What are the differences between PM and VR and Hybrid stepper motors?
A PM motor, short for permanent magnet stepper motor, uses permanent magnet steel in its rotor. The stator of PM motor is manufactured with claw-shaped tooth poles through stamping, while the rotor uses radial multi-pole magnetized permanent magnet steel. Operating Principle: The magnetic field generated by the direction of coil current interacts with the rotor magnetic field through mutual repulsion, causing the motor to rotate forward/reverse. VR Motor: A VR stepper motor features teeth on both the rotor and stator, where magnetic force is concentrated. Most cores use ferromagnetic materials such as iron, which it is abundant and facilitates the easy passage of magnetic flux. Unlike other types, VR stepper motors lack magnets, which means they cannot provide holding torque or braking torque when stationary. HB Motor: A hybrid stepper motor is a combine the design and advantages of both permanent magnet and variable reluctance stepper motors. Consequently, a hybrid stepper motor incorporates a permanent magnet rotor along with a toothed rotor and stator. Equipped with strong permanent magnets, toothed rotors and stators, and a minimal air gap, hybrid stepper motors concentrate magnetic flux more effectively than the other two types. By stacking magnetic laminations, these motors achieve low losses, allowing magnetic flux to pass through easily. Permanent Magnet Vs Variable Reluctance Vs Hybrid Stepper Motors:
| Characteristic | Permanent Magnet stepper motors | Variable Reluctance stepper motors | Hybrid stepper motors |
| Cost | Relatively Cheap | Moderate | Relatively expensive |
| Design | Moderate | Simple | Complex |
| Resolution | step angle: 3°~30° | step angle: 1.8°, 0.9° and smaller | step angle: 1.8°, 0.9° and smaller |
| Speed Torque curve | High Torque at low speed, more pronounced torque drop at high speed | Less pronounced torque drop at high speed | High Torque at low speed, more pronounced torque drop at high speed (Maximum torque at the same speed) |
| Noise | Quiet | Noisy | Quiet(quieter if using microstepping) |
| Heat | Low temperature rise | High temperature rise(Need heat sink) | Low temperature rise |
| Microstepping | Full, Half and Microstepping | Typically run in Full-Step only | Full, Half and Microstepping |
| Rotor material | Ferrite magnet or NdFeB | Silicon steel sheet or iron(Non-permanent magnet) | NdFeB |