| 摘要 |
PURPOSE:To apply a DC braking without damage to an induction motor with a simple circuitry by stopping a basic clock of an inverter when a DC voltage lowers down to the level the same as the braking voltage applied to a converter at braking. CONSTITUTION:When an input ''1'' is applied to a control terminal C as braking command, the output of a comparator 19 is ''0'' while DC power supply voltage VP is higher than voltage braking voltage VB. A voltage adjustor 3 sends the voltage VB and the torque of an induction motor 10 with a gradual drop of the voltage VP. When VP=VB, the output of a comparator 19 goes to ''1'' while the output of an AND gate 11 to ''1''. Consequently, the input of a ramp wave generator 13 moves to ''0'' and the application of the oscillation frequency to a ring counter 17 is stopped. Therefore, an inverter 2 is stopped at any one of six driving modes and a DC voltage is applied to a stator winding of the induction motor 10 as an exciting voltage at a lower level that the DC power supply voltage at the normal time. |
