| 摘要 |
1294605 Measuring mean voltage LICENTIA PATENT-VERWALTUNGS GmbH 20 May 1970 [22 May 1969] 24327/70 Heading G1U In order to produce a D.C. potential with respect to neutral, MPL, proportional to the halfwave mean potential U3 across a load 3 connected to neutral via thyristors 1, 2, controlled so that each conducts for the same fraction of a half cycle, the load is shunted by a rectifying potential divider, 4, 5, 9, 8, the middle point of which is connected to an RC circuit 6, 7, having a large time constant relative to the main supply P frequency, and a low D.C. resistance relative to the potential divider resistors 5, 9, which are equal to each other. In operation during positive half cycles of the supply P the mean current through resistor 6 is proportional to the half-cycle mean of the supply voltage, irrespective of whether thyristor 2 conducts or not. During negative half cycles of the supply, for those periods that thyristor 1 is not conducting the mean current through resistor 6 is proportional to the mean voltage U2 across the thyristor (which voltage will equal the supply voltage), and for those periods that thyristor 1 is conducting the mean current through resistor 6 is zero. Thus, in positive half cycles of the supply the potential across resistor 6 and capacitor 7 rises towards the mean supply voltage, whilst for those fractions of negative half cycles of the supply during which no load current flows, the potential across resistor 6 falls towards the negative mean supply voltage, so that the net voltage across resistor 6 represents the half-wave mean of the voltage applied to the load 3. |
