Different types of motors have different requirements for magnet materials due to their different requirements and environments. The following is a three-part description focusing on DC motors, asynchronous motors and stepper motors.
Direct Current Motors (DC Motors):
Permanent Magnet DC Motors: These motors typically use permanent magnet materials as the excitation source, requiring high magnetization strength and stable magnetic properties to ensure efficient motor operation. Commonly used permanent magnet materials include permanent magnet ferroboron (NdFeB) and permanent magnet samarium cobalt (SmCo).
Excited DC motors: The magnetic field of these motors is supplied through an external power supply, and a common electromagnet can be used as the magnetization source. The requirements for magnetic materials are lower, but good permeability and saturation magnetic induction are still needed.
Alternating current motors (AC motors)
Asynchronous motors (induction motors): These motors do not require permanent magnet materials and mainly require core materials with high permeability and low hysteresis loss to minimize energy loss and improve efficiency. Silicon steel sheet is the commonly used core material.
Synchronous motors: For some applications that require matching with an external synchronization signal, synchronous motors usually require permanent magnet materials to generate a stable magnetic field.
Permanent magnet stepper motors: similar to permanent magnet DC motors, permanent magnet stepper motors require the use of permanent magnet materials with high magnetization strength to ensure accurate stepping motion.
Hybrid stepper motors: These motors combine both permanent magnet and electromagnetic excitation, and the requirements for magnetic material and number of magnetization poles depend on the specific design.
When we talk about the number of poles in general, it refers to the multi-pole magnetization of the motor. For magnetic rings, 2-pole magnetic rings are mostly used for small DC motors, and some of them will have 4 poles. And the magnetic rings used for stepper motors, brushless motors, synchronous motors have 4, 6, 8, 10, 12 .... Even number of poles.
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