In this paper, the impact of the DC bus voltage on the iron losses of a permanent magnet synchronous motor (PMSM) fed by a pulse-width modulation inverter is evaluated. Under constant speed operation, the modulation index decreases when the DC bus voltage increases. This modifies the harmonic content of the PMSM input voltage and then affects the motor iron losses. The experimental measurements results show that, for the conditions considered in this paper, the total iron losses are 1.8 times larger at the lowest modulation index than at the highest one.
The output torque of a three-phase interior permanent magnet synchronous motor (IPMSM) can be controlled within its allowable range using a pulse-width modulation (PWM) DC-AC inverter. In this paper, the effect of load torque on the iron losses of an IPMSM is studied by considering three different driving conditions, namely no-current, noload, and load conditions. In order to perform a careful evaluation in the experiments, the motor is tested at various rotational speeds, namely 750 min −1 , 1500 min −1 , and 2250 min −1 ; the voltage modulation index of the PWM inverter and the load torque are also varied. The experimental results in all the test cases show that the iron losses of the motor vary when the excitation condition is varied among the no-current, no-load, and load cases. Furthermore, a three-dimensional (3D) finite element analysis (FEA) is performed for the main test case when the motor is operated at the rated speed of 750 min −1 for reference purpose. The harmonic components caused by the excitation inverter in the stator voltage, current, and magnetic flux density are found to be the main reasons for the increase in iron losses of the motor in the no-load and load conditions compared to the no-current condition; an increase in torque also causes a relatively significant increase in the iron losses.Keywords: finite element analysis, interior permanent magnet synchronous motor, iron loss, PWM inverter, effect of load torque
This paper presents the harmonic analysis of various pulse width modulation strategies used for the DC-AC converters. An efficient harmonics computation algorithm for piecewise continuous periodic waveforms has been derived. Fourier coefficients of experimentally obtained waveforms or simulation results can be cal; culated efficiently. Harmonic performance analysis of natural sampling modified subharmonic control, symrnetric/asymmetric uniform, sinusoidal pulse width modulation, and pulse position modulation strategies have been studied. Results can be used as guidelines for the modulation strategies selection in the PWM inverter design.
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