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 gear to determine whether the coil is open.
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 connect 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 power supply voltage. When you hear the relay release 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 intelligent prepaid electric energy meter. The life of the relay determines the life of the electric meter to a certain extent. The performance of this device is very important to the operation of the intelligent prepaid electric energy meter. However, there are many relay manufacturers at home and abroad, the production scale is quite different, the technical level is far apart, and the performance parameters are vastly 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, the State Grid has also strengthened the sampling test of the relay performance parameters in the smart electric energy meter. Corresponding testing equipment is also needed to inspect the quality of the meters produced by different manufacturers. However, the relay testing equipment not only has a single testing item, the testing process cannot be automated, the testing data needs to be processed and analyzed manually, and the testing results are random and artificial, and the testing efficiency is low, and the safety is not guaranteed.
In the past two years, the State Grid has gradually standardized the technical requirements for electric meters and formulated relevant industry standards and technical specifications. This has raised some technical problems for relay parameter testing, 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 a rated voltage is applied to both ends of the relay driving coil and a 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 operating frequency (10±1) times/min.
The relay coil is represented by a rectangular box symbol in the circuit. If the relay has two coils, draw two parallel rectangular 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 symbols are marked next to the contacts and coils of the same relay, and the contact groups are 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.
(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.
(3) 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.