CHAPTER-2 Principle-Operation-Applications of Different ...

1 10 CHAPTER-2 Principle-Operation-Applications of Different stepper Motors and Significance of Permanent Magnet Hybrid stepper motor Introduction stepper motor is defined [1] as a brushless dc motor whose rotor rotates in discrete angular increments when its stator windings are energized in a programmed manner. Rotation occurs because of magnetic interaction between rotor poles and poles of the sequentially energized stator windings. The rotor has no electrical windings, but has salient and / or magnetized poles.

2 A stepper motor moves in increments, or steps, rather than turning smoothly as a conventional motor . The size of the increment is measured in mechanical degrees and can vary depending on the application. A stepper motor is a constant output power transducer and its torque is inversely proportional to the motor speed. In this chapter Different types of stepper motors and their applications are discussed. Here the significance of PMH stepper motor is discussed among other types of stepper motors.

3 Constraints in the design of PMH stepper motor are also discussed. Finally the reasons for the selection of PMH stepper motor for design and how to overcome the constraints in its design are explained. stepper motor Advantages, Disadvantages and applications Advantages and Disadvantages of stepper Motors The Advantages and disadvantages of stepper motor [2] are as mentioned below. Advantages 1. The rotation angle of the motor is proportional to the input pulse. 11 2. The motor has full torque at standstill (if the windings are energized).

4 3. It requires little or no maintenance. 4. It has excellent response to starting/stopping/reversing. 5. It is highly reliable since there are no contact brushes in the motor . 6. The life of the motor is simply dependant on the life of the bearing. 7. The motor s response to digital input pulses provides open-loop control, making the motor less costly and simpler to control. 8. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.

5 9. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses. Disadvantages 1. Resonances can occur in the motor if it is not properly controlled. 2. It is not easy to operate motor at very high speeds. 3. It has limited ability to handle large inertia load. applications of stepper motor stepper motors are used in a wide variety of applications in industry, including computer peripherals, business machines, solar array tracking system, motion control and robotics [2] which are included in process control and machine tool applications .

6 (A) Computer Peripherals Table shows applications of stepper motor for Different computer peripherals like floppy disk, printer, recorder and plotter etc. 12 Table applications of stepper motor for Different computer peripherals Application Use Floppy Disk Position Magnetic Pickup Printer Carriage Drive Printer Rotate Character Wheel Printer Paper Feed Printer Ribbon Wind/Rewind Printer Position Matrix Print Head Tape Reader Index Tape Plotter X-Y-Z Positioning Plotter Paper Feed (B)

7 Business Machines Table shows applications of stepper motor for Different business machines like card reader, copy machine, banking systems, automatic type writers and card sorter etc. Table applications of stepper motor for Different business machines Application Use Card Reader Position Cards Copy Machine Paper Feed Banking Systems Credit Card Positioning Banking Systems Paper Feed Typewriters (automatic) Head Positioning Typewriters (automatic) Paper Feed Copy Machine Lens Positioning Card Sorter Route Card Flow (C)

8 Process Control Table shows applications of stepper motor for Different process control applications like adjustments for air-fuel mixture in carburetor, valve control, process gaze, Bonding, laser trimming etc. 13 Table applications of stepper motor for Different process controls Application Use Carburetor Adjusting Air-fuel Mixture Adjust Valve Control Fluid Gas Metering Conveyor Main Drive In-Process Gazing Parts Positioning Assembly Lines Parts Positioning Silicon Processing I.

9 C. Wafer Slicing I. C. Bonding Chip Positioning Laser Trimming X-Y Positioning Liquid Gasket Dispensing Valve Cover Positioning Mail Handling Systems Feeding and Positioning Letters (D) Machine Tool Table shows applications of stepper motor for Different machine tool applications like milling, drilling, grinding, laser cutting, sewing, mail handling etc. Table applications of stepper motor for Different machine tools Application Use Milling Machines X-Y-Z Table Positioning Drilling Machines X-Y Table Positioning Grinding Machines Down-feed Grinding Wheel Grinding Machines automatic wheel dressing Electron Beam Welder X-Y-Z Positioning Laser Cutting X-Y-Z Positioning Lathes X-Y Positioning Sewing Chip Positioning 14 Types of stepper Motors stepper motors are classified according to their rotor design and stator winding

10 Type [3-10]. There are three basic types of stepping motors according to the rotor design, namely variable reluctance stepper motors (VR), permanent magnet stepper motors (PM) and permanent magnet hybrid (PMH) stepper motors. Permanent magnet motors have a permanent magnet rotor, while variable reluctance motors have salient pole soft-iron rotors. Hybrid stepping motors combine features of both permanent magnet and variable reluctance motors technology. Both permanent magnet and hybrid stepper motors are classified according to their stator winding as unipolar winding motors, bipolar windings motors and bifilar winding motors.