Application Analysis of Thin Film Capacitor in New Energy Vehicles
New energy vehicles refer to the use of unconventional vehicle fuel as a source of power. New energy vehicles include hybrid vehicles, pure electric vehicles, fuel cell electric vehicles, hydrogen engine vehicles, and other new energy sources (such as high-efficiency energy storage, dimethyl ether ) Products of various categories such as automobiles.
Motor, battery and motor control technologies are the three cores of new energy vehicles. The core of the motor control technology is the inverter technology that requires efficient motor control. The inverter technology of high efficiency motor control requires a powerful IGBT module and a matching DC support capacitor
Technical advantages of film capacitors:
1. Good product safety and strong overpressure resistance
Since the film capacitor has a self-healing phenomenon, and the design of the film capacitor is in accordance with the standard of 1EC61071, the anti-surge voltage capability of the capacitor is greater than the rated voltage of 1.5, and the capacitor adopts the split film technology, and the capacitor will not theoretically produce short-circuit breakdown. Phenomenon, which greatly improves the safety of such capacitors, the typical failure mode is an open circuit. The ability of the capacitor to withstand peak voltages in specific applications is also an important indicator for investigating capacitors. In fact, for electrolytic capacitors, the maximum surge voltage allowed is 1.2 times, this situation forces the user to have to consider the peak voltage rather than the nominal voltage.
2. Good temperature characteristics, wide range of product temperature, can be from -40℃-105℃
The high-temperature polypropylene film used in DC supporting film capacitors has the temperature stability that polyester films and electrolytic capacitors do not. As the temperature increases, the capacity of polypropylene film capacitors generally decreases, but the rate of decline is very small. It is probably 300PPM/C; and whether the polyester film is in the high temperature stage or the low temperature stage, the capacity changes greatly with the temperature, which is +200~+600PPM/C.
3. Stable frequency characteristics and good high-frequency characteristics
At present, most controllers have a switching frequency of about 10KHZ, which requires good high-frequency performance of the product. For electrolytic capacitors and polyester film capacitors, this requirement is a problem.
4. No polarity, can withstand reverse voltage
The electrode of the film capacitor is a nano-scale metal deposited on the film, and the product has no polarity, so it is very convenient for users, and does not need to consider the problem of positive and negative electrodes; and for electrolytic capacitors, if it exceeds 1.5 When the reverse voltage of times Un is applied to the electrolytic capacitor, it will cause the internal chemical reaction of the capacitor. If this voltage lasts long enough, the capacitor will explode, or the electrolyte will flow out as the internal pressure of the capacitor is released.
5. High rated voltage, no need for series and balancing resistors
In order to increase the output power, the bus voltage of hybrid vehicles and fuel cell vehicles has a tendency to increase continuously. At present, the typical battery voltages provided to the motor on the market are 280V, 330V and 480V, and the matching capacitors are different from different manufacturers, but generally they will choose such as 450V, 600V, 800V, and the capacity from 0.32mF to 2mF, and The rated voltage of the electrolytic capacitor is not higher than 500V, so when the bus voltage is higher than 500V, the system can only increase the withstand voltage level of the capacitor bank by connecting electrolytic capacitors in series. In this way, not only increases the volume and cost of the capacitor bank, but also increases the inductance and ESR in the circuit.
6. Low ESR, strong resistance to ripple current
The film capacitor is greater than 200mAμF, and the electrolytic capacitor’s ability to pass ripple current is 20mAμF. This feature can greatly reduce the capacity of the capacitor required in the system. Domestic manufacturers such as Xiamen] The products currently promoted by Farah are currently 04-0.5m2, and the maximum ripple current value ranges from tens of amps to hundreds of amps.
7. Low ESL
The low inductance design of the inverter requires its main component DC-Link capacitor to have extremely low inductance. The high-performance DC-Link DC filter film capacitor integrates the bus into the capacitor module to minimize its self-inductance (<30nH), which greatly reduces the oscillation effect at the necessary switching frequency. Therefore, the absorption capacitance connected in parallel to the DC-Link capacitor_ is often omitted, and the capacitor electrode is directly connected to GBT.
8. Strong anti-surge current capability
Can withstand instantaneous large current. Using wave cutting technology and capacitor coating thickening edge technology can improve the product’s ability to surge current temperature and mechanical shock
9. Long life
The thin film is not easy to aging, which determines the excellent long life of the film capacitor. Especially at rated voltage and rated temperature, the service life is more than 15000 hours; if the average is 30Km/H, the life span of the capacitor can be 450,000Km. The mileage of the car is sufficient.
