What does dtr mean in a car

Understand the performance of an electric motor

How do you describe the power output of car engines?

In physics, power output refers to the amount of energy that is given off in a certain period of time. Applied to the automobile, it describes the amount of mechanical energy that is generated by the engine, again within a certain time frame. It affects the vehicle's acceleration, traction (the weight it can move), and its ability to go uphill.

Regardless of whether it is an internal combustion engine or an electric motor, the performance of the mechanical energy relates to the product of speed (measured in revolutions per minute) and torque. Expressed in Newton meters (Nm), the torque describes the pulling power of the engine.

This takes into account the fact that two engines with the same power behave differently and can feel very different to the driver. A sports car delivers a performance that cannot be compared to that of a large truck, even if both have the same engine power!

How do you calculate the power that an electric motor delivers?

A vehicle manufacturer cannot simply specify the engine power: it is measured in a test procedure and is expressed in the change in torque as a function of speed. The value used by automobile manufacturers generally refers to the maximum measured power. It is given in watts (W) and more generally in kilowatts (kW).

How to determine the power of an electric motor

When it comes to an electrical system like the one in an electric vehicle, mechanical power - expressed in watts (W), kilowatts (kW), or horsepower (HP) - is calculated by dividing the speed (rpm) with the torque (dem The rotational equivalent of the linear force, measured in pound feet (lb-ft) or newton meters (Nm)) is multiplied. But before you get into tedious calculations, there are a number of websites on the Internet where you can simply enter the speed and torque of your electric vehicle in order to calculate the power in kilowatts. Or you can refer to the operating instructions for your vehicle.

How are kilowatts (kW) and horsepower (PS) related?

“Horsepower” traditionally describes the performance of a car engine. The name comes from the late nineteenth century. In this way, the power output was equated with a workload that people know and can therefore understand more easily. The horsepower, abbreviated as PS, describes the power a horse has to lift a 75 kg weight one meter high in one second. According to the metric system, it corresponds to about 736 W.

The engine output of an electric vehicle can therefore be given in kW or PS. The R135 engine in the ZOE, for example, generates an engine output of 100 kW, i.e. 135 hp - hence the name! Its torque has been increased to 245 Nm, compared to 225 Nm for the R110 engine introduced in 2018. This makes the ZOE more dynamic when overtaking or merging into motorway traffic.

Which factors determine the power output of an electric car?

The job of a motor is to generate mechanical energy from another energy source. So its performance is derived from its maximum energy conversion capacity. In the case of an electric vehicle, the power depends on the size of the motor (its volume) and the wattage of the incoming current.

What is the “usable” energy output of an electric motor?

The power output is the ability of a motor to convert supplied electricity into mechanical energy. The more energy that can be converted, the more efficient the motor.

Not all of the energy provided by the power grid or the charging station is ultimately used to drive the motor. It can be lost along the way through heat or friction. In other words: the mechanical energy actually used by the motor is the usable energy. If you divide the actual power of an electric motor by the ideal power (equal to the initial power consumption), you get the mechanical efficiency of the motor.

For an electric vehicle, the “usable” energy can be calculated by dividing the output power (speed x torque) by the input power and expressing the result as a percentage. This is also known as the efficiency formula r = P / C, where P is the amount of useful power (“product”) produced per amount C (“cost”) of resources consumed.

So the goal is to reduce this power loss in order to achieve maximum efficiency. In this way, most of the energy stored in the battery is used to increase the range of the electric vehicle. In this regard, the ZOE does particularly well. With a WLTP * range of 395 km thanks to a 52 kWh battery, it offers one of the best conditions on the electric vehicle market across all segments.

Performance, consumption and range

However, the maximum power output has no direct influence on the range of an electric car - the driving style has a much stronger effect here. So it's not about the most efficient electric car engine, but about the most efficient driving behavior. Strong acceleration for example to an increase in electricity consumption. Even high speeds put a considerable strain on the battery. And the higher the speed, the more energy it takes to keep it going.

Conversely, a relaxed driving style keeps current consumption low and makes regenerative braking more effective. This is the principle of eco-driving - one of the best ways to increase the range of an electric car.