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Inverters play an important role in electric and hybrid vehicles. Its main function is to convert the direct current provided by the on-board battery pack into three-phase alternating current, which is used in motor of the car.
In addition, during regenerative braking, the inverter converts alternating current into direct current to charge the battery pack.
1. The analysis pf system voltage architecture
The choice of inverter switch technology is highly dependent on voltage architecture, so it is important to understand what this means and how it will affect the demand for various types of inverters.
- Light vehicles powered by conventional internal combustion engines
Light passenger cars powered by conventional internal combustion engines use a 12 volt 100ah lithium battery or occasionally 24V system to power internal circuitry such as electronic controllers, lights, and infotainment systems. In order to improve efficiency and emission control, 48V architecture systems were developed.
- Mild and full hybrid powertrains
Electric drives are used, in which an electric motor can assist the combustion engine or supply power directly to the axle. Certain auxiliary systems – such as air conditioning, forced sensing and start-stop functions – can be operated with a 48V auxiliary battery pack, which significantly reduces fuel consumption.
With the power generation capacity to support the vehicle's mild hybrid function, 48V systems will become a common configuration in hybrid vehicles in the coming years.
- All electric and full hybrid powertrains
All-electric and all-hybrid powertrains use high-voltage architectures with voltages typically between 300V and 600V, and in some cases even higher. Electric vehicle drive motors typically operate at high voltages to extract enough power to achieve performance and drivability comparable to or better than that of a fuel-powered vehicle. In terms of the power inverter 3000w used, it is expected that there will be a significant difference between the three voltage levels.
In the low-voltage category, silicon (Si) metal-oxide-semiconductor field-effect transistors (MOSFETs) are the most commonly used type of inverter, while insulated-gate bipolar transistor (IGBT) inverters are most commonly used at medium and high voltage levels. But in the high-voltage category, SiC inverters will be the most commonly used inverters.
2. The type of inverter
There are four types of drive inverters used in electric vehicles, depending on semiconductor switching technology. This section looks at how these technologies stack up with each other and how they are being used by the EV industry.
- Si MOSFET
A MOSFET has three terminals, a source, a drain, and a gate terminal. MOSFETs are more efficient in low voltage applications up to 100V and peak power of 20kW. This is due to small conduction losses and low voltage drop, allowing it to operate at high frequencies. However, as the system voltage increases, high on-losses make the Si MOSFET inverter less efficient.
- IGBT
IGBTs essentially combine the physical characteristics of bipolar transistors and MOSFET diode, giving them the higher current carrying capacity and high switching frequency of MOSFETs. IGBT is a three-phase silicon-based switching device, but instead of a source, drain, and gate terminal, IGBT has an emitter, collector, and gate terminal.
3. The needs of market as well as development
Efficient inverters can extend the range and performance of electric vehicles without significantly increasing the weight or cost of the car. While inverter IGBT has good efficiency, it also has drawbacks due to the silicon material on which it is based.
Compared to SI IGBTs, SiC has higher electric field breakdown capability, better thermal conductivity, higher temperature operation, and higher switching frequency, resulting in lower switching and conduction losses.
SiC's better thermal conductivity allows inverters to dissipate heat faster and more efficiently. This allows for the use of smaller and more cost-effective cooling solutions. SiC inverters are still relatively expensive and are preferred by high-end electric vehicles.
4. Regional demand for inverters
At present, IGBT inverter types account for a large part of China's inverter demand. By 2023, the demand for inverters in Europe is 10.2 million units and will grow to 22.4 million units at a CAGR of 7.4%.
Currently, the most popular type of inverter in the European market is the IGBT inverter type, with a market share of 61%, and the MOSFET inverter type with 31%.
IGBT inverter demand is driven by fully hybrid vehicles, accounting for 37% of demand. SiC inverter types are in low demand, accounting for only 8% of total inverter demand in Europe by 2023. IGBT inverter types account for a large proportion of the demand in the Japan and Korea region.
IGBT inverter types account for a large portion of inverter demand in North America. By 2023, the demand for inverters is 6.3 million units and is expected to reach 25 million units by 2034. Due to the high switching efficiency and low losses of SiC inverters, the demand will be high and will be widely adopted.
5. Conclusion
Having an efficient and lightweight inverter can extend the range and enable faster EV charging. It can also reduce the size of the battery pack, which can save the cost of electric vehicles.
The inverter has a component called a power module with a semiconductor switchgear that generates alternating current by turning it on and off to change the direction of the current.
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