| 摘要 |
PROBLEM TO BE SOLVED: To set a starting voltage as an optimum value by adding a voltage drop to an initial voltage, outputting a voltage set at starting time, automatically setting a voltage value set for the starting time, and starting it. SOLUTION: A V-F converter 6 calculates a starting voltage Vs according to V-F characteristics of a motor for an arbitrarily set starting frequency fs by using a motor rated frequency fr and motor rated voltage Vr. Then, a starting time voltage setter 12 calculates a voltage drop component dV of the motor, adds the voltage drop component Dv to the set voltage Vs, and sets a starting time set voltage Vs'. A current-voltage converter 27 converts PI current ΔI from a limiter 26 into a voltage ΔV by using the starting time voltage set value Vauto and rated current Is, and outputs it to a PWM calculator 7 via a changeover switch SW1 . Accordingly, a motor 4 starts by a PWM-controlled inverter 1 at the frequency fs and voltage ΔV. |
