Insulation resistance is the most basic insulation index for electrical equipment and circuits. The testing standard of insulation resistance in the electrical code is not less than 1 megohm per kilovolt of voltage. Common safety test items are described as follows:
GM Series Insulation Resistance Testers
1. Input Test
The purpose of the 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 withstand the current required by the product during operation. The product standard states that the input current for maximum power consumption must not be greater than 110 percent of the product's nominal value. The nominal value also tells the user the minimum current required for safe operation of the product so that the user should prepare for such an electrical environment before using the device.
2. Stability test of safety signs
The user's safety warning signs must be stable and reliable, and must not be misused by the user or become blurred due to the use of a period of time and lead directly to danger. So we need to test the stability. Safety standards require that the sign must not be ambiguous when tested with water for 15s and gasoline for 15s.
3. Capacitor discharge test
For devices with a pluggable power cord, the power cord is usually unplugged from the outlet. Power plugs unplugged from the outlet are often played with or left lying around. This can lead to a problem. The unplugged power plug charges and the power disappears over time. If this time is too long, it can cause electrocution to the person playing with the plug, and a randomly placed power plug can damage other equipment or the equipment itself. Therefore, every whole safety standard has strict rules about this. We need to consider this time when designing our products, and we need to measure this time for product safety certification
4. Circuit Stability Testing
1) SELV CircuitThe SELV circuit is a safe voltage circuit. This circuit is safe for the user. For example, from the DC output of a cell phone charger to a cell phone, they are safe to touch at will without danger.
2) Power limiting source circuits
Because power limiting source circuits have a very low output power, in known experience they do not pose a fire hazard. For this reason, the enclosures for such circuits are specifically reduced in safety standards and have a flame retardant rating of UL94V-2. Therefore, measurements of such circuits are required to prove that they are power limiting source circuits.
3) Anyone who has worked as an electrician on current limiting circuits knows that AC220V circuits are not dangerous to people after a certain resistance. So what is resistance and what are the requirements for resistance. Maybe you do not know. There is this provision in the safety standard, which is a current-limiting source circuit. Current limiting source current requirements in normal circuits and single fault out current below the safety limit, will not cause less than 0.25mA danger to people. For the primary and secondary circuits of the isolation resistor, the requirements to meet the special standards of shock resistance.
5. Continuous Grounding Test
Anyone involved in electrical installations knows that some equipment must be grounded or dangerous voltages will be present on its touchable surfaces. These dangerous voltages must be released by grounding. The safety conditioning test specifies how much current needs to be applied, how long it takes, and the measured resistance must be less than 0.1 ohms or the voltage drop must be less than 2.5V (use this value if possible)
6. Humidity Test
The humidity test is designed to simulate the safety of the equipment when it is subjected to extreme sealing. The equipment is manufactured to operate safely at any humidity level. You can't tell the user that the equipment can't be used because it's the rainy season and the humidity is high. Therefore, it is important to design the equipment to meet safety requirements at predictable humidity levels, hence the need for humidity testing. The testing requirements vary slightly depending on the standard.
7. Torsion test
The torsion test refers to the bending deformation of the outer wire of the device under external force. The test is to test the number of bends the wire can withstand and not break due to external force during the product life cycle and the AC220V wire will be exposed.
8. Stability test
In normal use, the equipment often have different external forces, such as: people will lean on it when it is relatively high, or someone in maintenance will climb up; relatively short equipment looks like a stool, someone may stand on it and wait. Because of these external forces on the equipment, the equipment design is not well thought out in the equipment collapse and overturning hazards caused by the equipment. Therefore, these tests are carried out after the design of the equipment has been completed. They are checked for compliance with safety requirements.
9. Shell stress test
Equipment in the process of use, will be subject to a variety of external forces, may make the equipment shell deformation, may lead to equipment internal danger, or indicators do not meet the requirements. Therefore, these effects must be taken into account when designing the device, and the indicators must be tested during safety certification.
10. Drop testing
During normal use, small or desktop devices may fall from hands or workbenches to the floor. These drops may cause the internal safety indicators of the device to be non-compliant. Therefore, this effect must be considered when designing the device and these metrics need to be tested during safety certification. The requirement is that when the device is dropped, functionality can be lost, but it must not pose a danger to the user.
11. Stress Relief Tests
If the device has hazardous circuits within it, it is not permitted to be used if the device enclosure is deformed during normal use, resulting in hazardous exposure. These effects must be taken into account when designing the device and these indicators must be tested during safety certification.
12. Battery Charge and Discharge Tests
If the device has an internal rechargeable battery, it needs to be charged and discharged, charged and overcharged under a single fault. This is because the device is in normal use, charging and discharging state, the device malfunction, but the main function is not lost, the user will not find the device failure. In this case, the pulse and discharge requirements are safe, so there will be no explosion and other hazards
13, equipment temperature rise test (internal and external surface temperatures under normal operation)
In the safety test, temperature rise test is the most important. Although the test uses the same equipment and instruments and artificial climate environment test, but the test investigation project and test device and purpose is very different. The adaptability and reliability of the equipment is mainly investigated in an artificial climate environment. Safety regulations check whether the equipment can work safely.
14. Ball Pressure Test
Plastic parts used as insulation or to support hazardous voltages need to be ball-pressure tested to ensure that the plastic parts have sufficient support strength when working at high temperatures. The test temperature is a maximum temperature plus 15°C but not less than 125°C. The balling time at the required temperature is 1H.
15. Contact current test
The contact current is often referred to as the leakage current. This current is tightly controlled and is strictly regulated by all safety standards. Therefore, this current should be strictly controlled in the design and tested during product certification.
16. Voltage withstand test
Voltage withstand test is also known as voltage withstand test or high voltage test. Mainly used to examine the resistance of the equipment insulation and the design of the insulation to meet the design requirements. Different insulation has different test voltages. The withstand voltage test is carried out after humidity treatment to investigate the resistance of the equipment when wet.
17. Abnormal Tests
Abnormal tests are categorized into single failure tests, misuse tests, and common abnormal use tests. Single fault test means that the equipment is required to be safe in a faulty condition. Incorrect use means that the equipment has a regulator or other device and is tested in the wrong position or condition. Requires the device to be safe, which allows for loss of device function. Common Abnormal Use Tests: are decorative parts that may be added to a device because people like aesthetics, and which are extremely detrimental to the heat dissipation of the device. For example, covering the dust cover on a TV and forgetting to remove it when using the TV. Cell phones in a cell phone bag.
18. Safety design
Safety protocol design is the design of equipment products to meet product safety requirements. The specific requirements vary for each standard, but the goal is to protect the safety of the user.