Is the relay AC or DC?

Some people have a lot of confusion when choosing DC relays or AC relays. For example: the relay input is DC and the output is AC; or you want the input to be AC ​​and the output to be DC; or DC to DC, AC to AC, can you? Regarding the difference between a DC relay and an AC relay, the biggest difference is that the power supply of the DC relay must be DC, the power supply of the AC relay must be AC ​​power, the DC resistance of the DC relay coil is large, and the number of turns of the AC relay coil is correspondingly small.

Working principle distinction

The working principles of DC relays and AC relays are basically the same, and they are based on electromagnetic principles, but the power supply of DC relays must be DC, and the power supply of AC relays must be AC ​​power. The DC resistance of the DC relay coil is very large, and the coil current is equal to the voltage divided by the DC resistance of the coil, so the coil wire is thin and has many turns.

Structural feature distinction

The coil of the AC relay is short, and the wire diameter is relatively thick, mainly because the reactance of the coil is relatively large after the alternating current is applied, and the thick wire diameter can reduce the internal resistance and heat generation. When the magnetic field changes, an eddy current is formed when the short-circuit ring is formed, and an electromagnetic force opposite to the direction of the magnetic field change is formed, which lags the change of the magnetic field. , so that the electromagnet can be better attracted. Since the DC relay does not generate reactance when it is connected to DC, the coil diameter of the DC relay is relatively small, mainly to increase the internal resistance and prevent the short circuit phenomenon. Because of the large heat generated during operation, the relay is made higher. Longer, mainly for good heat dissipation.