(1) The voltage drop after the turn-on is large, the forward voltage drop of the thyristor or two-phase control silicon can reach 1~2V, and the saturation voltage drop of the high-power transistor is also between 1~2V, which guides the general power FET’s turn-on The resistance is also greater than the on-resistance of the machine contacts.

(2) After the semiconductor device is turned off, there may still be a few microamperes to a few milliamperes of leakage current, which is an electrical disconnection that cannot achieve the target.

(3) Due to the large voltage drop of the tube, the power consumption and heat generation after turning on are also large, and the volume of the high-power solid-state relay is larger than the volume of the electromagnetic relay of the same capacity, and the cost is also high.

(4) The temperature characteristics of electronic components and electronic circuits have poor anti-interference ability and poor radiation resistance. If no useful measures are taken, the reliability is very low.

(5) The solid state relay has a greater overload delay, and the fast fuse or RC resistor circuit is overloaded. The load of the solid state relay is related to the ambient temperature. When the temperature decreases, the load power will be flexibly reduced.

(6) The important shortcomings are the on-state voltage drop (need to respond to the heat dissipation step), the off-state leakage current, AC/DC cannot be used universally, the number of contact groups is small, other over-current, over-voltage and voltage recovery rate, current recovery rate Wait for the target difference.

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