1. Measure the resistance of the contact
Use the resistance level of the universal meter to measure the resistance of the normally closed contact and the moving point, and its resistance value should be 0, (the contact resistance value can be measured in a more accurate way within 100 milliohms); The resistance between the normally open contact and the moving point is infinite. From this, it is possible to distinguish which is a normally closed contact and which is normally open.
2. Test the coil resistance
The resistance of the power relay coil can be measured in the R×10Ω position of the universal meter, so as to determine whether the coil has an open circuit.
3. Measure the pick-up voltage and pick-up current
Find an adjustable regulated power supply and an ammeter, input a set of voltages to the power relay, and connect the ammeter in the power supply circuit for monitoring. Slowly increase the power supply voltage, and when you hear the power relay sucking sound, make a note of the sucking voltage and sucking current. To be accurate, you can try several times to find the average.
4. Measure the release voltage and release current
It is also the same as the above connection test, when the power relay is engaged, and then gradually reduce the supply voltage, when you hear the power relay release sound again, write down the voltage and current at this time, you can also try several times to obtain the average release voltage and release current. Under normal circumstances, the release voltage of the power relay is about 10-50% of the pick-up voltage, if the release voltage is too small (less than 1/10 of the pick-up voltage), it can not be used normally, which will threaten the stability of the circuit, and the selection is unreliable.
1. Understand the necessary conditions first
(1) The maximum current that can be provided by the five steps of the power supply voltage of the control circuit;
(2) the voltage and current in the controlled circuit;
(3) How many sets and what forms of contacts are required for the controlled circuit. When selecting power relays, the power supply voltage of the general control circuit can be used as the basis for selection. The control circuit should be able to provide sufficient working current to the power relay, otherwise the power relay engagement is unstable.
2. After consulting the relevant information to determine the conditions of use, you can search for the relevant information to find out the model and specification number of the power relay that requires five steps. If you already have a power relay on hand, you can check whether it can be used based on the information. Finally, consider whether the size is appropriate.
3. Pay attention to the volume of the appliance. If it is used for general electrical appliances, in addition to considering the chassis volume, the small power relay mainly considers the circuit board installation layout. For small electrical appliances, such as toys and remote control devices, ultra-small power relay products should be selected.
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