What is the insulation resistance standard for electric vehicles?
2 Answers
Under the maximum working voltage, the insulation resistance Ry1 of the DC circuit should not be less than 100Ω/V, and the AC circuit should not be less than 500Ω/V. This refers to the current flowing through the surface layer of insulating materials in the system. The larger the value, the worse the insulation performance of the system. Hazards of electrical insulation failure: If electrical insulation fails in the system, it can lead to progressive consequences depending on the severity. A single point of insulation failure may not have an immediate noticeable impact on the system; however, multiple points of insulation failure can cause leakage current to flow between these points, accumulating heat in nearby materials, which may lead to a fire under certain conditions. Method of external resistance measurement: A series of resistors is connected between the positive and negative poles. By controlling the switches in the circuit, voltage values across the resistors can be obtained in two states. By setting up circuit state equations and solving them simultaneously, the resistance values from the positive and negative poles of the power battery to the ground can be determined, assessing the insulation condition of the battery poles relative to the ground.
I just checked the information, the national standard for electric vehicle insulation resistance requires no less than 100Ω/V. For example, my 400V electric car has a minimum threshold of 40kΩ. However, this is just the safety baseline. When new cars leave the factory, they usually qualify only when reaching several tens of megaohms. The other day when I took my car for maintenance, the mechanic used a megohmmeter to test it, and it showed 120 megaohms. I always pay special attention to waterlogged sections when driving. After the heavy rain last time, a yellow warning light popped up on the dashboard, so I immediately went to the inspection station to check the insulation value. It turned out that water had seeped into the wiring harness connector at the wheel arch, and timely treatment prevented major trouble.
