1987 Ryhmebus was established. Marketing of RM2 series (AC PWM inverter). 1988 Completed developing RM2 inverters for 1 HP~30 HP and selling on the market. 1989 Installed a developing program for RM4 series(40 HP~150 HP) and auxiliary control equipment. 1990 Explored international trade, started with Korean market. 1991 RM3 (1HP~30HP) keypad programmable inverters were developed. 1992 Technical transfer of AC spindle driver from Mechanical Industry Research Laboratories, ITRT(Industrial technology research Institute). 1993 Close-loop controller in high speed induction motor and synchronous mot
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