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The analytical program of a voltage source inverter (VSI)-fed permanent magnet synchronous motor (PMSM) with a half-controlled bridge converter and an LC filter is developed. The input voltage of the inverter, that is the capacitor voltage, has a ripple of double frequency of the source due to the phase control of the thyristor. The performance of the motor is significantly influenced by the ripple in the capacitor voltage. This influence can be evaluated by the analytical program.

A generalized analytical model is presented for thyristor- controlled variable inductors. The proposed model can represent the performance of various types of thyristor phase-controlled variable inductors (VI's), e. g., conventional, UM-concept, magnetically coupled reactor, and asymmetrically firing control types, by introducing two parameters: m and ?By means of numerical computation using this model, the characteristics of variable inductors can be clarified, and their characteristics can be compared with ease. This analytical model is very useful for deciding circuit configuration and design.

A circuit controlled by thyristors and having series RLC elements gives rise to a step-up phenomenon. The term step-up is defined with respect to the capacitance voltage on steady state operation, i.e., the ratio of the maximum peak value when controlled by thyristers to the peak amplitude when thyristors are short-circuited exceeds unity. The domain of possible step-up voltage is determined by the angle of displacement between current and voltage and damping factor. The step-up voltages appear across each element, i.e., not only across the capacitance, inductance, and resistance but also across the thyristors. The control characteristic has a distinctive hump phenomenon. The interrupted current results in waveform distortion, phase lag, and improved power factor. The difference of characteristics between the peak and rms values of voltages, particularly of inductance and thyristors, is large. The response time, which is evaluated by numbers of half cycles, is large when the step-up ratio becomes large. The output voltage when the circuit is used as a voltage source has a drooping characteristic.