What do you need to know about solid state relays?
The relay may be designed to switch either AC or DC to the load. It serves the same function as an electromechanical relay, but has no moving parts . Packaged solid-state relays use power semiconductor devices such as thyristors and transistors, to switch currents up to around a hundred amperes.
How does a DC switching relay ( SSR ) work?
The power semiconductor in the DC switching relay operates in accordance with the control input. The response time is less than 100ms. DC switching SSRs are used with resistive and inductive loads for the control of DC motors and valves.
What are the Derating curves for solid state relays?
Derating Curves 10 50 100 500 01 2 3 4 5 6 7 24-VDC resistive load 110-VAC resistive load 220-VAC resistive load Contact current (A) Number of operations ( × 10 4 4 500 01 2 3 24-VDC inductive load L/R = 7 ms 110-VAC inductive load cosφ = 0.4 220-VAC inductive load Number of operations ( cosφ = 0.4 × 10 4 ) Contact current (A)
How is optical coupling used in solid state relays?
The optical coupling allows the control circuit to be electrically isolated from the load. See opto-isolator for more information about this isolation technique. An SSR based on a single MOSFET, or multiple MOSFETs in a paralleled array, can work well for DC loads.
It is required to equip the SSR with the overload protective device. When selecting a solid state relay, the SSR with higher rated current should be selected if possible, so as to guarantee the enough current margin. 2. SSR DC or AC type
What should I do when my SSR is turned off?
The SSR may be damaged by counterelectromotive force from the motor. Be sure to install overcurrent protection for when the SSR is turned OFF. 4.Transformer Load When the SSR is switched ON, an energizing current of 10 to 20 times the rated current flows through the SSR for 10 to 500 ms.
Can a surge current damage a solid state relay?
In addition, the surge current of the load may also damage the solid state relay if it exceeds the overloading capability of SSR. For the above issue, the solid state relay should be selected properly based on the different types of loads.
What causes a solid state relay burnout?
During the usage of SSR, it might cause the burning if the working conditions of different relays are not concerned , or improper using of the solid state relay may also result in the sudden immediate burning in just purchasing.