| 摘要 |
PURPOSE: To obtain a measuring method in which a primary resistance value can be measured simply by measuring the output current of a three-phase inverter measuring and computing the primary resistance value of an induction motor on the basis of a specific expression. CONSTITUTION: A voltage control factor K and a phase θ0 in a PWM pattern are decided. At this time, the control factor K is decided by taking a voltage drop at a switching element into consideration so that a designated voltage can be applied to the terminal of an induction motor. Then, a voltage based on the PWM pattern is applied to the induction motor, it is detected that a current value has become constant (the change rate ΔI1 /Δt of a current is within a prescribed value) and a primary current value I1 is found by I1 =1/√3.√(Iu <2> +Iv <2> +Iw <2> ) (where Iu , Iv and Iw represent currents at a U-phase, a V-shape and a W-phase, respectively). Then, the application of the voltage based on the pattern is cut off, and a primary resistance value R1 is computed on the basis of R1 =KVd /2√2.I1 ) (where Vd represents the output voltage of a rectifier). This operation is executed five times, the mean value which has excluded a maximum value and a minimum value is computed on the basis of a sample value, and the resistance value R1 is computed. |
