximum power consumption shall not be greater than 110% of the nominal value of the product. This nominal value also tells the user the minimum current required for the safe operation of the product, so that the user should prepare such an electrical environment before using the equipment.

2. Stability test of safety signs

The safety warning signs for users must be stable and reliable, and they cannot be mistakenly used by users or directly lead to danger because they become blurred after a period of use. So we need to test the stability. It is stipulated in the safety standard that 15s shall be tested with water, and then 15s shall be tested with gasoline, and the identification shall not be ambiguous.

3. Capacitor discharge test

For a device with pluggable power cord, its power cord will often be unplugged from the socket. Unplugging the power plug of the socket is often played by people or placed arbitrarily. This leads to a problem. The unplugged power plug is charged, and the electricity disappears with time. If this time is too long, it will cause electric shock to the people playing with the plug, and the arbitrarily placed power plug will damage other equipment or the equipment itself. Therefore, each complete machine safety standard has strict regulations on this time. We need to consider this time when designing products, and we need to measure this time for product safety certification

4. Circuit stability test

1) SELV circuit SELV circuit is a safe voltage circuit. This circuit is safe for users. For example, from the DC output end of the mobile phone charger to the mobile phone, they are safe and can be touched at will without danger.

Note: SELV circuit has different interpretations in different standards. For example, the interpretation in iec60364 is different from that in iec60950-1. Therefore, the risks of SELV are also different under which standard. SELV circuit needs to meet special requirements before it can be a SELV circuit. These requirements still meet the requirements of SELV circuit in case of a single fault. Therefore, each SELV circuit needs to be tested under a single fault to prove that the SELV circuit is stable. During the test, a single fault is introduced one by one to monitor the SELV circuit.

2) Power limiting source circuit

Because the output power of power limiting source circuit is very small, in the known experience, they will not cause fire hazard. Therefore, in the safety standard, the shell of this kind of circuit is specially reduced, and their flame retardant grade is UL94V-2. Therefore, such circuits need to be measured to prove that they are power limiting source circuits.

3) Those who have been engaged in electrician of current limiting circuit know that AC220V circuit is not dangerous to people after a certain resistance. So what is the resistance and what are the requirements for resistance. Maybe you don't know. There is this regulation in the safety standard, which is the current limiting source circuit. Current limiting source current requires that under normal circuit and single fault, the outflow current is below the safety limit, which will not cause danger to people less than 0.25ma. For the resistance of isolating primary and secondary circuits, it is required to meet the impact resistance of special standards.

5. Continuous grounding test

People who have been engaged in electrical installation know that some equipment must be grounded, otherwise there will be dangerous voltage on its touchable surface. These dangerous voltages must be released through grounding. The safety regulation test specifies how much current needs to be used, how long it takes, and the measured resistance must be less than 0.1 ohm, or the voltage drop must be less than 2.5V (use this value if possible)

6. Humidity test

Humidity test is to simulate the safety performance of the equipment under extreme tightness. After the equipment is manufactured, it can operate safely under any humidity. You can't tell the user that the equipment can't be used because it's rainy season and the humidity is high. Therefore, in the design, it must be considered that the equipment meets the safety requirements under the foreseeable humidity, so the humidity test is necessary. The test requirements vary slightly according to the standards.

7. Torque test

Torsion test refers to the bending and deformation of the external wires of the equipment under the action of external forces. This test is to test the bending times that the wire can withstand, and it will not break due to external force during the product life cycle, and AC220V wire will be exposed.

8. Stability test

In normal use, the equipment often has different external forces, such as: people will lean on it when it is relatively high, or someone will climb it during maintenance; The relatively short equipment looks like a stool, and someone may stand on it and wait. Due to these external forces acting on the equipment, the danger of equipment collapse and overturning caused by the Zhou plenary session was not considered in the design of the equipment. Therefore, these tests are required after the equipment design is completed. Check that they meet safety requirements.

9. Shell stress test

During the use of the equipment, it will be affected by various external forces, which may deform the equipment shell, which may lead to internal hazards of the equipment, or the indicators cannot meet the requirements. Therefore, these effects must be considered when designing equipment, and these indicators must be tested during safety certification.

10. Drop test

Small equipment or desktop equipment may fall to the ground from hands or workbench during normal use. These drops may cause the internal safety indicators of the equipment 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 equipment falls, the function can be lost, but it cannot cause danger to the users.

11. Stress release test

If there are dangerous circuits inside the equipment, it is not allowed if the shell of the equipment is deformed during normal use, resulting in dangerous exposure. These effects must be considered when designing the equipment, and these indicators must be tested during safety certification.

12. Battery charge and discharge test

If there is a rechargeable battery inside the equipment, charge and discharge test, charge test and overcharge test under single fault are required. This is because the equipment is in normal use, charging and discharging, and the equipment has faults, but the main functions have not been lost, and the user will not find the equipment fault. In this case, the impulse and discharge requirements are safe, so explosion and other hazards cannot occur

13. Equipment temperature rise test (temperature of internal and external surfaces under normal operation)

In the safety test, the temperature rise test is the most important. Although the test uses the same equipment and instruments as the artificial climate environment test, the test investigation items and test devices and purposes are very different. The adaptability and reliability of the equipment are mainly investigated in the artificial climate environment. The safety regulations examine whether the equipment can work safely.

14. Ball pressure test

As insulating materials or plastic parts supporting hazardous voltage, ball pressure test is required to ensure that the plastic parts have sufficient support strength when the hazardous voltage parts work at high temperature. The test temperature is the maximum temperature plus 15 ℃, but not less than 125 ℃. The ball pressing time is 1H at the required temperature.

15. Contact current test

Contact current is often referred to as leakage current. This current is strictly controlled, and all safety standards have strict regulations. Therefore, this current should be strictly controlled in design and tested during product certification.

16. Voltage withstand test

Voltage withstand test is also called voltage withstand test or high voltage test. It is mainly used to investigate the resistance of equipment insulation and whether the designed insulation meets the design requirements. Different insulation has different test voltage. The withstand voltage test is carried out after the humidity treatment, so as to investigate the resistance of the equipment when it is wet.

17. Abnormal test

Abnormal test is divided into single fault test, error use test, and common abnormal use test. Single fault test refers to that the equipment is required to be safe under a fault state. Incorrect use means that the equipment has a regulating device, or other devices, and is tested in the wrong position or state. It is required that the equipment is safe, which allows the loss of equipment function. Common abnormal use test: refers to some decorative parts that may be added to the equipment because people like beauty, and these decorations are extremely detrimental to the heat dissipation of the equipment. For example, cover a dust cover on the TV and forget to take it off when using the TV. The mobile phone is packed in a mobile phone bag.

18. Safety design

Safety regulation design is a design to meet the safety requirements of products in equipment products. The specific requirements of each standard are different, but the purpose is to protect the safety of users.