SU123616A1 - Method for measuring electric power consumed by receiver - Google Patents

Description

In many practical cases, it is desirable to obtain an output at the output of the device proportional to the measured power. This is especially important, for example, when it is necessary to add power over the indications of several instruments in telemechanical measurement systems.

At present, this problem is solved by means of devices with squareing and summing static elements, which, despite their complexity, do not provide the necessary accuracy due to the instability of the characteristics included in the scheme of these devices of linear and nonlinear elements.

The proposed method of power measurement is devoid of this drawback, since it is based on the use of phase-sensitive rectifying circuits only.

Power measurement is carried out using two such circuits, one of which is used to obtain a voltage proportional to the active component of the current consumed by the receiver, and the second is the time to multiply the value obtained by a voltage proportional to the measured voltage by the time-pulse method . The second phase-sensitive rectifier circuit is controlled by the difference of the rectified auxiliary voltage of a constant, amplitude and constant voltage proportional to the measured one.

The drawing is a schematic diagram of a device for implementing the proposed method.

Resistance i is derived from a voltage proportional to the load. This voltage is rectified by a phase-sensitive rectifier circuit of a low-frequency switch, switched voltage, removed from section 123616-2 -

the main winding of the transformer T, powered from the network. The rectified voltage at the output terminals of the phase-matching rectifying circuit of the FWH (between points 1 and 2), proportional to the product / cos to (/ - load current, o - phase angle between load current and network voltage), is averaged by capacitor Cj and is fed to the input (points 3 - 4) of the phase-sensitive computational circuit of the FWH.

From the secondary winding of the transformer T, an alternating voltage proportional to the network voltage V is removed, rectified by the valve BI and averaged by the capacitor Cg. As a result, a constant voltage appears between the 5 m 6 points, proportional to the voltage of the network V. Part of it falls on the resistance (resistance is used to eliminate the effect of the capacitor Cz on the shape of the sawtooth pulses).

Thus, a constant voltage proportional to / cose is applied to the points of a 3-4 phase-sensitive FPW circuit; a constant voltage proportional to V is applied to points 5 to 7 of the same circuit. To the points 8 and 9 of the phase-sensitive FP circuit, Saw voltage with amplitude E from generator G PI so that it lowers valves 3 and B (for example, proportional to I VL V are unlocking voltages).

It is obvious that the current through the valves 2 and B will pass only for the duration of the time during which the instantaneous value of the sawtooth voltage is less than the algebraic sum — and V (taking

it is conditional that the voltages proportional to -y and V are equal- and V).

When the resistances R and R are equal, the voltage is divided equally between the two parts of the phase-sensitive rectifier frequency converter circuit, divided by the switching circuit.

Since voltage V is applied to both valves with the same

/ sign, and voltage - with different signs, then, of course, that

The currents through the resistances RQ and R have different values (it is assumed that R & and much more than the other resistances, input w; they are in the circuit).

Under these conditions, the voltage across the resistances RQ and Rj are:

on the resistance of Re: (E - V-)

on resistance Rj: (Е - V + -).

The difference in voltage drops across the resistances R and Ri is equal to the voltage between points 10 and 11. It is easy to show that this voltage has the form of trapezoidal pulses.

The average value of R p for this voltage is proportional to the partial value of U t. where 5 is pollo, ats the indicated pulses and G is the period of sawtooth pulses.

From here you can derive:

S iv cos

&., „V,

where k is the proportionality coefficient.

Thus, at a constant value of the amplitude of the sawtooth voltage Ea, the measuring device I DC shows the power consumed in the AC circuit.