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Designing Induction Motors

Motors and generators with MotorSolve

MotorSolve IM is a comprehensive tool within which modeling, design iteration and design validation can be carried out for induction machines. To facilitate this, user friendly and powerful modeling features as well as multiple types of analysis options of varying degrees of approximation and complexity have been implemented. These include equivalent circuit based analysis, AC analysis, PWM and dynamical motion simulations. Provided below is a summary of MotorSolve IMs' modeling and analysis capabilities.

MotorSolve IM for Induction Motors

METHODS and RESULTS

MODELING and SIZING the MOTOR

Models in MotorSolve IM can be created in as few as four easy steps (drive, rotor, stator and winding specifications) that is numerical input based and does not require any drawing. A variety of stator and rotor cage geometries are supported in MotorSolve IM. Significant modeling features include output based sizing, automatic winding layout generation, a library containing over 200 materials, user defined material modeling with advanced core loss computations, detailed end effect, overhang modeling, and skewing among many others.

The figure to the left shows the sizing module interface and the automated coil winding editor of a 17 bar-24 slot 500W induction machine designed using MotorSolve IM.

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TORQUE-SLIP CHARACTERISTIC of the IM

MotorSolve IM is a FEA based analysis software. Its four analysis options can accurately model various induction motor related parameters and effects such as leakage inductance, slotting, deep bar effect, skewing, effects of switching on motor characteristics due to inverter fed phases, etc. The interface allows the user to compute the machine characteristics at various speeds (and other variables) as well as those at a single operating point. An example of this shown in the figure on the left, which shows the torque-slip characteristics of a 17 bar-24 slot squirrel cage machine at various synchronous speeds. Following is a brief summary of MotorSolve IMs' analysis options.

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EQUIVALENT CIRCUIT PARAMETERS of the IM

Equivalent circuit parameters and machine characteristics of induction machine models are available in MotorSolve IM with just a click, an example of which is shown here. The circuit parameters are determined from locked rotor and no-load settings using IEEE standard guidelines. Note that core losses are taken into account in the equivalent circuit computations. Also, leakage due to stator and rotor slots, belt and zig zag, etc. are lumped together.

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MACHINE CHARACTERISTICS using EQUIVALENT CIRCUIT ANALYSIS

An example of the machine characteristics using equivalent circuit based analysis is shown in the figure to the left.

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GREATER PRECISION with AC ANALYSIS

AC analysis is the second of four analysis types in MotorSolve IM. This method differs from equivalent circuit calculations in that variations of the circuit parameters with slip are taken into account in addition to material non-linearities. Hence, machine characteristics and losses are predicted with greater precision. An example of the hysteresis and eddy current losses as well as shaded plots of the hysteresis loss, computed using AC analysis, is shown in the figure to the left.

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EFFECTS of SWITCHING on the MACHINE PERFORMANCE

PWM analysis is important for studying the effects of switching on the machine performance. The complete 3-phase bridge circuit equations are solved in PWM taking mutual and self couplings into account. Delta and space vector modulation simulations can be carried out by MotorSolve IM. An example of the bar currents computed using PWM simulations is shown here.

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COMPLETE MOTION SIMULATION of the MOTOR

This type of analysis carries out complete FEA-based dynamical simulation of the model. This feature allows the user to validate a model and/or fine tune a design. An example of transient simulation results of a model, in which the output torque is compared for various rotor bar conductor areas, is shown in the figure to the left.

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