METHOD FOR OVERVOLTAGE PROTECTION OF HIGH-VOLTAGE ADJUSTABLE RECTIFIERS Russian patent published in 2008 - IPC H02H7/12 

FIELD: electrical engineering.

SUBSTANCE: phase α of control pulse front edge is measured continuously by a thyristor switch of converter unit as well as phase ϕ of load current pulse edge, which is defined by automatic adjustment system, and their difference is calculated. Normal operating mode is that when the difference α - ϕ is less or equal to the maximum allowed value of the load current delay angle. Open circuit mode is that when the difference α - ϕ is greater than the maximum allowed value. In this case a signal is generated to reduce control angle of the thyristor switch or to switch off the automatic switch in the converter supply circuit. Another distinction of the suggested method of overvoltage protection is that current amplitude of voltage on the electric filter, Uf, and corresponding amplitude of load current pulse, If, are measured continuously in each half-cycle. Normal operating mode is that when at predefined level of overvoltage, Ua, amplitude of load current pulse, Ia, is greater than zero. At that, amplitude of voltage on the electric filter is limited at the level of maximum allowed value for given type of converter unit. Open circuit mode is that when at predefined level of overvoltage, Ua, amplitude of load current pulse, Ia, is equal to zero. In this case a signal is generated to change the level of overvoltage limit on the electric filter down to the Ua value, which is considerably lower than the allowed value, for example, about thirty or forty percent of maximum amplitude of converter overvoltage, or a signal is generated to switch off the automatic switch in the converter supply circuit.

EFFECT: improvement of reliability.

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