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Measurements Taken to Test Relays

1.Testing Contact Resistance
We can use the multimeter resistance to measure the resistance of constant closed contact and moving point, its resistance value should be 0, and the resistance value of constant open contact and moving point is infinite. It is thus possible to distinguish between a normally closed contact and a normally open contact.

2.Measuring Coil Resistance
The resistance of relay coil can be measured by multimeter R×10, so that the open circuit phenomenon of the coil can be judged.

3.Measuring the Tap-in Voltage and Tap-in Current
We need to input a set of voltage to the relay with an adjustable regulated power supply and ammeter, and then put Ammeter in series in the power supply circuit for monitoring. Slowly turn up the power supply voltage. When you hear the sound of the relay closing, record the closing voltage and current. To be accurate, you can try averaging several times.

4.Measuring of Release Voltage and Release Current
Applying the same test as above mentioned, when the relay is engaged, then we can gradually lower the supply voltage, when the relay is heard again release sound, note the voltage and current at this time. We can also try many times to achieve an average release voltage and release current. In general, the release voltage of the relay is 10% ~ 50% of the closing voltage. If the release voltage is less than 1/10 of the closing voltage, it can not be normally used, which will threaten the stability of the circuit and make work unreliable.
The relay is the key device of the intelligent prepaid watt-hour meter, the life of the relay determines the life of the meter to some extent, the performance of the device is very important to the operation of the intelligent prepaid watt-hour meter. However, there are many relay manufacturers at home and abroad, the production scale varies greatly, the technical level varies greatly, and the performance parameters vary widely. Therefore, the electric energy meter manufacturer must have a set of perfect testing device when the relay is tested and selected, in order to ensure the quality of the electric meter. At the same time, the grid has also strengthened the sampling test of relay performance parameters in smart meters, and the corresponding test equipment is also needed to test the quality of meters produced by different manufacturers. However, the relay testing equipment not only has a single testing item, the testing process can not be automated, the testing data need to be manually processed and analyzed, and the testing results are random and artificial, and, the detection efficiency is low, and the security can not be guaranteed.
In the past two years, the power grid has gradually standardized the technical requirements of electric meters, formulated relevant industry standards and technical specifications, which have raised some technical difficulties for the detection of relay parameters, such as relay load on-off ability, switch characteristics testing. Therefore, there is an urgent need to study a device to realize the comprehensive detection of relay performance parameters. According to the test requirements of relay performance parameters, the test items can be divided into two categories: one is the items without load current, such as action value, contact resistance, mechanical life; Second, with the load current test items, such as contact voltage, electrical life, overload capacity. The main test items are as follows: (1) action value. The value of voltage required when the relay operates. Contact resistance. The value of the resistance between two contacts when the contact is closed. (3) mechanical life. Mechanical parts in the case of no damage, the relay repeatedly switching action number. (4) contact voltage. When the electric shock is closed, a certain load current is applied in the electric shock circuit, and the voltage value between contacts. (5) electrical life. When the rated voltage is applied at both ends of the relay driving coil and the rated resistive load is applied in the contact circuit, the reliable operation frequency of the relay is less than 300 cycles per hour and the duty cycle is 1∶4. (6) overload capacity. When the rated voltage is applied at the two ends of the relay driving coil and 1.5 times rated load is applied in the contact circuit, the reliable operation frequency of the relay is (10 ± 1) times per minute.

Symbol representation method
Relay coils are represented in a circuit by a rectangular symbol. If the relay has two coils, draw two parallel rectangular boxes. At the same time in the rectangular box or rectangular box on the text symbol relay “J”. Relay contacts are represented in two ways: one is to draw them directly on the side of the rectangle, which is more intuitive. The other is to draw each contact into its own control circuit according to the need of circuit connection. Usually, the contact points and coils of the same relay are marked with the same character symbols and the contact groups are numbered, to make a difference.

Three Basic Types of Relay Contacts
(1)the two contacts are opened when the power is not connected to the moving coil (normally open, H Type) , and the two contacts are closed when the power is connected to the coil. It is denoted by the initial “h” of the Chinese character “he”.
(2) the two contact points are closed when the coil is not energized, and the two contact points are disconnected when the coil is energized. It is denoted by the phonetic prefix “d” of the word “break”.
(3) the transfer type (Z Type) is the contact type. The Contact Group has three contacts, namely, the middle is the dynamic contact, up and down a static contact. When the coil is not energized, the moving contact is disconnected from one of the static contacts and closed with the other; when the coil is energized, the moving contact moves, making the previously disconnected closed and the previously closed open, for the purpose of transformation. Such a contact group is called a transition contact. It is denoted by the phonetic prefix “z” of the word “turn”.

Post time: May-27-2022