| 摘要 |
PURPOSE:To prevent the failure of commutation when a power supply voltage is lowered by a commutation angle controller by picking up a phase leading voltage from the differential voltage between the phase of the current and the phase of the current to be commutated next, comparing the phase leading voltage with predetermined level voltage of a setting unit and thus limiting the commutation leading angle. CONSTITUTION:A beta limiting level detector circuit in a phase shifter 13 for controlling the phase of the thyristor bridge 6 of an external commutated inverter leads a voltage a' through a circuit having resistors 32, 33 and a capacitor 31 to a voltage having leading phase and applies it to a level detector 25 together with positive voltage from a control resistor 34. A detector 25 detects zero point, and supplies to an OR gate 26 to limit the commutation leading angle by an AND gate 27. Even if the power voltage is therefore varied, this controller can control the commutation angle so that the commutation voltage product may substantially become constant. Accordingly, it can prevent the failure of the commutation and utilize the inverter voltage to its maximum level. |
