INVERTER APPARATUS FOR FORKLIFT

摘要

PROBLEM TO BE SOLVED: To provide an inverter apparatus by which the loss of an inverter is reduced and by which a temperature rise is reduced by a method in which a plurality of FETs are connected in parallel and a composite switching element which is connected in parallel with a IGBT is used. SOLUTION: An inverter apparatus is composed of a means by which a semiconductor switch is connected in parallel with an insulated-gate bipolar transistor and with a plurality of field-effect transistors and by which a coil 8-1 at an AC motor 7 is star-connected by a normally closed contact at a three- phase changeover contactor 13 and of a means by which coils at the AC motor 7 are delta-connected by a normally open contact at the three-phase changeover contactor 13. The frequency of a switching element 5 connected to the (+) side is lowered to several fractions of the frequency of a switching element 5 connected to the (-) side.