Select a Right Solid State Relay?

If you are in need of a Solid State Relay, you may want to consider a lot of important factors, such as the SSR performance parameters and application conditions. Other important factors may include over-volt conditions and the load capacity of SSR. This is important if you want to ensure the reliability of the unit and make it stand the test of time. Given below are some tips that will help you go for the right SSR.

1. Consider the Load Types

These units can switch on and off during normal loads, but it is not the same during special load conditions. Therefore, based on your load type, you should go for the right unit. It is quite important if you don’t want to cause damage to the unit. You may not want to exceed the rated output current mentioned on the device.

Apart from this, you may want to consider the surge characteristics as well. There should be plenty of current and voltage margin.

2. Consider the DV/DT, Transient Voltage, and Power Voltage of the Circuit

If you have a DC-voltage system, make sure you go for a device that is designed for direct current. The reason is that AC Solid State Relays are designed to control AC power and load. Again, make sure that the load does not exceed the rated output voltage.

In the case of capacitive and inductive loads, the power voltage won’t be zero when the AC Solid State Relay switches off. The output ends with a higher DT/DV value. So, it is better that you go for a unit that features a high DV/DT.

3. Consider the Input Ends of the Unit

You can choose from two types of units: AC and DC input control. The latter uses a source circuit that offers constant current. In this case, the range of input voltage is between 3 and 32 volts DC. It is designed to connect with a microcomputer interface and TTL circuit.

Apart from this, you may want to pay attention to the negative and positive polarity of the terminals. In the case of an AC Solid State Relay, the voltage is between 70 and 280 volts.

4. Consider the Overheating, Overvoltage, and Overcurrent factors

In case of a short circuit or overcurrent, the Solid State Relay may get damaged. If you want to prevent this issue, we suggest that you install an air switch or fast fuse. To be on the safe side, you may want to choose units that feature MOV, in-built RC snubber circuits, and output protection. This is important if you want the unit to tolerate voltage surges.

The load capacity of these units is affected by many factors, such as the temperature of the unit itself and the ambient temperature. Therefore, make sure that there is enough heat emission during installation and usage. If the rated current is higher than 10 amperes, make sure that you install a radiator.

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