How much do you know about the use of common pure electric vehicle maintenance and disassembly tools and testing instruments
- Disassembly tools
(1) The concept of insulation
Insulation refers to a safety measure that isolates or wraps a charged body with a non-conductive substance (insulating material) to protect against electric shock.
(2) The necessity of insulation
Good insulation is a necessary condition to ensure the operation of equipment and lines, and it is also an important measure to prevent electric shock accidents, leakage and short circuits. Good insulating materials also have the functions of heat dissipation and cooling, mechanical support and fixation, energy storage, arc extinguishing, moisture proof, mildew proof and conductor protection.
- Insulation disassembly tool
Insulation disassembly tools are tools that use insulating materials for processing and are suitable for operations such as disassembly and assembly of electrical systems, as shown in Figure 1. Insulation and disassembly tools must be used for the disassembly and assembly of high-voltage parts of pure electric vehicles. The insulating disassembly tool must be equipped with an insulating handle with a withstand voltage of more than 1000V.
Second, the detection instrument
The detection instruments used in the maintenance of pure electric vehicles include digital multimeters, insulation resistance testers (such as insulation resistance meters, high-voltage insulation testers), clamp ammeters, high-voltage battery maintenance diagnostic instruments, and fault diagnosis instruments.
- Digital multimeter
The digital multimeter should meet the requirements of CAT III safety level. Figure 2 shows the actual UT505A digital multimeter. Multimeters usually have the functions of detecting AC/DC voltage, current, resistance, frequency (Hz) temperature (TEMP), diode, continuity, capacitance, insulation test (low voltage) and so on. Some car-specific multimeters also have rotational speed (RPM) percentage (duty cycle, %), pulse width (ms) detection, and other functions (such as the use of buzzers for fault code reading).
- Insulation resistance meter
The operation of pure electric vehicles is very complex. During the operation, there will inevitably be collisions, friction and extrusion between components, resulting in a decrease in the insulation performance between the high-voltage circuit and the vehicle chassis. The positive and negative leads of the power supply will form a leakage current loop through the insulating layer and the chassis. When the multi-point insulation performance declines between the high-voltage circuit and the chassis, it will also cause the heat accumulation effect of the leakage circuit, which may cause an electrical fire in the vehicle. Therefore, the real-time detection of the electrical insulation performance of the high-voltage electrical system relative to the vehicle chassis is the core content of the electrical safety technology of pure electric vehicles. When testing the electrical insulation performance, it is necessary to use a special insulation test instrument to measure whether the insulation resistance of high-voltage cables and parts to the body is within the specified value range.
There are many instruments for insulation testing, such as digital multimeter (DMM), insulation resistance meter, insulation test multimeter or withstand voltage tester, etc. The most commonly used test instrument is insulation resistance meter.
There are many types of insulation resistance meters, but their functions are roughly the same. The commonly used insulation resistance meter, commonly known as the shake meter, is a testing instrument used to measure large resistance and insulation resistance.
When selecting an insulation resistance meter, it is stipulated that the voltage level of the insulation resistance meter should be higher than the insulation voltage level of the measured object. When measuring the insulation resistance of equipment or lines with a rated voltage below 500V, a 500V or 1000V insulation resistance meter can be used; when measuring the insulation resistance of equipment or lines with a rated voltage above 500V, a 1000~2500V insulation resistance meter should be used; when measuring insulators 2500~5000V insulation resistance meter should be used. In general, when measuring the insulation resistance of low-voltage electrical equipment, an insulation resistance meter with a range of 0~200MΩ can be used.
As long as the insulation resistance meter is shaken at a constant speed of about 120r/min when the pointer is not zero, the pointer will be stable at a certain position on the dial. According to the displayed value and space on the dial, the insulation resistance of the measured line can be correctly read. .
- Clamp ammeter
Clamp ammeters are also called digital current clamps. In electric vehicle maintenance and diagnosis, it is necessary to measure the current in the wire. Due to the large alternating currents in the wires of the drive system (eg between the inverter and the motor), indirect measurements must be made with a pin ammeter.
A typical clamp-type ammeter is shown in Figure 4, which is a portable electrical test instrument made according to the principle of current mutual inductance. Its working part is mainly composed of an ammeter and a through-core current transformer. The core of the through-core current transformer is made into a movable opening and is clamped, so it is called a clamp ammeter. Clamp ammeter is a portable instrument that can directly measure the AC current of a circuit without disconnecting the circuit.
- High-voltage battery maintenance and diagnostic instrument
After replacing a group of batteries inside the high-voltage battery pack of an electric vehicle, it is necessary to match the performance of the replaced battery pack to ensure that the performance of the new battery pack is consistent with that of the entire battery pack. This requires the use of special battery maintenance and diagnostic tools. Assisted completion. Usually, the power battery maintenance and diagnostic instrument supports the discharge of high-voltage power batteries, battery unit maintenance and other operations, and supports the detection of battery pack data and the upgrade of vehicle software through U8B.
Automotive electronic control system fault diagnosis instrument is used for fault diagnosis of corresponding models, also known as decoder, fault scanner, etc. Different models use different fault diagnosis instruments. For example, BAIC New Energy Vehicle adopts BDS fault diagnosis system (BAIC BJEV Diagnostic System). The diagnosis software is installed on the computer terminal and connected to the vehicle OBD diagnosis socket through a communication cable (diagnosis box). Communicates with the vehicle’s control module for troubleshooting. BYD electric vehicle fault diagnosis instrument model is ED400, which can complete fault code reading, clearing, data flow reading, actuator action test, basic system setting, software upgrade, programming, coding and ABS master cylinder function of the control module. The fault diagnosis instrument used in BMW electric vehicles is BOS.
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