| 摘要 |
PURPOSE:To maintain a quantity of generated heat substantially constant and to miniaturize an apparatus by operating a switching element by reducing a switching frequency when a load to be connected to an inverter is large and increasing the frequency when the load is small. CONSTITUTION:A DC is converted to a VVVF by an inverter 1, and supplied to a load 4 through a CT 2 and a filter 3. An output of the CT 2 is input to an output current operator 6 of a gate controller 5 to be calculated to detect a magnitude of the load and to input it to a switching frequency controller 7. The controller 7 sets a switching frequency to a low value when the load is large and to a high value when the load is small, and controls a gate G of switching elements of the inverter 1 through a gate signal generator 8. Thus, a quantity of generated heat of a circuit is maintained substantially constantly to omit a radiator, and hence an apparatus can be reduced in size. |
