Can i use a 12 v 5 amp power supply inplace of a 12 v 3 amp power supply?

Yes, you can use a 12V 5 amp power supply in place of a 12V 3 amp power supply. The higher amp rating means the power supply can provide more current if needed, but it will only supply what the device requires, which is 3 amps in this case. Just ensure that the voltage matches and that the power supply is compatible with your device's requirements.