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Related principles of current relays

The working principle of the current relay:

The working principle is that a magnetic field is generated after the coil is energized, and then the iron piece connected to the contact is sucked in, so that the circuit path can reach the purpose of maintaining the circuit. The common connection method is that the two wires of the coil are one positive and one negative, and one of them is opened to open. The other wires are connected to the consumer.

Current relays are generally made of imported integrated circuits. After the measured AC current passes through the isolated AC, it will get a voltage U1 proportional to the measured current. Stop the rectification after the setting and setting treatment. After the rectified voltage passes the filter, the DC voltage U0 proportional to U1 will be obtained, and then the DC voltage will stop comparing with the DC reference voltage. The level detector will output a positive signal to put the relay in a working state. If the reference voltage is lower than the DC voltage, the level detector will output a negative signal, which will cause the relay to be inactive. The RL series static current relay is used for overload and short-circuit maintenance installation of generators, transformers and power lines. Starting element.

Construction principle

When the circuit is over-current, the relay will act according to the inverse time or definite time delay and cut off the circuit, and the inverse time or definite time and the length of the delay time can be sensitively selected by the toggle switch. Static current relay, using imported integrated circuits. After the measured AC current I ~ passes through the isolated converter, a voltage Ui proportional to the measured current is obtained at its secondary. Rectification is stopped after the setting of the set value, and the rectified pulse voltage is filtered by a filter to obtain a DC voltage Uo that is proportional to Ui. In the level detection, Uo stops comparing with the DC reference voltage Ue. If the DC voltage Uo is lower than the reference voltage, the level detector outputs a positive signal to drive the outlet relay and the relay is in the operating state. On the contrary, if the DC voltage Uo is higher than the reference voltage Ue, the level detector outputs a negative signal, and the relay is inactive.

Common tests

1. To measure the resistance of a contact, use the resistance file of a tool meter to measure the resistance of a normally closed contact and a moving point. The resistance should be 0 (the contact resistance can be measured within 100 milliohms with more accurate methods); and The resistance between the normally open contact and the moving point is infinitely large. This makes it possible to distinguish between a normally closed contact and a normally open contact.

2. To measure the resistance of the coil, the resistance value of the relay coil can be measured with the tool table R & TImes; 10Ω, so as to determine whether the coil has an open circuit phenomenon.

3. Measure the pull-in voltage and pull-in current to find an adjustable regulated power supply and ammeter, input a set of voltage to the relay, and insert a current meter in the power supply circuit to stop monitoring. Gradually increase the power supply voltage. When you hear the relay pull-in sound, note the pull-in voltage and pull-in current. For accuracy, you can try several times to find the uniform value.

4. Measuring the release voltage and release current is also the connection test as above. When the relay is activated, the power supply voltage is gradually reduced. When you hear the release sound of the relay again, note the voltage and current at this time. You can also try Several times to obtain a uniform release voltage and release current. Under normal conditions, the release voltage of the relay is about 10-50% of the pull-in voltage. If the release voltage is too small (less than 1/10 of the pull-in voltage), it can not be used normally, which will cause the stability of the circuit. , Work is not reliable.

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