| Title |
A Study on the PWM Strategy and Gear Changing Techniques of an Inverter for Variable Speed Drives on Traction Motors |
| Authors |
서영민(Seo, Yeong-Min) ; 박영진(Park, Yeong-Jin) ; 홍순찬(Hong, Sun-Chan) |
| Keywords |
Pattern Changing ; PWM Inverter ; SPWM ; SHE PWM |
| Abstract |
This paper deals with PWM patterns for harmonic reduction in inverter fed traction motors and the gear changing techniques for the variable speed drive of traction motor. GTOs are used as switching device of inverter because traction motor is a large load. To derive PWM rattern which can minimize the harmonics with the limited switching frequency, the output current and torque characteristic of SPWM and SHE PWM was analyzed. GTO inverter used for traction motor drive includes harmonics in the output current and torque by the limitation of switching frequency. However, the hybrid PWM method that adopt SPWM in the range of low frequency and SHE PWM in upper frequency range can achieve less harmonic characteristics in GTO inverters. If the traction motor is driven in variable speed by the proposed PWM pattern, 7 times of gear changing is needed. At the instant of the mode change, magnetic flux and torque may be altered and the large current flow. To reduce such an undesirable transient behavior, it is also presented the technique for the gear changing of inverter fed traction motor drive operated with the hybrid PWM. The results are verified by simulations and experiments. |