SU1308937A1 - Device for measuring the winding resistance of a.c.electric equipment - Google Patents

Abstract

The invention relates to a measurement technique and can be used in the automatic control and measurement of the DC resistance of the windings of an AC electrical equipment. The aim of the invention is to increase the accuracy of measurement by eliminating errors caused by the presence of variable components in the measuring diagonals of the bridges, and speed. The device contains a constant-current source 2, a current measuring transducer 8, a recording unit 19. To achieve this goal, a current transformer 7, a voltage divider I, a voltage transformer 4, a voltage measuring converter 5, an additional resistor 3, are inserted into the device measuring channels, dividing unit 17, integrator zero-setting unit 20, period allocating unit 24, new functional connections are formed. 2 Il. w (L with about 00 with so

Description

The invention relates to a measurement technique and can be used in the automatic monitoring and measurement of DC resistance of the windings of AC electrical equipment, including electric machines under load, fed by a periodic non-sinusoidal voltage.

The aim of the invention is to improve measurement accuracy by eliminating errors due to the presence of variable component bridges in the measurement diagonals and speed.

Figure 1 presents the block diagram of the device; Fig. 2 illustrates stress plots at various points of the device.

The device consists of a parallel voltage divider 1, a constant voltage source 2 with an additional resistor 3, a voltage transformer 4, a voltage measuring converter 5 and the winding 6 under study with a current transformer 7 and a current measuring converter 8, two adders 9 and 10 the first of which connects the outputs of the transformer 4 of the voltage and the measuring converter 5 of the voltage to the input of the first integrator via the signal input of the first switch 11 of the measuring channel and the first block 12 of matching ator 13, and the second through the signal input of the second switch V4 of the measuring channel and the second matching unit 15 connects the outputs of the current transformer 7 and the current measuring converter 8 to the input of the second integrator 16, dividing unit 17 connected to the outputs of the first and second integrators 13 and 16, the third matching unit 18 and the registering unit 19, the integrator zero setting unit 20, comprising the first key management unit 21 and the zero setting keys 22 to 23, the period extracting unit 24 connected between the output of the voltage divider 1 and controlling the inputs of keys 11 and 14 of the measuring channel and containing a low-pass filter 25 connected in series, limiter 26, first differentiator 27, first diode 28, block 29 of coincidence (via input X,), trigger driver 30 (via T -input and 0-output) and the second block 31 control 10

15

20

25

thirty

35

40

45

50

55

neither keys, as well as serially connected start block 32, one-shot 33, second differentiator 34, second diode 35, inverter 36, and control trigger 37 (via S-in and Q-out), while the output of one-oscillator ЗЗ is connected to the input the first key management unit 21, the output of the second differentiator 34 is connected to the R input of the trigger generator 30 and the R input of the control trigger 37 via the third diode 38, the Q output of the control trigger 37 is connected to the input X of the matching unit 29, and the T input control trigger 37 is associated with the Q output of trigger trigger 30 via rety differentiator 39 and fourth diode 40.

Measuring transformer 7 and measuring transducer V current included from the zero point of the investigated winding 6.

The integrators 13 and 16 can be performed, for example, on the basis of an operational amplifier, where the blocks 12, 15 and 18 of the matching are scaling amplifiers, and the division block 17 is a divider of analog signals.

The device works as follows.

A voltage divider 1, a primary winding of a voltage transformer 4, a voltage measuring converter 5 and a winding 6 under study are applied voltage proportional to the supply voltage and the voltage of the constant voltage source 2 (Fig. 2a).

In the adder 9, the variable components present in the secondary voltage of the voltage transformer 4 are subtracted from the output voltage of the transmitter 5. The signal inversion is provided by appropriately connecting the secondary winding of the voltage transformer 4 to the adder 9. A differential signal is applied to the signal input of the switch 11 of the measuring channel.

At the same time, in the adder 10, the voltage proportional to the variable component of the current is subtracted from the voltage proportional to the current of the winding 6 under study. The differential signal is applied to the signal input of the key 14 of the measuring channel.

Matching blocks 12, 15, and 18 change the signal values when integrating analog signals. When digitally integrated, blocks 12 and 15 of matching converts analog signals to digital codes, and block 18 of matching performs a digital-to-analog conversion.

The integrator zero setting unit 20 eliminates the presence of voltage on the integrators 13 and 16 at the time the integrated signals are fed to them. The integrators 13 and 16 isolate the constant components of the voltage of the test winding and a voltage proportional to the current of the test winding. The integration takes place on a time interval equal to the period of the first harmonic of the supply voltage, during which the keys AND and 14 of the measuring channel are closed by means of a control signal from the period extracting unit 24.

The signal proportional to the resistance of the direct current of the investigated winding is removed from the output of dividing unit 17 and recorded by the detecting unit 19.

To form the output signal of the period separator 24 from the voltage removed from the voltage divider 1 (Fig. 2a), the first harmonic is selected with the help of the low-pass filter 25 (Fig. 22). Next, the limiting amplifier 26 forms a square-shaped voltage with a period equal to the first harmonic period (Fig. 26 This voltage is differentiated by the first differentiator 27 (Fig. 2d), and the first diode 28 transmits positive pulses to the input X, block 29 duration, following the frequency of the first harmonic voltage supply (Fig.2a).

At the time of the beginning of the counting (time t), the pulse from the start-up unit 32 is fed to the one-shot 33. The output positive signal of a small one-shot time (Figure 2e) is applied to the input of the first key control unit 21, which closes the key 22 and 23 of the zero setting . Through the closed keys 22 and 23 of the zero setting, the capacitors of the integrators 13 and 16 are discharged, and zero initial voltages are set at the integrators. At the end of the signal with

the one-shot 33, the keys 22 and 23 of the zero setting are opened.

The signal of the one-shot 33 simultaneously enters the input of the second differentiator 34, from the output of which the positive and negative pulses corresponding to the leading and trailing edges of the one-shot 33 are removed (Fig. 2g). A positive output pulse of the second differentiator 34 (Figures 2-1-) through the third diode 38 is supplied to the R-inputs of the control trigger 37 and the trigger generator 30, transferring each of them to the O position, or confirming the already existing O position of Fig.2 ( d, solid and dashed lines in the interval 0-t characterize possible values of the voltages of the flip-flops by the time of reference).

The negative output pulse of the second differentiator 34 passes through the second diode 35, changes the field in inverter 36 (Fig. 2k) and is fed to the S input of control trigger 37, translating it to position 1 (Fig. 2). From the Q output of the trigger 37, control, a positive resistor voltage is applied to the input Xj of the matching unit 29. The coincidence unit 29 transmits a positive pulse from the first diode 28 to the T input of the trigger generator 30 (FIG. 2L). The trigger driver 30 moves to position 1. A positive voltage is applied to the input of the second key management unit 31. The keys 11 and 14 of the measuring channel are closed and provide the input of measured signals to the integrators 13 and 16. The subsequent positive im-; The pulse from the first diode 28 passes through a block 29 of coincidence and returns the trigger driver 30 to the position O (Fig. 2m). The second key management unit 31 receives a zero voltage. Keys 11 and 14 of the measuring channel, which will be closed

during the period, open. I

From the Q output of the trigger driver 30 (FIG. 2n), the signal arrives at the third differentiator 39, from the output of which the alternating polarity pulses arrive at the diode 40. A positive pulse corresponding to a positive voltage period at the Q output of the trigger driver 30 (FIG. .2o), passes through the diode 40 to the T-input

control trigger 37 (Fig. 2o) and returns trigger generator 30 to position O. Prohibitory voltage is applied to input X of coincidence unit 29 from control trigger 37. The coincidence unit 29 does not transmit subsequent positive pulses from diode 28.. ,

For integrators on operational amplifiers, the output voltage of the first integrator, after time T

and MyTi, where K is a constant integration

the first integrator; T is the period of the first harmonic of the supply voltage;

and

Ou

constant input voltage component of the first integrator. Output voltage of the second integrator after time T

and K; and .. T, where K is a constant integration

second integrator; and - a constant component of the input voltage of the second integrator.

In dividing block 17, a voltage proportional to the resistance of the direct current is calculated.

The integration constant Kc (Kp is determined by calibration at a constant voltage, based on the ratio

K, and „/ (it,),

where and is the constant voltage applied to the integrator input;

Uj is the voltage at the integrator output;

T, is the integration time. With digital integrators, the symbols and, Uy and U- characterize the voltage values numerically.

Claims (1)

Invention Formula A device for measuring the resistance of the windings of electrical equipment of an alternating current, containing a source of direct voltage, a measuring current transducer and a recording unit, characterized in that, in order to improve measurement accuracy and speed, a voltage divider , voltage transformer, voltage measuring transducer, additional rheistor, two identical measuring channels, division unit, integrator zero setting unit and period separating unit, and The primary winding of the current transformer is connected in series with the test winding and the input of the current converter, voltage divider, voltage transformer, the primary winding of the voltage converter and the constant voltage source with an additional resistor are connected in parallel to the branch, each The measuring channel consists of a series-connected adder, a key of the measuring channel, a matching unit and an integrator, the inputs of the first adder are connected to the secondary winding of the voltage transformer and the output of the voltage converter, the inputs of the second adder are respectively connected to the secondary winding of the current transformer and the output of the current converter , the integrator outputs are connected to the inputs of the division unit, the output of which is connected to the recording unit through the third matching unit block, the integrator zero setting block contains the first key control block connected to the second input of each integrator via its zero key, and the period selection block is connected between the output of the voltage divider and the control inputs of the keys of the measuring channel and consists of a series-connected low-pass filter, the amplifier limiter, the first differentiator, the first diode, the coincidence unit, the trigger generator, and the second key management unit, as well as from the series-connected the start block, the one-shot, the second differentiator, the second diode, the inverter, the output of which is connected to the S input of the control trigger, the one-shot output connected to the input of the first key control unit, the output of the second differentiator connected to the R-input of the trigger forming and the R input of the trigger control through the third diode, the Q output of the control trigger is connected to the second input of the matching unit, and the T input of the control trigger is connected to the Q output of the trigger driver via the third differentiator and the fourth diode.