Lect 7 The Stepper Motor This motor called

• This motor called “stepper” due to its behavior, that it moves in

1. Printers. 2. Plotters. 3. High-end office equipments. 4. Hard disk drives. 5. Medical

• An open loop control drives. • Accurate, precise, reliable and repeatability of

The Construction of Stepper Motor As it mentioned before that there are three types

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Lect. 7 The Stepper Motor

• This motor called “stepper” due to its behavior, that it moves in steps. This machine can be classified as a Reluctance Motor or sometimes as a Permanent Magnet Motor, and one of its types is the Hybrid Stepper Motor due to the mixing between the usage of cores of reluctance type and permanent magnet type in the construction of its rotor. • Hence, there are three types of this motor: The Variable Reluctance type, The Permanent Magnet Type, and The Hybrid Type. • But as it is well known that both of the PMM and RM can move in steps when their stator winding composed of salient poles and fed by DC voltage through electronic switches. • So, what is new in this type of machines? The main idea of manufacturing this type of motor, is the load requirements in the following applications:

1. Printers. 2. Plotters. 3. High-end office equipments. 4. Hard disk drives. 5. Medical equipments. 6. Fax machines. 7. Automotive. 8. Robotics. 9. And many more. Now you have to think about the common requirements of these equipments! It is clear that they need a machine able to furnish the following: • Ease to control rotation angle, speed, position and synchronism. • A low power and low cost and small volume drives.

• An open loop control drives. • Accurate, precise, reliable and repeatability of movement drives. The above requirements lead to create the stepper motor. Hence, this motor is a new technology (but not a new idea) machine. It has special characteristics to be used in such applications. In order to study this machine, its construction and principle of operation must be studied.

The Construction of Stepper Motor As it mentioned before that there are three types of this motor: Variable Reluctance (VR) Motor: • It composed of a soft iron multi-toothed rotor and salient wound stator. • When the stator windings are energized with DC current the poles become magnetized. • Rotation occurs when the rotor teeth are attracted to the energized stator poles.

Multi-stack variable-reluctance motor