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Stepped Tooth Configuration For Stepper Motors

IP.com Disclosure Number: IPCOM000051548D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Chai, HD: AUTHOR [+2]

Abstract

It is well known that optimum stepper motor performance is obtained when the valley-to-tooth ratio (W(v)/W(t)- see Fig. 2) is in the neighborhood of 1.5. As a consequence, a greater number of step motors having small step angles, on the order of 2 degrees, are designed around this ratio. However, for motors having large step angles, the use of this ratio introduces a negative factor into motor performance. This factor can be eliminated by the use of the tooth configuration proposed below.

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Stepped Tooth Configuration For Stepper Motors

It is well known that optimum stepper motor performance is obtained when the valley-to-tooth ratio (W(v)/W(t)- see Fig. 2) is in the neighborhood of 1.5. As a consequence, a greater number of step motors having small step angles, on the order of 2 degrees, are designed around this ratio. However, for motors having large step angles, the use of this ratio introduces a negative factor into motor performance. This factor can be eliminated by the use of the tooth configuration proposed below.

A typical three-phase step motor assumed to have a large step angle is schematically shown in Fig. 1. The step angle is 10 degrees. Because of this large step angle, each stator pole 2 contains only one tooth about which the coils 4 are wound. In Fig. 1, only the phase A windings are shown for the sake of clarity.

Fig. 2 illustrates an enlarged view of the case where the valley-valley to-tooth ratio is 1.0. As mentioned previously, this is not the optimum ratio. It will, however, prevent the poles from saturating early due to the larger pole cross- section. Fig. 3 depicts an enlarged view of the situation where the valley-to-tooth ratio is the optimum 1.5. Unfortunately, because of the narrower pole width, the poles will saturate earlier, resulting in a reduction of flux through the working gap. This, in turn, reduces the maximum holding torque that can be attained.

Our proposed arrangement for avoiding this dilemma is shown in Fig....