PURPOSE: To drive a main switching element while matching with a real PWM pulse pattern by subjecting the ON pulse width of the switching element to subtraction correction by an amount corresponding to turn OFF time of the switching element.
CONSTITUTION: A converter 2 connected with an AC three-phase power supply 1 and an inverter 3 connected with the output of the converter 2 are provided, and an induction motor 4 is subjected to driving control based on the output from the inverter 3. A converter controller 13 and an inverter controller 14 control the converter 2 and the inverter 3 respectively. Other switching elements can not be turned ON before actual turn OFF after turn OFF of the gate pulse of one switching element. Consequently, ON pulse width of the switching element is subjected to subtraction compensation by an amount corresponding to the turn OFF interval. By such arrangement, a real PWM pulse width can be realized.
INABA HIROMI
ANDO TAKEYOSHI
KONYA MASAHIRO
OUCHI NAOYUKI
HITACHI BUILDING SYST ENG
HITACHI ENG CO LTD
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