New Energy Vehicle Motor Components - Resolver

The resolver, a crucial component in the electric motor assembly of new energy vehicles (NEVs), plays a pivotal role in the powertrain system. Also known as a synchronous resolver or an electrical resolver, it functions as an electromagnetic sensor, measuring the angular displacement and angular velocity of rotating objects. Below is an in-depth introduction to the resolver in the context of NEVs, covering its structure, working principle, and significance.

Structure of the Resolver

The resolver consists of two main parts: the stator and the rotor. The stator, which remains stationary, houses the primary winding. This winding is connected to a high-frequency sine signal, serving as the transformer's primary side and receiving the excitation voltage. The rotor, attached to the motor shaft, includes the secondary winding, acting as the transformer's secondary side. Through electromagnetic coupling, the rotor winding induces a voltage.

Working Principle

The resolver operates on a principle similar to a traditional transformer, but with a key difference. In a conventional transformer, the primary and secondary windings are fixed in position, resulting in a constant voltage ratio between input and output. However, in a resolver, the relative positions of the primary and secondary windings change as the rotor rotates. Consequently, the output voltage varies sinusoidally or cosinely with the rotor's angular displacement.

To obtain the output signal, the resolver employs two secondary stator windings, known as sine and cosine windings. These windings are angularly displaced from each other by 90 degrees. When a high-frequency sine signal is applied to the stator's primary winding, it generates a pulsating alternating magnetic field in the rotor winding. This magnetic field, in turn, induces alternating voltages in the sine and cosine windings. The amplitudes of these induced voltages depend on the angular position of the rotor.

Measurement and Signal Processing

The resolver measures the angular position of the rotor relative to the stator by determining the relative magnitudes of the sine and cosine voltages. As the rotor rotates, the magnetic field's interaction with the sine and cosine windings varies, leading to changes in the induced voltages. These voltage changes are then processed by a resolver digital converter (RDC), which evaluates the current rotor position and rotation speed from the signal curves.

Advantages and Applications

The resolver is highly valued in NEVs due to its robustness, reliability, and environmental resistance. Unlike encoders, which contain electronic components, resolvers have no such parts, making them resilient against contamination, vibrations, and wide temperature ranges. This makes them ideal for applications in harsh environments, such as those found in automotive systems.

In NEVs, the resolver is installed on the motor shaft, providing real-time feedback on the rotor's position and speed. This information is crucial for the efficient and smooth operation of the electric drive system. The resolver's precision and reliability contribute to the overall performance and safety of the vehicle.

In conclusion, the resolver is a vital component in the electric motor assembly of new energy vehicles. Its unique ability to measure angular displacement and velocity, combined with its robustness and reliability, makes it an indispensable part of modern automotive technology. As the automotive industry continues to evolve, the resolver will play an increasingly important role in the development of more efficient, reliable, and environmentally friendly vehicles.