1524475 Detecting phase angle changes; monitoring motors SCANIAINVENTOR AB 4 June 1976 [6 June 1975] 23223/76 Heading H2K In a circuit for detecting changes in the phase angle between current and voltage on a line 3, 4, 5 a constant-amplitude A.C. signal in phase with the current is derived by oppositely-poled parallel diodes Dl, D2 in the current path, and a similar signal in phase with the voltage is derived by oppositely-poled parallel diodes D3, D4 in a path between two of the line conductors or between one line conductor and a reference (e.g. artificial neutral) point. The current and voltage signals are detected (e.g. by switching amplifiers F1, F2) and supplied to an exclusive- OR gate G, the pulse train output of which has a mark-space ratio dependent on phase. A first, short time constant, smoothing circuit R8, C1, R9, C2 derives a D.C. voltage a representing the phase and able to follow changes thereof quickly, whilst a further, long time constant, smoothing circuit R10, C3 derives a voltage b which follows changes in phase more slowly. Amplifier F3 compares the voltages a, b from the two smoothing circuits and provides a first output level when ab and a second level when ab, each transition from one level to another thus corresponding to a change in phase. The circuit may be used to detect whether several changes of phase occur in rapid succession, e.g. due to a fan 1 going in and out of stall repetivively. Each transistion from the first to second level adds an increment of charge to a capacitor, and if a number of such transitions occur close together the capacitor voltage will exceed a reference (P), thus switching on a transistor TR to operate a protective relay RL and l.e.d. LD.
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机译:1524475检测相角变化;监视电机SCANIAINVENTOR AB 1976年6月4日[1975年6月6日] 23223/76标题H2K在用于检测3、4、5线路上电流和电压之间的相角变化的电路中,一个与电流同相的恒定振幅AC信号在电流路径中由反向极化的并联二极管D1,D2得出,在两个线路导体之间或一个线路导体之间的路径中,由反向极化的并联二极管D3,D4得出与电压同相的相似信号。以及参考点(例如人为中立点)。检测电流和电压信号(例如,通过开关放大器F1,F2),并将其提供给异或门G,该异或门G的脉冲串输出具有取决于相位的标记空间比。第一,短时间常数的平滑电路R8,C1,R9,C2得出一个表示相位并且能够快速跟随其变化的直流电压a,而另一个长时常数的平滑电路R10,C3得出一个电压b。跟随相位变化的速度较慢。放大器F3比较来自两个平滑电路的电压a,b,并且当a <b时提供第一输出电平,而当a> b时提供第二输出电平,每个输出电平从一个电平转换到另一个电平,因此对应于相位变化。该电路可以用于检测是否快速连续地发生了几个相位变化,例如,相位变化。由于风扇1连续进出失速。从第一级到第二级的每个晶体管向电容器增加电荷的增量,并且如果大量这样的跃迁发生在一起,电容器电压将超过参考电压(P),从而接通晶体管TR来操作保护继电器RL并带领LD。
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