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2 Phase 4 Pole Permanent Magnet Stepper Motor:

Figure 10.39 shows the phases (stacks) of a 2 Phase 4 Pole Permanent Magnet Stepper Motor. The rotor is made of ferrite or rare-earth material which is permanently magnetized. The stator stack of phase b is staggered from that of phase a by an angle of 90° elect. When the phase a is excited, the rotor is aligned as shown in Fig. 10.39(a). If now the phase b is also excited, the effective stator poles shift counter-clockwise by 22 1/2 ° [Fig. 10.39(b)] causing the rotor to move accordingly. If the phase ‘a’ is now de-energized (with b still energized), the rotor will move another step of 22 1/2 ° . The reversal of phase a winding current will produce a further forward movement of 22 1/2 ° and so on. It is easy to visualize as to how the direction of movement can be reversed.

2 Phase 4 Pole Permanent Magnet Stepper Motor

To simplify the switching arrangement, which is accomplished electronically, double coils are provided for each phase. The schematic diagram of switching circuit of 2 Phase 4 Pole Permanent Magnet Stepper Motor is shown in Fig. 10.40.

2 Phase 4 Pole Permanent Magnet Stepper Motor

Application:

Compared to variable-reluctance motors, typical permanent-magnet stepper motors operate at larger steps up to 90°, and at maximum response rates of 300 pps.