| 摘要 |
PROBLEM TO BE SOLVED: To surely suppress overcurrent in an inverter device. SOLUTION: A V/f-controlled inverter device is constituted to perform PWM control on an inverter 4 by computing a PWM voltage pattern from a q-axis voltage command Vd* set at 0 V, by using a frequency command fs * and the q-axis voltage command Vd* converted from the frequency command fs * by means of a V/f converter 2. When the inverter device performs the PWM control, the device calculates the difference between a primary current vector I1 from a current detector 6 which detects the primary current of a motor 5 and an overcurrent limiting value I1- max by means of a subtractor 71, extracts the positive signal of the difference by means of a limiter 74, and obtains the absolute value DV of a compensating voltage by multiplying the extracted signal by a gain Koc by means of an overcurrent compensating voltage generating gain 78. Then the inverter device obtains d- and q-axis voltage compensating values DVd and DVq, by respectively multiplying the absolute value DV by detected d- and q-axis current values Id and Iq by means of multipliers 81 and 82, and suppresses the overcurrent by adding the compensating values DVd an DVq to the commands Vd* and Vq* in inverse vector through subtractors 21 and 22 and, at the same time, by reducing the Vq* from the converter 2 by performing PI computation on the above-mentioned DV by means of a PI controller 10 and feeding back the computed DV to the frequency command fs * as a frequency feeding-back value. |
