Optimized design of single phase induction motor
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Date
2013
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University of Management and Technology
Abstract
This thesis presents a design methodology and software design tool, which are useful for the design of induction motors and synchronous generators. A user or designer specifies performance requirements and the system synthesizes a set of design parameters which meet those specifications. Optimization may also be performed by the designer with respect to any performance parameter, while keeping other requirements within specified limits.
Electric machine design is in general a "hard" problem, and most designers rely on their knowledge, experience, and intuition to design new motors or modify existing ones.
Most of the problems encountered can be traced to non-linearity, coupled equations, categorical variables, and presence of multiple objectives. Analysis of given design variablesto compute performance parameters are comparatively easier using circuit equation analysis routines. The converse (synthesis process), where we need to generate a set of design variables matching certain performance criteria, is a much harder problem. This is also the more common problem in a design scenario. We propose a two-step methodology to generate designs matching user requirements, and perform optimizations.
In the first step of our methodology, a Monte-Carlo based statistical approach is proposed to circumvent the aforementioned problems. The n-dimensional design space is first reduced to a smaller sub-space which is more likely to contain the desired solutions. A multivariate normal distribution is used to characterize this sub-space. Several designs are generated within this sub-space which allows a user to evaluate multiple design possibilities. All of these designs meet user requirements.
These designs are then also used as starting points for further optimization, in the
second step of our methodology. A statistical function approximation tool called MARS
(Multivariate Adaptive Regression Spines) is used to "map" the relations between inputs
and every performance variable. This map is then used during the optimization process
for obtaining function values and gradients at all locations. A non-linear programming
algorithm is used to perform all optimizations. Ideas from multiple objective optimization
literatures are used to account for multiple performance variables.
The proposed methodology is implemented in an industrial strength software system
which allows a firm to perform multiple scenario analyses, automate the design process, perform optimizations, shorten development lead times, and react fast to customer requests.
Several examples using industrial strength circuit analysis routines are presented, and their results analyzed.
Even though this approach is applied to the case of induction motors, and synchronous
generators, it is believed that the methodology is sufficiently general, and would be applicable to many design situations.
There are probably more single-phase ac induction motors in use today than the total of all the other types put together.
It is logical that the least expensive, lowest maintenance type of ac motor should be used most often. The single-phase ac induction motor fits that description.
Unlike polyphase induction motors, the stator field in the single-phase motor does not rotate. Instead it simply alternates polarity between poles as the ac voltage changes polarity.
Voltage is induced in the rotor as a result of magnetic induction, and a magnetic field is produced around the rotor. This field will always be in opposition to the stator field (Lenz's law applies). The interaction between the rotor and stator fields will not produce rotation, however. The interaction is shown by the double-ended arrow in figure 4-10, view A. Because this force is across the rotor and through the pole pieces, there is no rotary motion, just a push and/or pull along this line.
There are several types of single-phase induction motors in use today. Basically they are identical except for the means of starting. Once they are up to operating speed, all single-phase induction motors operate the same.
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Keywords
single phase, induction motor