Whether individual car owners revive classic old cars out of environmental protection feelings, or logistics enterprises electrify fleets to reduce operating costs, oil-to-electricity projects are penetrating into various fields at an alarming rate.
However, the road of modification is full of challenges, the most critical of which is the choice of motor, which, like the "heart" of the vehicle, directly determines the success or failure of the modification. Behind the three seemingly simple indicators of cost, power and efficiency, there is a complex art of trade-off: the pursuit of extreme performance may bring high costs, and the emphasis on economy may sacrifice power performance. How to find a balance? This requires not only technical knowledge, but also strategic vision.
As the "heart" of the vehicle, the choice of the motor directly determines the success or failure of the modification effect. We will share the balance of motor selection in the process of oil to electricity from the three dimensions of cost, power and efficiency.
Motor type: four mainstream technical routes
At present, there are four basic types of mainstream drive motors in the market: DC motor, AC asynchronous motor, permanent magnet synchronous motor and switched reluctance motor. Each type has its own unique advantages, disadvantages and applicable scenarios.
Permanent Magnet Synchronous Motor (PMSM)
Because of its high efficiency and power density, it has become a popular choice for new energy passenger cars. This kind of motor is made of permanent magnet material, which can generate magnetic field without external excitation current, and its volume is relatively small, so it can achieve good dynamic response. However, its manufacturing cost is high, and there is a risk of demagnetization in extreme cases, which requires special attention in high load scenarios such as construction machinery.
AC asynchronous motor (AC)
Squirrel-cage induction motor, in particular, has become one of the most widely used types of electric vehicles because of its simple structure and high reliability. It has the advantage of lower cost and ease of maintenance, but is generally not as efficient as a permanent magnet synchronous motor.
Switched Reluctance Motor (SRM)
It is known for its simple structure and robustness, no permanent magnet materials and windings, low manufacturing cost, and good performance in high temperature environment. However, its noise and vibration problems are more prominent, and its control is relatively complex, which is more suitable for commercial vehicles and construction machinery scenarios with low noise requirements.
DC motor
It is a driving motor widely used in early electric vehicles, with simple control, wide speed regulation range and large starting torque. However, with the progress of technology, DC motors have been gradually replaced by AC motors because of their low efficiency, large size and high maintenance costs.
Comparison of characteristics of four motor types
| Motor type | Efficiency | Cost | Maintenance difficulty | Typical application scenarios |
|---|---|---|---|---|
| Permanent Magnet Synchronous Motor | High | High | Medium | Passenger cars, high performance vehicles |
| AC asynchronous motor | Medium | Medium | Low | Commercial vehicle, engineering machinery |
| Switched Reluctance Motor | Medium | Low | Low | Mine card, special vehicle |
| DC motor | Low | Low | High | Transformation of old vehicles |
Cost Considerations: It's Not Just the Purchase Price
The cost consideration is far more than purchase price of the motor, which requires a comprehensive evaluation of the initial cost and the whole life cycle cost.
Initial retrofit cost
Including the cost of the motor itself, the driver, the controller, and the associated auxiliary equipment. Depending on the complexity of the modification, the overall cost of the modification may be tens of percentage points higher than that of the traditional fuel system. For large construction machinery such as excavators, the cost of "oil to electricity" may be tens of percentage points higher than original value.
But the real advantage of electrification is the cost of operation. The energy consumption cost of electric vehicles is usually 30% -70% lower than that of fuel vehicles. In the mining scenario, the energy consumption cost per ton kilometer of the electric mining card is only about a quarter of that of the oil truck. This means that for vehicles with high intensity of use, the upfront investment can be recovered in a relatively short time.
Maintenance costs
It is also the dominant field of electric drive. The electric system does not have the oil, water and air filter system of the traditional engine, so the daily maintenance is simpler and faster. According to the practice in the field of construction machinery, the benefits of maintenance cost savings of electric loaders can reach 15% -20% of the total cost after five years.
Power Matching: Not Just a Numbers Game
Power matching is the key technical factor for the success of oil to electricity conversion, but it is by no means a simple comparison of power figures.
In theory, the rated power of the motor of a vehicle of the same tonnage can be less than that of the original engine. This is because the motor is divided into rated power and peak power, which can be compensated by peak power when working under heavy load to meet the short-term high-load power demand.
The efficiency of the motor can reach 95%, while the thermal efficiency of the diesel engine is generally not more than 45%, which means that the motor is smaller in volume but more efficient in output.
In the actual matching, the application scenario of the vehicle needs to be considered. Urban commuter vehicles may pay more attention to low-speed torque and acceleration performance, while long-distance transport vehicles need to take into account the efficiency performance of high-speed cruise. Construction machinery needs to pay special attention to the power demand of hydraulic system to ensure that the motor can provide stable and continuous power output.
The development of motor has evolved from simple motor substitution to highly integrated electric drive system.
At present, it can be divided into four stages of development: pure motor, miniaturized motor + reducer, integration of electronic control and miniaturized motor + reducer, and highly integrated electric drive bridge. Higher levels of integration generally result in higher efficiency and power density, but with a corresponding increase in initial cost.
Efficiency Optimization: From Single Component to Systems Thinking
Efficiency optimization should not only focus on the efficiency curve of the motor itself, but also take a comprehensive consideration from the system perspective.
The efficient working range of the motor is very important. The advanced axial flux motor can reach 90% efficiency in more than 90% working conditions, with high utilization rate of motor efficiency and low energy consumption. However, some ordinary motors may only achieve peak efficiency in a narrow speed range, which greatly reduces their performance in actual road conditions.
Regenerative braking energy recovery is a unique efficiency advantage of electric drives. In heavy downhill scenarios, such as mine transportation, the motor can convert mechanical energy into electric energy and store it back to the battery to realize the function of "full load downhill charging". This feature enables electric vehicles to operate in some application scenarios with little external charging and only energy recovery.
Thermal management systems are equally important for efficiency maintenance. Motors and batteries will generate heat in the working process, which requires efficient heat dissipation measures. In the process of changing oil to electricity, it is often necessary to design an additional cooling system to ensure that the motor and battery work in the best temperature range, so as to avoid the performance degradation or life shortening caused by overheating.
Practical Case: Balanced Choice of Different Scenarios
Through several practical cases, we can more intuitively understand the art of balance in motor selection.
Conversion of mine truck oil to electricity:
After 15 mining cards were upgraded from oil to electricity in a mining area, about 930000 litres of fuel were saved annually. In this scenario, AC asynchronous motors or switched reluctance motors are selected for their durability and high torque characteristics. Although the efficiency is not the highest, the reliability under harsh conditions is more critical.
Electrification of construction machinery:
After the electric upgrade of a 5-ton fuel loader, the operating cost saved is more than 280000 yuan a year. This type of equipment is suitable for using permanent magnet synchronous motors to balance efficiency and power density, while using electrification to improve operating accuracy and working environment.
Change from oil to electricity for passenger cars:
For the transformation of classic cars, such as the Porsche 911 oil to electricity project, a high-power permanent magnet synchronous motor is selected, with a combined output of up to 500 horsepower and a 100 km acceleration of less than 4 seconds. This kind of modification pays more attention to performance retention and improvement, but cost is a secondary consideration.
Future trend: integration and specialization coexist
Motor technology is still developing rapidly, and two obvious trends are: high integration and application specialization.
Integration
It is manifested in the "all-in-one" design of the electric drive system. From the initial simple motor, to the two-in-one of motor + reducer, and then to the three-in-one of motor + reducer + electronic control, there are now highly integrated electric drive bridge products. Integration reduces connection components, improves system efficiency, and reduces installation difficulties, but may increase maintenance complexity.
Specialization
It is reflected in customized motor design for different application scenarios. High-speed logistics vehicles need high-efficiency interval motors, construction machinery needs high-torque motors, and special vehicles may need special protection levels. With the market segmentation, motor manufacturers have also introduced more targeted products.
There is no best, only the most suitable
Motor selection is essentially a series of balancing arts. There is a subtle trade-off between cost, power and efficiency. The pursuit of the extreme of one indicator is often at the expense of the decline of other indicators.
Motor selection in EV modification is not a mechanical digital comparison, but a dynamic art that requires comprehensive consideration of technology, economy and scene.
From motor type to cost analysis, from power matching to efficiency optimization, every link shows the wisdom of "balance".
In the future, with the integration of intelligent technology, motor selection may be more precise, but the core principle remains the same: adjust measures to local conditions and tailor clothes.
We encourage readers to combine data and experience in practice, while paying attention to the latest developments in the industry, such as the application of silicon carbide devices in electronic control or the progress of wireless charging technology, which may reshape the boundaries of balance.
Ultimately, successful modification is not only the victory of technology, but also the practice of sustainable concept. I hope every choice you make will lead you to a more efficient and green future.