Topic:
Is the electric motor reliable for off-roading?
In the field of off-road vehicles, there is a new class of vehicles that stand out, such as plug-in hybrids, range extender or pure electric off-road vehicles driven by pure electric motors, which have super low torque and explosive power, and at the same time have very low energy consumption; Or because of the low unit price of electricity, the fuel consumption of using the internal combustion engine to power the electric motor is also low, so this type of car is becoming the first choice for ordinary off-road vehicle enthusiasts.
However, traditional off-road vehicle manufacturers and enthusiasts generally do not recognize these cars, because they think that off-road with electric motors is a dangerous thing, so whether the motor is suitable for off-road, and whether there are potential safety hazards for off-road? Let's talk about this topic.
Overload and spontaneous combustion
First of all, the answer is clear:
Heavy off-road with electric motors is dangerous, but fuel vehicles are no exception.
Whether it is a drive motor for a car or an electric motor for electrical appliances within reach, as long as it runs for a long time, it will heat up, such as the electric fan that the author is using; If you touch the shell of the motor from the top to the night, the temperature will be significantly higher than the room temperature, and there are four main reasons for the increase in temperature.
Specifically:
- Large loads
- High voltage
- High temperatures
- failure
If the motor is in a high load state for a long time, it will produce too much heat energy, the motor has two parameters: rated power and maximum power, the rated power can be understood as the power that can be stably output when the motor continues to run, or the power that the motor can continue to operate under standard heat dissipation conditions without power drop. The operation of the motor at the rated power can ensure the reasonable heat generation and the stability of the service life, and the key point is that there will be no failure in general.
"Maximum power" refers to the maximum power that the motor can output in a short period of time, and the standard often far exceeds the rated power, so the maximum power can only be maintained for a few seconds or at most a few minutes under the premise of unchanged heat dissipation conditions - 30 seconds is the rule. Of course, the specific standards for automotive motors will be different, but the real standards cannot be verified, after all, no car company will release the verification results after loading.
Now what needs to be figured out is how big the difference between the rated power and the maximum power will be, then take a well-known quasi-extended range off-road vehicle as a reference, the rated power of the front and rear motors is 80kW, and the maximum power is 200kW/285kW respectively, the disparity can be seen.
Long-term large-load operation will theoretically cause the motor to overheat, excessive current will even make the motor very hot, and often need high-frequency high-power output when off-road, but the speed is not high enough, and the heat dissipation standard is likely to not meet the needs of the motor when heavy off-road. Then there is a possibility that the windings will overheat and catch fire in the process, so if the off-road vehicle driven by the electric motor is off-road with high load for a long time, the possibility of fire is indeed very high.
Conversely, it is not impossible to solve it.
The main reason for the high temperature of the motor is the long-term high-load operation, so you might as well use the motor with a high enough rated power to solve the problem, but it will increase the manufacturing cost of the vehicle; Therefore, there are also pure electric models in military vehicles, such as Ryoma 2, which is driven by electric motors.
Fuel-powered off-road vehicles aren't perfect, either, and there are risks associated with running at high loads.
If the electric motor is overloaded, it will heat up or catch fire excessively, and the internal combustion engine carried by fuel vehicles also has the same problem; If the engine is running at high revs for a long time, there is also a risk of a cylinder burst, and it is not surprising that an engine burst occurs in heavy off-roading. At the same time, transmissions and transfer cases are subjected to a lot of stress, especially transfer cases, and it is not surprising that the mechanical gears and chain structures used in them are scrapped under high loads.
It is important to note that almost all off-road vehicles have the characteristics of burning engine oil and transmission oil leakage, and the reason for this is precisely the high load for a long time.
Summary:
There is no perfect off-road vehicle, and both fuel and electric vehicles have their own advantages and disadvantages; However, in terms of heavy off-road activities, vehicles with low electric motor power ratings are really not suitable for participation. The reality is that the vast majority of car owners will only light off-road, at best, take a non-paved road, this degree of off-road will not cause the motor to catch fire; Conversely, if you are staring at a large ramp for a long time at a high speed, it is not surprising that the electric motor will catch fire. All in all, the upper limit of both types of off-road drive systems can be very high, but the manufacturing cost of the electric motor four-wheel drive system will be higher if it wants to reach the same upper limit of fuel vehicles; Conversely, due to cost constraints, the upper limit of pure electric off-road vehicles in the same price range is often slightly lower.
The cost advantage determines that fuel-powered off-road vehicles will not be eliminated, and that's it.
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