①Measure contact resistance: use the electrical barrier of a multimeter to measure the resistance of the normally closed contact and the moving point. The resistance value should be 0; and the resistance value of the normally open contact and the moving point is infinite. From this, it can be distinguished which is a normally closed contact and which is a normally open contact.
②Measure the coil resistance: use a multimeter to measure the resistance of the relay coil in the R×10 block, so as to judge whether the coil has an open circuit.
③Measure the pull-in voltage and pull-in current: use an adjustable regulated power supply and an ammeter to input a set of voltage to the relay, and insert an ammeter in the power supply loop for monitoring. Slowly increase the power supply voltage, and record the pull-in voltage and pull-in current when you hear the sound of the relay pull-in. For accuracy, you can try to average multiple times.
④Measure the release voltage and release current: also connect and test like the above. When the relay pulls in, gradually reduce the supply voltage. When the relay releases sound again, write down the voltage and current at this time. You can also try Get the average release voltage and release current several times. Under normal circumstances, the release voltage of the relay is 10%~50% of the pull-in voltage. If the release voltage is smaller than 1/10 of the pull-in voltage, it cannot be used normally, which will threaten the stability of the circuit and make it work. Unreliable.
The relay is a key component in the smart prepaid electric energy meter. The life of the relay determines the service life of the electric meter to a certain extent. The performance of this device is very important to the operation of the smart prepaid electric energy meter. However, there are many relay manufacturers at home and abroad, the production scale is quite different, the technical level is very different, and the performance parameters are very different. Therefore, the electric energy meter manufacturer must have a complete set of detection devices in the relay detection and selection to ensure the quality of the meter. At the same time, * Grid has also strengthened the sampling test of the relay performance parameters in the smart electric energy meter. Corresponding testing equipment is also required to test the quality of the meters produced by different manufacturers. However, the relay testing equipment not only has a single test item, the test process cannot be automated, the test data needs to be processed and analyzed manually, and the test results have various random and artificial characteristics, and the detection efficiency is low, and the safety is not guaranteed.
In the past two years, *Grid has gradually standardized the technical requirements of electric meters and formulated relevant industry standards and technical specifications. This has raised some technical problems for relay parameter detection, such as relay load making and breaking capacity, switching characteristic testing, etc. Therefore, there is an urgent need to study a kind of equipment 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 test items without load current, such as action value, contact resistance, and mechanical life; the other is the test items with load current, such as contacts. Contact voltage, electrical life, overload capacity.
The main test items are briefly introduced as follows: (1) Action value. The required voltage value when the relay is activated. (2) Contact resistance of contacts. When the electric shock is closed, the resistance value between the two contacts. (3) Mechanical life. The number of times the relay is switched on and off repeatedly without damage to the mechanical part. (4) Contact voltage. When the electric shock is closed, a certain load current is applied to the electric shock circuit, and the voltage value between the contacts is applied. (5) Electrical life. When the rated voltage is applied to both ends of the relay driving coil and the rated resistive load is applied to the contact circuit, the number of reliable actions of the relay under the condition of less than 300 cycles per hour and a duty ratio of 1:4. (6) Overload capacity. When the rated voltage is applied to both ends of the relay drive coil and 1.5 times the rated load is applied to the contact circuit, the number of reliable actions of the relay under the condition of the operating frequency (10±1) times/min.
The relay coil is represented by a long box symbol in the circuit. If the relay has two coils, draw two parallel long boxes. At the same time, mark the text symbol "J" of the relay in or beside the long box. There are two ways to represent the contacts of the relay: one is to draw them directly on the side of the long box, which is more intuitive. The other is to draw each contact into its own control circuit according to the needs of circuit connection. Usually the same text symbol is marked next to the contact and coil of the same relay, and the contact group is numbered. To show the difference.
There are 3 basic forms of relay contacts:
(1) The two contacts of the moving-on type (normally open, H-type) coil are disconnected when the coil is not energized, and the two contacts are closed after energization. It is represented by the pinyin prefix "H" of the word "合".
(2) The two contacts of the movable-break type (normally closed, D-type) coil are closed when the coil is not energized, and the two contacts are disconnected after energization. It is indicated by the pinyin prefix "D" of the word "break".
(3) The conversion type (Z type) is a contact group type. This kind of contact group has 3 contacts in total, that is, the middle is a moving contact, and the upper and lower are static contacts. When the coil is not energized, the movable contact is disconnected from one of the static contacts, and closed with the other; after the coil is energized, the movable contact moves to make the original open state closed and the original closed open state, reaching The purpose of the conversion. Such a contact group is called a changeover contact. It is indicated by the pinyin prefix "Z" of the word "zhuan".