I need to control a load of 12v DC and 30A, Can I control the load with an AC solid-state-relay 24-380v and 40A? If it isn't possible, what should I use? Thanks.
No you can't.
Figure 1. The SSR-40 DA.
I need to control a load of 12v DC and 30A ...
The device clearly shows that:
- The output (pins 1 and 2) are AC. It can not switch DC.
- The output will switch 24 V to 380 V AC. Even if it could handle DC your voltage is too low.
If it isn't possible, what should I use?
A relay or a DC SSR with voltage and current ratings to suit.
what should I use?
You can control a 30A DC load of any reasonable voltage with a suitable MOSFET. Your options are wider if the gate control voltage is 10 volts or above. For switching 12 volts, I'd look at 20 volt rated devices with an on-resistance in the milli ohm range. For a 10 milli ohm on-resistance at 30 A, the power dissipation is going to be 9 watts so, some form of heatsinking will be required.
You can get a few MOSFETs that are around 1 milli ohm of course.
To make this work with reliability you need to have an under-voltage lock-out system should the 12 volts drop to below 10 volts. This prevents the MOSFET being turned on when it can only achieve an on-resistance of maybe 100 milli ohm to avoid burn-out.
If you are switching an inductive load you will need to use a flyback catch diode rated potentially at full load current.