Since the beginning of this century, the Chinese government has vigorously advocated environmental protection, and through government funding to help domestic enterprises to develop electric vehicles. Through efforts, in recent years, the domestic electric vehicle technology has gradually matured. A number of well-known domestic brands such as Shanghai Roewe, BYD, Changan Automobile, Jianghai Automobile, Geely Automobile and Guangzhou Automobile Chuanqi have emerged, and they have begun to occupy a part of the automobile market.

The bottleneck in the current development of electric vehicles is how to achieve fast charging. At present, the mainstream charging modes are slow charging and fast charging. Slow charging is generally used for home use, during the day, charging at night, charging time is relatively abundant, generally 7 to 12 hours, using the mains, charging it through the car charger, the power is relatively small. The fast charge uses the DC charging pile outside the vehicle, and it is charged with a large current. The maximum current can reach 135A, which can be filled in one hour.

In the past two years, DC charging pile technology has developed rapidly. The DC charging pile enterprises have sprung up, and their competition is also very cruel. Who can solve the problem of battery heating during charging, effectively protect the battery of electric vehicles, who can increase the charging power and shorten the charging time, who will grab a bigger market.

It is well known that battery heating is mainly caused by heat generated by chemical reactions and generated by ripple current. For the charging pile power module, to reduce the heat of the battery, it is necessary to reduce the output current ripple of the output power module. At present, the industry generally adopts a range of ≤±0.5%. According to this standard, if the high-power fast charging mode is used, the absolute ripple current value is still quite large. In fact, the heat of the battery is still relatively high, so to do fast charging, it must be much smaller than this standard. At present, manufacturers with strength are controlled within the range of ≤±0.15%, and a few manufacturers can control within ≤±0.1%.

Why does the output produce ripple? First of all, when the grid is input, due to various loads, it is not a regular sine wave, which is mixed with a large number of harmonics of various frequencies in various bands. Secondly, in the circuit, various harmonics are generated due to the operation of various power components.

So how do you reduce the output ripple? Circuit design, line layout, component options, etc. can reduce the output ripple. Capacitors play a crucial role in circuit filtering.

According to the above power module, the input terminal is rectified by PFC, and the alternating current is converted into a direct current, and then the high-frequency rectification is performed to output a required direct current. The electrolytic capacitors of the PFC rear stage adsorb a large number of low- and medium-frequency harmonics while flattening. Provides a stable input DC current for the rear DC-DC section. The ripple of the DC current input at this location is reduced, which plays a key role in reducing the output ripple from the source to the output. The electrolytic capacitor behind the output further filters the ripple in the output current after high-frequency rectification to ensure that the ripple of the current at the output is reduced to a minimum. At the same time, it prevents the violent fluctuation of voltage and protects the battery.

The charging pile is generally used outdoors, and the conditions are relatively complicated. If the charging pile is to be operated for a long time, the core is to ensure the normal and smooth operation of the charging power module. This requires capacitors with long-term high stability and can adapt to a variety of outdoor weather.

The special capacitors for charging piles mainly need to solve the above problems from the following aspects:

1. The capacity of the capacitor is less attenuated in the harsh requirements. The larger the capacity of the capacitor, the stronger the ripple resistance is, the stronger the ability to absorb ripple, and the less the circuit ripple damages the capacitor, ensuring the longer the life of the capacitor. This ensures that the output ripple of the charging pile DC power supply is reduced and that it is stable for a long time.

2. The high temperature characteristics of the capacitor are good. When the capacitor is in operation, the temperature is generally between 50 ° C and 70 ° C. When there is a problem with the high-temperature characteristics of the capacitor, during operation, as the temperature increases, the leakage current increases more. As the leakage current increases, the internal temperature will increase due to this current, which causes a vicious cycle, which leads to a shortened product life. At the same time, the ability of the capacitor to absorb ripple is also rapidly reduced, so that the output ripple of the DC charging power supply of the DC charging pile cannot be reduced, and it is certainly not stable for a long time.

3, the low temperature characteristics of the capacitor is better. In some northern regions, the nighttime temperature is relatively low, and the charging pile does not work, its internal temperature is relatively low, it may be at -25 °C. As we all know, the lower the temperature, the greater the change in capacity. When the product is -20 °C, the capacitance holding rate is about 75%. At -30 °C, the capacitance holding rate is about 50%, and to -40. At °C, its capacity holding rate is only about 12%, and some of the nearly the same capacitance can not be measured. When the charging pile is not used for a long time, its internal temperature is as low as -30 °C. If the charging pile is started, the capacity of the capacitor is limited, and its ability to absorb ripple is limited, and a large amount of ripple will enter the rear DC. The -DC part, which impacts other chips and components, causes some components to fail, and the probability of a capacitor exploding also rises linearly. Of course, protection is now set in the charging pile module, but protection means that the charging pile cannot be used normally. If the charging pile that we put into use often has this problem, then this charging pile will not be recognized by consumers, and the country will not allow it to be put into use.

Yaskawa SGM7A Type Servo Motor

Yaskawa Low inertia, high speed servo motor SGM7A

Yaskawa SGM7A type servo motor

Wuxi Trenty Machinery & Equipment Co., Ltd. , https://www.elec-inverter.com