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A Calculation Method of Iron Loss Resistance of Variable-Frequency Motors Considering PWM Harmonics

A variable frequency motor and calculation method technology, applied in the direction of measuring resistance/reactance/impedance, measuring electrical variables, and measuring dielectric properties, etc., can solve the problems of slow calculation speed and achieve the effect of convenient loss

Active Publication Date: 2021-03-16
XI AN JIAOTONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

But the model is based on the finite element method, so the calculation speed is still very slow

Method used

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  • A Calculation Method of Iron Loss Resistance of Variable-Frequency Motors Considering PWM Harmonics
  • A Calculation Method of Iron Loss Resistance of Variable-Frequency Motors Considering PWM Harmonics
  • A Calculation Method of Iron Loss Resistance of Variable-Frequency Motors Considering PWM Harmonics

Examples

Experimental program
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Effect test

Embodiment 1

[0118] With a 5.5kW variable frequency induction motor, its parameters are shown in Table 1 respectively. Under rated conditions, the voltage and current waveforms of the two motors are as attached figure 2 shown. Utilize the solution method of the iron consumption resistance that the present invention proposes, calculated its iron consumption resistance with the change situation of the modulation coefficient of rotating speed and PWM frequency converter as attached Figure 4 . Among them, the switching frequency of the inverter is 5kHz. When the speed is lower than the rated synchronous speed, the ratio of the induced potential to the frequency is guaranteed to remain unchanged; when the synchronous speed exceeds the rated synchronous speed, the induced potential is taken as a constant value. It can be seen that the higher the modulation coefficient of the PWM inverter, the higher the speed of the induction motor, and the greater the equivalent resistance of the iron loss....

Embodiment 2

[0120] With a 30kW variable frequency induction motor, its parameters are shown in Table 2 respectively. Under rated conditions, the voltage and current waveforms of the two motors are as attached image 3 shown. Utilize the solution method of the iron consumption resistance that the present invention proposes, calculated its iron consumption resistance with the change situation of the modulation coefficient of rotating speed and PWM frequency converter as attached Figure 5 . Among them, the switching frequency of the inverter is 5kHz. When the speed is lower than the rated synchronous speed, the ratio of the induced potential to the frequency is guaranteed to remain unchanged; when the synchronous speed exceeds the rated synchronous speed, the induced potential is taken as a constant value. It can be seen that the higher the modulation coefficient of the PWM inverter, the higher the speed of the induction motor, and the greater the equivalent resistance of the iron loss. ...

Embodiment 3

[0122] Using the method of the present invention based on the analytical method and the classic model based on the time-step finite element and the subsection variable coefficient model to calculate the frequency conversion induction motor of a specification such as 5.5kW shown in Table 1 under different supply voltage sinusoidal power supply conditions Iron consumption. The comparison between actual measurement and simulation Figure 6a and Figure 6b shown. It can be seen that the values ​​calculated by the method of the present invention and the segmented variable coefficient model are very close to the measured values.

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Abstract

The invention discloses a calculation method of the iron loss resistance of a variable frequency motor under the condition of PWM harmonics, which belongs to the field of analysis and calculation of the loss of an AC motor. Resistance is expressed as a function of induced potential and rotational speed. This method takes into account the additional iron loss caused by the harmonics of the PWM frequency converter and the surface and pulse loss caused by the space harmonics of the motor. By using the method of the invention, the equivalent circuit of the precise variable frequency motor under the condition of considering the iron loss can be obtained. Finally, taking a 5.5kW and a 30kW variable frequency induction motor as an example, their iron loss resistance variation rules were obtained. And utilize these two induction motors to verify the validity of the present invention.

Description

technical field [0001] The invention belongs to the field of AC motor loss analysis and calculation, and in particular relates to a calculation method for iron loss resistance of a variable frequency motor under the condition of PWM harmonics. Background technique [0002] At this stage, the PWM variable frequency drive system is highly integrated with the induction motor. PWM variable frequency drives contain a large number of harmonic components, which have a great impact on the losses of induction motors. In order to reduce the iron loss of the motor, it should first be able to quickly and accurately calculate the iron loss of the induction motor powered by PWM variable frequency power supply. The iron loss of induction motor can generally be calculated by road calculation (analytic calculation method) or field calculation (finite element method). Due to the consideration of the complex geometry and material properties of the motor, the iron loss calculated based on the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F30/20G01R27/26
CPCG01R27/2694G06F30/367
Inventor 张冬冬武新章
Owner XI AN JIAOTONG UNIV
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