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PWM analysis of an Induction Motor

Motors and generators with MotorSolve

The PWM feature of MotorSolve IM is designed to assist the machine engineer to gauge the performance of induction motors for realistic drive circuits. To this end, 3-phase bridge circuits with delta and space vector modulation (with Wye/Delta connection) options are offered that allow the user to calculate a large array of entities and compare results with ideal drive simulation. The methodology and some examples of results using PWM simulations are presented in this application page.

PWM analysis in MotorSolve IM

METHODS and RESULTS

SETTING UP a PWM ANALYSIS

The PWM simulation feature of MotorSolve IM is based on a system matrix model of the circuit equations, which take into account the self and mutual inductances between the stator windings and rotor bars. The inductance and resistance matrices are calculated based on finite element analysis solves and the model is quasi-linear. MotorSolve IM supports both current and voltage driven simulations which are implemented using delta and space vector modulation, respectively.

Results can be obtained as a waveform, time averaged or in terms of their harmonic contents. The user can set the simulation operating point as well as the resolution and accuracy of the simulations. The interface of the PWM simulation of MotorSolve IM is shown on the left.

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PHASE CURRENT MODULATION

The delta modulated simulation is used to carry out current driven PWM. A current hysteresis level, set as a percentage of the rated current, is used to control the duty cycle for the switches. An example of phase current modulation for a 24 slot - 17 bar machine is shown here.

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PHASE CURRENT MODULATION

Phase current modulation: 24 slot - bar numbers 1, 3, 5, and 7

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SPACE VECTOR MODULATION

The option presented here allows the user to carry out voltage driven modulations. The switching frequency is set by the user based on which the voltage in the circuit is regulated. An example of the voltage regulation is shown in the figure to the left.

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END RING CURRENT

Space vector modulation - end ring currents

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