arduinoTime:
Sir TomGeorge, I'm using Sunon DP200A. Is it a brushless fan? I tried measuring the current using a multimeter but there's no difference when the fan is on and blocked. Should I put an amplifier?
The circuitry inside limits the current, most likely. Or maybe it's your power supply. What are you powering it from?
If the 1st is the case, that means 2 things.
1) you can't protect it by shutting it off when it gets stuck
2) you probably don't need too
Sorry, missed the fact they are mains driven.