Electric motors for utility vehicles and ships

Electrical mobility – What are the advantages over combustion engines?

The great disadvantage of combustion engines is that their optimum efficiency is only valid for a very narrow operating point, which is usually at maximum power. Using so-called clam charts for combustion engines, the efficiency can be represented as a function of load and speed. This shows that the efficiency can fall to 15% at half load – and decrease even further with lower loads.

 This circumstance makes combustion engines extremely inefficient in partial-load operation. When they are compared to electric motors, which can adapt their power very dynamically to the respective load cycles and only have to put up with minor losses, it immediately becomes clear that electric motors not only have lower emissions but are considerably more efficient, above all with changing load cycles. In addition, the energy that is generated during braking is not converted into heat but is at least partially retained in the system due to recuperation and is thus returned to the battery. Efficiencies of up to 98% can therefore be achieved in electrical drive systems with an optimally adjusted electric motor and inverter.

Furthermore, the field weakening of the electric machines offers excellent possibilities for eliminating switchable transmissions. In this way, currents in the stator can be used to reduce the magnetic flux between the rotor and the stator in order to change the torque constant. Higher rotational speeds can thus be achieved at lower torques with the same terminal voltage.

Depending on the motor topology, the system can be overloaded by up to 300% during ascents or start-up. The ratio of the maximum to the minimum gear reduction can be increased by a field weakening, resulting in cost savings for the inverter at a lower total cost.

Various motor topologies for electric motors

It is very important to integrate the right motor for the entire system. For this reason, ARADEX offers various motor topologies. To meet the requirements of the different traction, propulsion, and function drives, ARADEX offers various synchronous and asynchronous motors.

• Permanent magnet synchronous motors (also called PM motors): These are single-phase or three-phase motors in which a rotor is moved synchronously by a magnetic rotating field in the fixed part, the stator. During operation, the movement of the PM motor and AC voltage is synchronous. PM motors are a combination of a brushless direct current motor and an alternating current asynchronous motor. The stator, which is equipped with a rotor and coils, produces a sinusoidal flux density similar to that of an asynchronous motor in the air gap of the machine. However, no stator current is used to generate the magnetic field, which results in the power density of PM motors being higher than that of an induction motor at the same current. Furthermore, they are lighter and have a lower moment of inertia.

PM motors are particularly suitable for applications with high capacities and small construction volumes, such as, e.g., in aviation, industrial automation, and race cars

• Asynchronous motors: Asynchronous motors are motors with a rotor (consisting of the stator plate that holds the rotor and the metal bars) that runs asynchronously with the rotating field. With induction motors, which include asynchronous motors, the voltage generated by the rotor is induced via the magnetic field of the stator. Asynchronous motors are often used in drive technology because they are extremely robust, require little maintenance, and are simple and inexpensive to manufacture. At ARADEX, asynchronous motors are used as direct drives, which means that efficiency losses can be avoided. However, asynchronous motors are larger and require more space as a result. For this reason, they are primarily used in large systems, such as trucks.

We will be happy to advise you in order to find the best motor for your application.