Unquestionably, electric vehicle is the present buzzword in the automotive industry. You may not own one yet, but a growing number of car enthusiasts are buying these vehicles. The main reasons behind this increasing popularity include low-cost driving experience, tax savings, environmental benefits and practicality. But you may ask what will happen in the future when leases expire?
Purchasing an electric car is certainly a big investment and every owner wants the vehicle to last long. However, the life expectancy of an electric vehicle mainly depends on three components – motor life expectancy, battery life expectancy, and life expectancy of some other components.
Different types of electric motors are used in an electric vehicle – from permanent magnet synchronous motor to AC induction motor to reluctance motor to DC motor. However, AC induction motors are most commonly used in electric vehicles. Advancements in the field of speed control using power electronics components have greatly contributed in making them a preferred choice of electric automotive manufacturers.
The life expectancy of an electric car motor depends on different types of factors. These include:
These are just the key factors that affect the performance of an electric vehicle motor.
However, in general, an electric car motor can last for more than 15 to 20 years, provided it performs within the limits of specified values and at normal operating conditions.
Advancements in the field of motor analysis tools have made it extremely easy to make critical maintenance decisions by simplifying the process. Electric motors convert electrical power to mechanical forces, which are critical for the propulsion of an electric vehicle. Proper measurements of these forces like speed, torque, mechanical power etc can give you a good understanding of the reasons behind the poor performance of an electric motor. Let’s have a quick look at how the above forces influence the efficiency of the motor.
Torque refers to the amount of rotational forced generated by a motor. A motor’s torque is one of the most critical variables that characterize instant mechanical performance. Measurement of torque can offer a clear insight into the condition of the motor including the load. It’s crucial to ensure that the motor is running at the specified torque level to provide you with reliable operation and minimized maintenance costs.
Power anomalies like unbalance, harmonics, transients etc can trigger critical damage to the motor of an electric vehicle. Unbalance, which can occur in both current and voltage, often leads to long-term wear like burnt windings and elevated motor temperature. Harmonics that create distortion of both current and voltage can cause motors to run hot, which in turn can lead to overheating or even motor failure. Motor insulation can be severely damaged and over-voltage circuits can be tripped by transients.
Mechanical overload conditions can trigger stress to motor components like insulation, couplings, bearings etc, which can lead to decreased efficiency and premature failure. By identifying faulty or poorly performing motors and repairing them, you can keep both efficiency and energy consumption in check.
Though all electric motors come with predetermined lifespan, it depends on proper maintenance to a great extent. Without proper maintenance, electric vehicle motors can break down much quicker than expected. This makes it crucial to have a good understanding of the key causes of motor failure to bring down the risk of failures, which will keep the motor in a position of attaining its maximum possible lifespan. Let’s have a look at such key causes.
Contamination from chemicals, dirt and dust is one of the major causes of motor failure. Foreign particles that find their way inside a motor can weaken bearing balls and raceways, which can lead to high levels of wear and vibration. The cooling fan can also get blocked, which limits the ability of the motor to regulate its temperature, thus increasing the likelihood of overheating.
A significant percentage of insulating failures in electric motors happen due to overheating. Overheating can be triggered by a high temperature operating environment or poor power quality. Failing to keep the motor cool will increase the risk of breakdowns to a good extent.
Vibration can lead to a diverse range of issues with the motor and can gradually cause the motor to fail prematurely. Often, vibration is caused when the motor is improperly positioned on an unstable or uneven surface. However, in electric vehicles, vibration can also be the outcome of an underlying issue with the motor like corrosion, misalignment etc.
Low resistance is another common reason of motor failure. It’s often caused by the degradation of the windings’ insulation due to conditions like physical damage, corrosion, and overheating, among others. This results into inadequate isolation between the motor windings or conductors that can cause short circuits and leakages, and eventually, motor failure.
In the event of an excessive amount of current flow through the motor windings that exceeds the specified amount which the motor is able to carry safely and efficiently, electrical overload starts to occur. This can be triggered by a low supply voltage that can result into the motor drawing excess amount of current in an attempt to maintain its torque. An excessive voltage supply and short circuited conductors are two other factors that can cause electrical overload.
If you’re thinking of car conversion, selecting the right electric motor that can be fitted into a particular vehicle is immensely important to optimize its life expectancy. The right motor can give you the desired vehicle performance in a cost-effective way. In order to find the right motor, you need to identify the most demanding requirements of the car. Here, we’ve outlined some key tips that can help you sail through the process efficiently.
Properties of your intended electric vehicle like weight, size, aerodynamics, overload etc. are crucial car characteristics that will determine torque, power, and speed requirements of your electric motor. Having a good understanding of these aspects would not only help you in handling different operating conditions but even play a crucial role in the selection of the right motor too.
Identify the targeted maximum speed of your car together with the available gear box ratios (if there’s one) and the differential ratio. Also, consider the rolling radius of the wheels when performing calculations to chalk out the maximum speed the motor would be required to reach.
Try to chalk out the highest grade your car will need to ascend. With the help of that grade, you can calculate the highest torque required by your electric motor. Remember to take maximum weight under consideration as well.
Sometimes, you can find maximum power simply at the maximum speed. However, this also translates into having a motor sufficiently powerful to be able to go through varied conditions that the car can be submitted to. The maximum power lets the car reach as well as maintain a constant speed under stringent speed and slope conditions. You need to consider the duration of the condition as well. Contrary to ICEs (internal combustion engines), the maximum power of an electric motor can’t be continuously sustained and it would lead to over engineering if you want the electric motor to perform at its optimum without any time constraints.
How you will use the electric car also plays an important role in determining the right motor. What will be the normal driving cycles of the car? Will it be driven frequently on long distances with a limited number of stops? Or, will it be driven mostly in the urban area with a lot of stops? Try to figure out all these to determine the vehicle configuration (all electric, parallel hybrid, series hybrid etc.) as well as the battery pack side you’d require to finalize your choice of the electric motor.
Horsepower is used to measure the power output delivered by an electric motor. When an automaker states that one of their gasoline-power is capable of delivering 300 horsepower, it’s actually referring to the peak horsepower. This number refers to the highest amount of power that the engine can deliver at a specific number of RPM (revolutions per minute). The downside of a gas engine is that it must develop RPMs through acceleration before it reaches its maximum torque and power. On the contrary, as electric vehicles have the power available immediately, massive horsepower figures may not be required. For example, the Tesla Roadster S is almost as fast as the Corvette Z06 with about half its horsepower. In addition, the driving experience also becomes quieter, smoother, and possibly, with less maintenance as an electric motor comes with a significantly fewer number of moving parts compared to an internal combustion engine.
If you are also interested in how do electrical vehicles work, read our another article, written about this.
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