| 摘要 |
915,361. Rectifying. BROOKHIRST IGRANIC Ltd. April 1, 1959 [April 3, 1958], No. 11032/59. Class 38 (2). A polyphase full-wave rectifier network includes pairs of controlled rectifiers conductive at the same time in each phase and a timeconstant circuit associated with the rectifiers in each phase, the time-constant circuit having different charging and discharging time constants, and being arranged so as to prevent conduction through a rectifier in another phase during conduction in its own phase. Rectifiers T1, T2, T3 are controlled by controller C to conduct in sequence and when one of these rectifiers, say T1, conducts the voltage drop across the associated resistor R4 charges condenser C1 so as to apply a negative bias to the grid of rectifier T4<SP>1</SP> to prevent conduction thereof due to back E.M.F. from an inductive load. Condenser C1 discharges slowly through resistor R2. When T4<SP>1</SP> is required to conduct in its correct sequence, its grid is positively biased through potential divider R1, R2. In a modification, Fig. 2, transformers PT1, PT2, PT3 are provided so that an additional positive bias is applied to the grid of that rectifier which is required to conduct. The primary winding of each transformer is connected across a resistor R4. When T1 conducts, T4<SP>1</SP> is biased to cut-off by C1 as before, but the grid of T6<SP>1</SP> receives an additional positive bias through PT1. Specification 876,888 is referred to.
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