Servo Drive Research Paper

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There are a variety of ac servo drives available on the market competing with both the dc brush machine and other ac servo drives. The selection process of a servo drive for a particular application in the fractional to 30-hp range can be represented by Fig. 4.1. From Fig. 4.1, it is clear that the first decision to be made for the selection of the motor is whether to use a dc brush or a brushless servo. The reasons for choosing brushless servo motor drives over the brush type dc motor drives are well known and include robustness, higher torque speed bandwidths lower maintenance The mechanical commutator and brushes of the dc motor also enforce severe limitations on its maximum speed and overcurrent capabilities. Assuming that it …show more content…

In the surface-mounted machine, two variations can exist. The magnets can be inset into the rotor or project from the surface of the rotor. These machines will be referred to as buried, inset, and projecting PM machines, respectively. Buried PM machines are more difficult to construct than either the inset or projecting surface-mounted machines. In addition, epoxy glue is used to fix the magnets to the rotor surface in the inset and projecting surface-mounted machines. This implies that the mechanical strength of the surface mounted machines is only as good as that of the epoxy glue, assuming no retaining sleeve is used; hence, buried PM machines are more robust and tend to be used for high-speed …show more content…

Hence, the third phase current can always be inferred from the other two phases. Parameter Sensitivity Parameter changes in all electrical machines occur due to changes in temperature, current level, and operating frequency. In permanent-magnet machines, an increase in temperature results in a partial loss of flux density of the permanent magnets and an increase in stator resistance. If the permanent-magnet machines are rated at the maximum operating temperature, then at ambient temperature, higher than rated output would be obtainable due to the increase in flux density relative to the rated conditions. Conversely, if the machine is rated at ambient temperature, the output at elevated temperatures would be reduced. Higher-than-rated current values saturate the machine inductances. The saturation of the leakage inductances would cause a reduction in their value, thus allowing a greater potential difference between the dc bus and the back emf and, hence, providing greater current

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