How to choose the power relay correctly, which is divided into 4 steps, I hope to help everyone's learning.
1, measuring contact resistance
Use the resistance file of the universal meter to measure the normally closed contact and the dynamic point resistance, the resistance value should be 0, (the contact resistance value can be measured within 100 milliohms in a more precise way); and the normally open contact and movement The resistance of the point is infinite. This makes it possible to distinguish between a normally closed contact and a normally open contact.
2, measuring coil resistance
The resistance of the power relay coil can be measured by the universal meter R×10 Ω file to determine whether the coil has an open circuit.
3. Measure the pull-in voltage and pull-in current
Find adjustable power supply and ammeter, input a set of voltage to the power relay, and serially connect the current meter in the power supply circuit for monitoring. Slowly increase the power supply voltage. When you hear the power relay pick up, record the pull-in voltage and pull-in current. For accuracy, you can try to average and try several times.
4, measuring the release voltage and release current
It is also connected test as described above. When the power relay is pulled in, the power supply voltage is gradually reduced. When the power relay is heard to release the sound again, write down the voltage and current at this time. You can also try to get the average several times. Release voltage and release current. In the general five steps, the release voltage of the power relay is about 10 to 50% of the pull-in voltage. If the release voltage is too small (less than 1/10 of the pull-in voltage), it cannot be used normally. The stability is a threat and the selection is not reliable.
When a power relay is selected, 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 operating current to the power relay, otherwise the power relay pull-in is unstable.