As described in Chapter 1, there are several types of stepping motors.
Since stepping motors can be easily controlled using digital signals, they are used in various applications, including not only industrial equipment and PC peripherals but also fax machines, copiers, and other types of office equipment.
Stepping motors have the following features:
- <1> Switching the coil current moves the motor by the predetermined angle.
- <2> Feedback signal is unnecessary.
- <3> Positioning errors do not accumulate.
- <4> Good compatibility with digital control systems makes it easy to build control circuits.
Permanent-magnet stepping motors generate large torque in relation to their size. And VR (variable reluctance) motors that do not use permanent magnets are good at dividing a round into small portions. VR motors and permanent-magnet motors are used in special applications.
The hybrid type, also known as the HB type, was invented to combine advantages of the above two types. The structure of a HB type motor was introduced in Fig. 1.29 of Chapter 1.
The claw-pole PM type (to be described later) is one of the HB type motors rather than the permanent-magnet type.
Although this motor cannot divide a round into many portions, it is compact and reasonably priced. As a result, it is primarily used in small machines.
This chapter describes the HB type and claw pole type PM motors that are today's mainstream stepping motors.