Homemade relay voltage and current parameter calibrator

Homemade relay voltage and current parameter calibrator

The author has developed a voltage and current relay setting value verification tester for relay protection, which is convenient for technicians to verify and adjust the setting value of the relay.

When assembling the relay protection screen, in order to ensure the reliable operation of the protection screen, the purchased relay action voltage, action current, release voltage and release current values ​​must be checked every time. These items are completed by a calibrator purchased from us. The advantage of this purchased calibrator is that it is fully functional. In addition to calibrating voltage and current, it can also calibrate relay parameters such as impedance and frequency. The disadvantage is that the calibrator is very large, about the size of a household suitcase, and very heavy. It must be lifted by two people every time it is used, which is very inconvenient to use. For this reason, we decided to make a simple calibrator ourselves. To measure the voltage and current values ​​that are generally calibrated frequently, and abandon the calibration function of uncommon parameters, and the selected devices should be as small as possible while meeting the requirements, so that the size of the calibrator is greatly reduced and portable.

The circuit principle is shown in Figure 1, and the actual schematic is shown in Figure 2.

1. Circuit structure

1. The current relay verification circuit is composed of a single-phase auto voltage regulator TY, a high-voltage capacitor C, a current transformer LH, a jog button AN2, an output current switch S2 and an ammeter A.

2. The voltage relay verification circuit is composed of the voltage regulator TY, the rectifier bridge QL, the DC output switch S1, the inching button AN1 and the voltmeter v.

In the current relay verification circuit, the purpose of connecting the capacitor C in series on the primary side of the current transformer LH is to increase the impedance of the output circuit of the voltage regulator. This is done to prevent the voltage regulator from being burned out if the output voltage of the voltage regulator is adjusted too high due to the impedance of the output circuit of the voltage regulator being too low. Secondly, it will make the operation too sensitive. As long as the output voltage of the voltage regulator is adjusted a little, the current on the secondary side of the current transformer LH will be very large, making it difficult to make fine adjustments and unable to ensure the adjustment accuracy.

2. Current relay verification

Step 1: First, adjust the setting value of the current relay to be tested (such as 10A), and connect its coil to terminals 3 and 4 in Figure 1, and adjust the voltage regulator to zero.

Step 2: Close the power switch S on the panel of the tester, the power indicator LED will light up, and the voltage regulator will be energized. Then close the switch S2 and slowly turn the hand wheel of the voltage regulator to increase its output voltage from zero. Through the coupling of the current transformer LH, the current on the secondary side will also increase until the current relay is activated and pulled in.

Step 3: Keep the voltage regulator in place, disconnect S2, return the current relay, press the inching button AN2, the current relay should operate reliably (otherwise the voltage regulator input voltage should be fine-tuned), then read the value of the ammeter and record it.

Step 4: Close switch S2 again, lower the output voltage of the voltage regulator, return the current relay, increase the output voltage of the voltage regulator again, make the current relay actuate and close... and repeat step 3. Repeat the above process three times, and take the average value as the actuating current value of the current relay. The smaller the difference between this actuating value and its setting value, the better, indicating that the actuating accuracy of the current relay is high and qualified. Absolute value of error {(setting value - actuating value) / setting value} *%

After completing the above steps, close S2 and slowly reduce the output voltage of the voltage regulator so that the current relay just returns. At this time, record the value of the ammeter. Repeat this process three times. The average value is the return value of the current relay. Compared with this value and the set value, the smaller the difference, the smaller the delay of the current relay and the higher the action sensitivity.

After all tests are completed, adjust the voltage regulator to zero and disconnect the power switch S.

3. Calibration of voltage relay

First, adjust the setting value of the voltage relay to be calibrated, and connect its coil to the terminals 5 and 6 of the calibrator. Check that the voltage regulator is at zero position, and close the power switch S and the DC output switch S1. Slowly increase the output voltage of the voltage regulator so that the voltage relay just works. Keep the output voltage of the voltage regulator unchanged, disconnect S1 and press AN1, and the voltage relay should work reliably. Record the value of the voltmeter. This process should be repeated three times, and the average value is the action voltage value. The measurement method of the return value and the evaluation of the performance of the relay are similar to the calibration of the current relay, so it will not be described in detail here.

4. Determination of component parameters

1. The voltage regulator TY can be a 90W miniature one, because it works for a short time and mainly checks relays within 10A.

2. For buttons and switches, select any one with a rating of 10A or above and a small size.

3. The current transformer LH needs to be made by yourself. Find a LMZ100/5 current transformer, pry open its shell, remove the coil, insulate the iron core with insulating tape, and then use 1mm diameter enameled wire to wind 100 turns as the primary winding. Use 1.2mm diameter enameled wire to wind 10 turns as the secondary winding. The primary and secondary windings should be insulated and wrapped, and finally dipped in varnish and dried. Other parameters are shown in Figure 1.

5. Calibrator parameters

1. Use power supply voltage 220VAC

2. Maximum output current 15A

3. Maximum output voltage 250VAC

4. Working method: short-time working system