SU659965A1 - Arrangement for checking capacitor tolerances - Google Patents

Description

one

The invention relates to instrumentation engineering and relates to devices for monitoring the tolerances of capacitors.

The capacitor capacitor control devices are known, which contain a generator, an amplifier, a search circuit for tolerance limits, in which the control accuracy is improved by using ac bridges with inductively connected arms {.

The use of such schemes at higher frequencies, in the order of tens and hundreds of kilohertz, leads to an increase in the control error. The main reasons for this are the increase in losses in instrument transformers, the appearance of phase distortions of various nodes (amplifiers, phase-sensitive circuits), and the effect of capacitive leakage between different elements of the circuit. The accuracy of control at these frequencies also depends on the quality of manufacture of transformers and the mode of their operation.

The purpose of the invention is to improve the accuracy of capacitor capacitance control.

The goal is achieved due to the fact that the device for monitoring the tolerances of capacitors, contains, its pavement measuring circuit, the ratio of which

formed by the secondary windings of a voltage transformer, and the other two arms - controlled and exemplary capacitors, and the primary winding of a voltage transformer is connected to a generator, an amplifier connected to the output of a bridge measuring circuit, an indicator, a search circuit for tolerance limits, a corrective transformer,

0 shaper time interval, integrator, key, phaser, actor, relay, switch, and additional amplifier connected via a switch to parallel first connected and reference capacitors and directly to the secondary winding of a voltage transformer. In this case, the outputs of both amplifiers are connected to the input of the time interval generator, the output

0 which is connected to the indicator and to the input of the integrator. The output of the integrator is connected via a switch to the inputs of the search for tolerance limits and the phase shifter, the output of the phase shifter with the primary winding of a correction transformer, the secondary winding of which is connected to the second exemplary capacitor and one output of the branch ratios, and and relay. Ia the drawing shows the scheme of the device. It contains a correction transformer 1, a bridge circuit branch 2, a capacitor 3 arm ranges, an exemplary 4 and controlled 5 capacitors, limiting amplifiers b and 7, a driver 8 times 1x intervals, an ax balance balance 9, an integrator 10, a key 11, controlled phase switch 1, device 12, circuit 13 for search of tolerance limits, capacitor switching relay 14, bridge power generator 15, switch 16. The operation cycle of the proposed device is divided into two main stages: the inclusion of an exemplary capacitor in the bridge circuit, measurement total drift nlech bridge elements and circuit components and devices zanolieiie velichiiy this drift; the inclusion of a controlled capacitor instead of a reference capacitor, the introduction of a correction voltage into the bridge circuit, the amplitude and phase of which are sufficient to compensate for the drift measurement, and the performance of a capacitance control operation. The principle of operation of the device on the first stage, when the model conductor 4 is included in the bridge circuit (autocorrection cycle), is as follows. Due to the drift of the values of the elements of bridge nulls, there is imbalance in it, which is the main source of control error. Its value is measured as follows. The voltage of the measuring diagonal and the reference, which is located on the equilibrium of the bridge in quadrature with the help of the limiting amplifiers 6, 7, are converted into rectangular pulses with fronts corresponding to the moments of the transition of both signals through zero. The imaging unit 8 time slots allocates two adjacent imulses of the same amplitude but of different polarity. The duration of the first pulse is proportional to the phase angle between the voltage of the measuring diagonal and the on-line voltage, and the duration of the second pulse is the phase angle between the inverted voltage of the measuring diagonal and the on-line one. It is not that the total duration of both pulses is equal, and the second pulse is optional for the first one. When the bridge has a capacity capacitance (when the measuring diagonal voltage is in quadrature with the reference) the duration of both pulses is the same, the initial unbalance of the bridge causes a change in the temporal relationship between these pulses, namely, an increase in the duration of one and a corresponding decrease in the duration of the other. The key 11 is open during the autocorrection, the pulses from the output of the imaging unit 8 are fed to the input of the integrator 059 5 10 1.5 20 25 30 35 40 45 50 55 60 65 65 10. The output voltage of the integrator when the volt-second areas of both pulses are equal (i.e. the bridge balance is zero, the imbalance of the bridge leads to the inequality of the areas of these pulses, and a voltage appears at the integrator output, the magnitude and sign of which depends on the magnitude and sign of the initial unbalance. This voltage is fed to the input of a controlled phase driver 1 12 built on a bridge circuit with one adjustable arm, the parameters of which are:) the function of controlling its pairing. With the balance of the control bridge, the voltage at the integrator output is zero and, accordingly, is zero and the output voltage of the phase shifter, the presence of the initial imbalance determines the appearance of this voltage, and its amplitude and phase depend on the magnitude and sign of the unbalance. The output voltage of the phase shifter is inputted into the control bridge in series with the relationship branch using a correction transformer. The bridge is balanced by a change in the amplitude of the phase shifter applied to the branch of the bridge, and the process of working out the entire system ends only when the voltage of the measuring diagonal of the control bridge becomes in quadrature with onor pattern, which is equal to the equal volt-second pulse area forming time. The magnitude of the voltage at the integrator output is proportional to the magnitude of the initial unbalance of the bridge, i.e., in fact, during the autocorrection cycle, this unbalance is measured. At the second stage (control cycle), the controlled capacitor 5 is switched on instead of the reference one via switch 16 controlled by relay 14, and a locking signal is applied to the input of key 11 from the tolerance search circuit at the same time. The key 11 closes, thereby breaking the feedback ring and putting the integrator into memory. The integrator time constant is chosen sufficient to maintain the compensating voltage set in the previous cycle for the entire capacity monitoring cycle. The amplitude of this voltage is equal to the magnitude of the voltage amplitude of the initial unbalance of the controlled bridge, but it is opposite in phase, which leads to the compensation of errors of the shoulder elements. As a result, the error in the control of the capacitance will not depend on the deviations of the values of the bridge elements from the nominal ones, but will be determined only by the inaccuracy of the production of the reference capacitor. Capacity is monitored by switching

the number of transformer dividers of shoulder voltage is equalized by the control bridge with the HOMOLribio donus boundaries search scheme.

Claims (1)

1. T. N. Mantush. Automatic device for mass control of capacitors. “Radio, 1968, 6.