CN219737744U - A calibration device for transformer DC resistance tester - Google Patents

Abstract

The utility model provides a calibration device of a transformer direct current resistance tester, which comprises a main control chip, wherein the main control chip generates a first PWM signal, a second PWM signal and a third PWM signal for respectively controlling output values of a first voltage lifting circuit, a second voltage lifting circuit and a third voltage lifting circuit; the three voltage acquisition modules convert the output currents of the A phase, the B phase and the C phase of the transformer direct current resistance tester into voltage signals U _a 、U _b And U _c Voltage signal U _a 、U _b And U _c One path is respectively sent to the main control chip, and the other path is respectively used as the control voltage input of the three voltage lifting circuits. The device not only can realize transformationThe device has three current sampling circuits, so that the requirement of calibration of the three-loop transformer direct current resistance tester can be completely met, and the working efficiency is greatly improved.

Description

A calibration device for transformer DC resistance tester

Technical field

The utility model relates to the technical field of tester calibration devices, in particular to a transformer DC resistance tester calibration device.

Background technique

Transformer DC resistance tester is an instrument used to test the DC resistance between the windings of single-phase and three-phase transformers. Common transformer DC resistance testers on the market include single-circuit (used for testing DC resistance of single-phase transformers) and three-circuit Two types (for testing DC resistance of three-phase transformers).

Currently, the resistance value traceability method of transformer DC resistance testers adopts the physical standard resistance method. Since the physical standard resistances are all fixed resistance values, this results in that the transformer DC resistance tester can only be calibrated with fixed resistance value points, while the The resistance value between fixed resistance values cannot be calibrated, and the purpose of continuously adjustable calibration of the resistance value of the transformer DC resistance value tester cannot be achieved. At the same time, this method of using physical standard resistors is only suitable for calibrating single-circuit transformer DC resistance testers. For three-circuit transformer DC resistance testers, it is necessary to calibrate the DC resistance value of each phase according to A phase, B phase, and C phase. Traceability is required, and rewiring is required every time the phase is commutated. The operation is complex and troublesome, the degree of automation is low, and the overall work efficiency is extremely low.

Utility model content

The technical problem to be solved by this utility model is to provide a calibration device for a transformer DC resistance tester, which can facilitate the calibration of a three-circuit transformer DC resistance tester.

The utility model is implemented as follows: The utility model provides a transformer DC resistance tester calibration device, which includes a main control chip and a first voltage acquisition module, a second voltage acquisition module, and a third voltage acquisition module respectively connected to the main control chip. a voltage acquisition module, a first voltage rise and fall circuit, a second voltage rise and fall circuit and a third voltage rise and fall circuit;

The main control chip generates a first PWM signal, a second PWM signal and a third PWM signal. The first PWM signal, the second PWM signal and the third PWM signal respectively control the first voltage rise and fall circuit and the second voltage rise and fall circuit. and the output value of the third voltage boost circuit;

The first voltage acquisition module converts the output current I _A of phase A of the transformer DC resistance tester into a voltage signal U _a , and the second voltage acquisition module converts the output current I _B of phase B of the transformer DC resistance tester into voltage Signal U _b , the third voltage acquisition module converts the output current I _C of the C phase of the transformer DC resistance tester into a voltage signal U _c . The voltage signals U _a , U _b and U _c are divided into two channels. One way of the voltage signals U _a , U _b and U _c is sent to the main control chip respectively, and the other way is used as the control voltage input of the first voltage rise and fall circuit, the second voltage rise and fall circuit and the third voltage rise and fall circuit respectively.

Further, the first voltage acquisition module includes a first standard load resistor and a first current sampling circuit. The first standard load resistor is connected to the first current sampling circuit. The first current sampling circuit is connected to the main control chip. connect.

Further, the second voltage acquisition module includes a second standard load resistor and a second current sampling circuit. The second standard load resistor is connected to the second current sampling circuit. The second current sampling circuit is connected to the main control chip. connect.

Further, the third voltage acquisition module includes a third standard load resistor and a third current sampling circuit. The third standard load resistor is connected to the third current sampling circuit. The third current sampling circuit is connected to the main control chip. connect.

Further, the accuracy level of the first standard load resistance, the second standard load resistance and the third standard load resistance is higher than or equal to 0.01 level.

Further, the first voltage rise and fall circuit is used to output the voltage signal U _A. The first voltage rise and fall circuit includes an inductor L1, a diode D1, a full control device Q1, a capacitor C1 and a resistor R1;

The base of the full control device Q1 is connected to the first PWM signal, the collector of the full control device Q1 is connected to the voltage signal U _a , and the emitter of the full control device Q1 is connected to the cathode of the inductor L1 and the diode D1 respectively. , one end of the capacitor C1 and the resistor R1 is connected to the anode of the diode D1 respectively, and the other end of the capacitor C1 and the resistor R1 is connected to the inductor L1 respectively.

Further, the second voltage rise and fall circuit is used to output the voltage signal U _B. The second voltage rise and fall circuit includes an inductor L2, a diode D2, a full control device Q2, a capacitor C2 and a resistor R2;

The base of the full control device Q2 is connected to the second PWM signal, the collector of the full control device Q2 is connected to the voltage signal U _b , and the emitter of the full control device Q2 is connected to the cathode of the inductor L2 and the diode D2 respectively. , one end of the capacitor C2 and the resistor R2 is respectively connected to the anode of the diode D2, and the other end of the capacitor C2 and the resistor R2 is connected to the inductor L2 respectively.

Further, the third voltage rise and fall circuit is used to output the voltage signal U _C. The third voltage rise and fall circuit includes an inductor L3, a diode D3, a full control device Q3, a capacitor C3 and a resistor R3;

The base of the full control device Q3 is connected to the third PWM signal, the collector of the full control device Q3 is connected to the voltage signal U _b , and the emitter of the full control device Q3 is connected to the cathode of the inductor L3 and the diode D3 respectively. , one end of the capacitor C3 and the resistor R3 is respectively connected to the anode of the diode D3, and the other end of the capacitor C3 and the resistor R3 is connected to the inductor L3 respectively.

The advantage of this utility model is that: the device obtains the voltage loaded on three standard load resistors through three voltage acquisition modules. On the other hand, the main control chip uses the sampled current value and the resistance that is pre-written in the main control chip to be calibrated. Multiply the values to calculate the voltage value, and compare this voltage value with the voltage collected by the main control chip through the current sampling circuit to obtain a proportional coefficient value. The main control chip generates a PWM signal based on this proportional coefficient value to control the rise and fall of the three voltages. The output of the circuit is sent to the voltage input end of the transformer DC resistance tester to achieve calibration of the transformer DC resistance.

The three-way voltage rise and fall circuit designed in this device can control the values of voltages U _A , U _B and U _C to adjust up and down the values of U _a , U _b and U _c instead of boosting or reducing the voltage simultaneously, which is more convenient and flexible.

This device can not only achieve continuously adjustable calibration of the DC resistance value of the transformer, but also has three current sampling circuits that can fully meet the calibration requirements of the three-circuit transformer DC resistance tester, greatly improving work efficiency.

Description of the drawings

The utility model will be further described below with reference to the accompanying drawings and embodiments.

Figure 1 is a schematic structural diagram of the utility model;

Figure 2 is a schematic structural diagram of the first voltage boosting circuit of the present invention;

Figure 3 is a schematic structural diagram of the second voltage boosting circuit of the present invention;

Figure 4 is a schematic structural diagram of the third voltage boosting circuit of the present invention;

Figure 5 is a schematic diagram of the waveforms of U _A , U _B and U _C when boosting according to the present invention;

Figure 6 is a schematic diagram of the waveforms of U _A , U _B and U _C during voltage reduction according to the present invention.

Detailed ways

Please refer to Figures 1 to 6. The present utility model provides a calibration device for a transformer DC resistance tester, which includes a main control chip and a first voltage acquisition module, a second voltage acquisition module, and a third voltage acquisition module respectively connected to the main control chip. A voltage acquisition module, a first PWM signal, a first voltage rise and fall circuit, a second PWM signal, a second voltage rise and fall circuit, a third PWM signal and a third voltage rise and fall circuit;

The main control chip generates a first PWM signal, a second PWM signal and a third PWM signal. The first PWM signal, the second PWM signal and the third PWM signal respectively control the first voltage rise and fall circuit and the second voltage rise and fall circuit. and the output value of the third voltage boost circuit;

The first voltage acquisition module converts the output current of phase A of the transformer DC resistance tester into a voltage signal U _a , and the second voltage acquisition module converts the output current of phase B of the transformer DC resistance tester into a voltage signal U _b , The third voltage acquisition module converts the output current of phase C of the transformer DC resistance tester into a voltage signal U _c . The voltage signals U _a , U _b and U _c are divided into two channels. The voltage signals U _a , U One channel _b and U _c are respectively sent to the main control chip, and the other channel is used as the control voltage input of the first voltage rise and fall circuit, the second voltage rise and fall circuit, and the third voltage rise and fall circuit respectively.

Specifically, the first voltage acquisition module includes a first standard load resistor and a first current sampling circuit. The first standard load resistor is connected to the first current sampling circuit. The first current sampling circuit is connected to the main control chip. connect.

Specifically, the second voltage acquisition module includes a second standard load resistor and a second current sampling circuit. The second standard load resistor is connected to the second current sampling circuit. The second current sampling circuit is connected to the main control chip. connect.

Specifically, the third voltage acquisition module includes a third standard load resistor and a third current sampling circuit. The third standard load resistor is connected to the third current sampling circuit. The third current sampling circuit is connected to the main control chip. connect.

Specifically, the accuracy levels of the first standard load resistance, the second standard load resistance and the third standard load resistance are higher than or equal to 0.01 level. The resistance values of the first standard load resistor, the second standard load resistor and the third standard load resistor are equal.

Specifically, the first voltage rise and fall circuit is used to output the voltage signal U _A. The first voltage rise and fall circuit includes an inductor L1, a diode D1, a full control device Q1, a capacitor C1 and a resistor R1;

The base of the full control device Q1 is connected to the first PWM signal, the collector of the full control device Q1 is connected to the voltage signal U _a , and the emitter of the full control device Q1 is connected to the cathode of the inductor L1 and the diode D1 respectively. , one end of the capacitor C1 and the resistor R1 is connected to the anode of the diode D1 respectively, and the other end of the capacitor C1 and the resistor R1 is connected to the inductor L1 respectively.

Specifically, the second voltage rise and fall circuit is used to output the voltage signal U _B. The second voltage rise and fall circuit includes an inductor L2, a diode D2, a full control device Q2, a capacitor C2 and a resistor R2;

The base of the full control device Q2 is connected to the second PWM signal, the collector of the full control device Q2 is connected to the voltage signal U _b , and the emitter of the full control device Q2 is connected to the cathode of the inductor L2 and the diode D2 respectively. , one end of the capacitor C2 and the resistor R2 is respectively connected to the anode of the diode D2, and the other end of the capacitor C2 and the resistor R2 is connected to the inductor L2 respectively.

Specifically, the third voltage rise and fall circuit is used to output the voltage signal U _C. The third voltage rise and fall circuit includes an inductor L3, a diode D3, a full control device Q3, a capacitor C3 and a resistor R3;

The base of the full control device Q3 is connected to the third PWM signal, the collector of the full control device Q3 is connected to the voltage signal U _b , and the emitter of the full control device Q3 is connected to the cathode of the inductor L3 and the diode D3 respectively. , one end of the capacitor C3 and the resistor R3 is respectively connected to the anode of the diode D3, and the other end of the capacitor C3 and the resistor R3 is connected to the inductor L3 respectively.

A specific application of this utility model is:

The transformer DC resistance tester controls the A-phase, B-phase, and C-phase current output according to its current current range, and loads it on the first standard load resistor, the second standard load resistor, and the third standard load resistor. Assume that the loaded currents are respectively I _a , I _b and I _c . The first current sampling circuit, the second current sampling circuit and the third current sampling circuit perform "current-to-voltage" conversion on the I _a , I _b and I _c currents output by the transformer DC resistance tester respectively, and then the three voltage signals are obtained respectively: U _a , U _b and U _c , the three voltage signals are divided into two, one is sent to the main control chip for analysis and calculation, and the other is used as the first voltage rise and fall circuit, the second voltage rise and fall circuit, and the third voltage rise and fall circuit. Control voltage input.

The calculation process is that the main control chip calculates the voltage value (the voltage values are U _A , U _B and U _C respectively) based on the current value sampled and the resistance value pre-written in the main control chip that needs to be calibrated, and then The voltage value is compared with the voltage collected by the main control chip through the current sampling circuit to obtain a proportional coefficient value. Right now:

Assume that the resistance value of the transformer DC resistance tester that currently needs to be calibrated is R ₀ , and the resistance values of the first standard load resistor, the second standard load resistor and the third standard load resistor are all R _standard . According to Ohm's law, the transformer DC resistance tester is theoretically The voltages at the A-phase, B-phase, and C-phase voltage input terminals must be respectively (can also be understood as the voltage to be output by the device):

U _A =I _a R ₀

U _B =I _b R ₀

U _C =I _c R ₀ (1)

The proportional relationship between the three voltage signals U _a , U _b , and U _c collected by the main control chip through three current sampling circuits and U _A , U _B , and _UC are respectively:

In the figure, the relationship between the voltages U _A , U _B , and U _C output by the first voltage rise and fall circuit, the second voltage rise and fall circuit, and the third voltage rise and fall circuit and U _a , U _b , and U _c are:

Since the transformer DC resistance tester has multiple current ranges, the three-way voltage rise and fall circuit designed by this device can control the voltage U _A , U _B , and U _C values to be adjusted up and down the U _a , U _b , and U _c values. It is more convenient and flexible to boost or reduce the voltage in one step. If it is necessary to make the values of the voltages U _A , U _B and U _C output by the first voltage rise and fall circuit, the second voltage rise and fall circuit and the third voltage rise and fall circuit greater than the values of U _a , U _b and U _c , then by changing T _on and the duration of T _off , so that the duration of T _on is longer than the duration of T _off , as shown in Figure 5. If it is necessary to make the values of the voltages U _A , U _B and U C output by the first voltage rise and fall circuit, the second voltage rise and fall circuit and the third voltage rise and fall circuit to be smaller than the values of U _a , U _b and _{U c ,} then by changing T The duration of _on and T _off makes the duration of T _on shorter than the duration of T _off , as shown in Figure 6.

It can be concluded from formula (3) that the main control chip only needs to control the first PWM signal, the second PWM signal, and the third PWM signal to generate three duty cycle signal values of k _A , k _B , and k _C respectively. Realize control of the output of U _A , U _B , and U _C. And send the outputs of U _A , U _B and U _C to the voltage sampling terminal of the transformer DC resistance tester for sampling. Then according to Ohm's law, the resistance values measured by the transformer DC resistance tester can be obtained as follows:

It can be concluded from formula (4) that the resistance value simulated by this sampling method is only related to the duty cycle value of the PWM signal generated by the main control chip and the resistor R _standard . By selecting the first standard load resistor, the second standard load resistor and the third standard load resistor to be above level 0.01, the accuracy level of the calibration device can be greatly improved.

This device can not only achieve continuously adjustable calibration of the DC resistance value of the transformer, but also has three current sampling circuits that can fully meet the calibration requirements of the three-circuit transformer DC resistance tester, greatly improving work efficiency. The utility model has a novel and unique concept, a specific and practical implementation plan, few components, a simple overall circuit structure, and good use value.

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments we have described are only illustrative and are not used to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention shall be covered by the scope of protection of the claims of the present invention.

Claims (8)

1. The utility model provides a transformer direct current resistance tester calibrating device which characterized in that: the device comprises a main control chip, a first voltage acquisition module, a second voltage acquisition module, a third voltage acquisition module, a first voltage lifting circuit, a second voltage lifting circuit and a third voltage lifting circuit which are respectively connected with the main control chip;

the main control chip generates a first PWM signal, a second PWM signal and a third PWM signal, and the first PWM signal, the second PWM signal and the third PWM signal respectively control the output values of the first voltage lifting circuit, the second voltage lifting circuit and the third voltage lifting circuit;

the first voltage acquisition module converts the output current of the A phase of the transformer direct current resistance tester into a voltage signal U _a The second voltage acquisition module converts the output current of the B phase of the transformer direct current resistance tester into a voltage signal U _b The third voltage acquisition module converts the output current of the C phase of the transformer direct current resistance tester into a voltage signal U _c The voltage signal U _a 、U _b And U _c Is divided into two paths, the voltage signal U _a 、U _b And U _c One path is respectively sent to the main control chip, and the other path is respectively used as the control voltage input of the first voltage lifting circuit, the second voltage lifting circuit and the third voltage lifting circuit.

2. The calibration device for a transformer direct current resistance tester according to claim 1, wherein: the first voltage acquisition module comprises a first standard load resistor and a first current sampling circuit, wherein the first standard load resistor is connected with the first current sampling circuit, and the first current sampling circuit is connected with the main control chip.

3. The calibration device for a transformer direct current resistance tester according to claim 2, wherein: the second voltage acquisition module comprises a second standard load resistor and a second current sampling circuit, wherein the second standard load resistor is connected with the second current sampling circuit, and the second current sampling circuit is connected with the main control chip.

4. A transformer direct current resistance tester calibration apparatus as recited in claim 3, wherein: the third voltage acquisition module comprises a third standard load resistor and a third current sampling circuit, wherein the third standard load resistor is connected with the third current sampling circuit, and the third current sampling circuit is connected with the main control chip.

5. The calibration device for a transformer direct current resistance tester according to claim 4, wherein: the first, second and third standard load resistors have an accuracy level greater than or equal to 0.01.

6. The calibration device for a transformer direct current resistance tester according to claim 1, wherein: the first voltage step-up/step-down circuit is used for outputting a voltage signal U _A The first voltage lifting circuit comprises an inductor L1, a diode D1, a full-control device Q1, a capacitor C1 and a resistor R1;

the base electrode of the full-control device Q1 is connected with a first PWM signal, and the collector electrode of the full-control device Q1 is connected with a voltage signal U _a The emitter of the full-control device Q1 is connected with the inductor L1 and the cathode of the diode D1 respectively, one end of the capacitor C1 and one end of the resistor R1 are connected with the anode of the diode D1 respectively, and the other end of the capacitor C1 and the other end of the resistor R1 are connected with the inductor L1 respectively.

7. The calibration device for a transformer direct current resistance tester according to claim 1, wherein: the second voltage step-up/step-down circuit is used for outputting a voltage signal U _B The second voltage lifting circuit comprises an inductor L2, a diode D2, a full-control device Q2, a capacitor C2 and a resistor R2;

the base electrode of the full-control device Q2 is connected with a second PWM signal, and the collector electrode of the full-control device Q2 is connected with a voltage signal U _b The emitter of the full-control device Q2 is connected with the cathodes of the inductor L2 and the diode D2 respectively, one ends of the capacitor C2 and the resistor R2 are connected with the anode of the diode D2 respectively, and the other ends of the capacitor C2 and the resistor R2 are connected with the inductor L2 respectively.

8. The calibration device for a transformer direct current resistance tester according to claim 1, wherein: the third voltage step-up/step-down circuit is used for outputting a voltage signal U _C The third voltage lifting circuit comprises an inductor L3, a diode D3, a full-control device Q3, a capacitor C3 and a resistor R3;

the base electrode of the full-control device Q3 is connected with a third PWM signal, and the collector electrode of the full-control device Q3 is connected with a voltage signal U _b The emitter of the full-control device Q3 is connected with the inductor L3 and the cathode of the diode D3 respectively, one end of the capacitor C3 and one end of the resistor R3 are connected with the anode of the diode D3 respectively, and the other end of the capacitor C3 and the other end of the resistor R3 are connected with the inductor L3 respectively.