Drive Principle of Coreless Motors

Coreless motors utilize a coreless rotor structure and electronic commutation (BLDC) technology to directly convert electrical energy into mechanical energy, achieving high efficiency.

1. Core Drive System Components

Coreless motors mainly consist of a permanent magnet stator, a coreless rotor, a commutation system, and position sensors. The rotor employs a coreless design, typically made of enameled wire braided into a cup-shaped structure. The stator uses high-performance permanent magnet materials such as neodymium iron boron (NdFeB).

2. Electronic Commutation Working Principle

The drive controller detects the rotor position using Hall effect sensors or back EMF, precisely controlling the energizing sequence and timing of the three-phase windings. A six-step commutation method (120° conduction mode) or FOC vector control algorithm is used to generate a continuously rotating magnetic field that drives the rotor.

3. Key Performance Characteristics

- Starting Torque: 3-5 times the rated torque at rated voltage

- Speed Range: Typically 8000-50000 RPM (depending on size and design)

- Efficiency Class: Up to 90% or higher (traditional iron-core motors are generally 70-85%)

- Response Time: <10ms (5-8 times faster than iron-core motors)

4. Drive Control Requirements

A dedicated drive chip (such as DRV11873, MC33035) or a microcontroller solution is required, using PWM speed control. Operating voltage is commonly 3.7V-24V, and current varies from 0.5A to 20A depending on size. Overcurrent protection and temperature monitoring circuits are mandatory.

Precautions: Hollow-cup motors may experience axial movement at high speeds (>30000 RPM), requiring the addition of a preload spring or magnetic positioning device. The drive circuit must be properly electromagnetically shielded to prevent high-frequency interference from causing control failure.