Hi...

I have 3 volt ac power supply, and I want to power up a motor which is has requirement 12 volt dc power.. what should I do?

Judgeing from this and your other questons, this seems part of a test of some sort.

It's asked in real general terms too, so it could be answered in a general fashion, but first I have to ask some questions:

1. What kind of power (in watts) is expected.
2. What is the input power (in watts) available.

Hello Fakhri_Achmad

If you have a (single phase) 3 volt ac power supply, and you want to power up a motor which needs 12 volt dc, you can :

1 - use a different power source (other transformer and rectifier)
2 - use a 'switching' converter 3 V ac to 12 V dc
3 - use a quadruppling circuit (small currents only) with 4 diodes + 4 capacitors.

Note : your data do not refer to power requirements involved. My answer do neither.

@ sarnian & Keepitsimple

Would I need any clamper?

Hello Fakhri_Achmad

What do you mean with clamper? Cable clamp? You need that clamper... to do what? (connecting to the rectifier unit?)

Still waiting for information on power requirements of motor and capacity of available power supply.

Examples (please fill in the correct values) :

The motor requires 12 Volt DC at ___ Amp.
The power supply provides 3 Volt AC at ___ Amp max.
Does the transformer provide the 3 Volt AC over a single secundary winding, do you have 2 windings of 3 Volt, or 2 windings of 3 volt with a nil in between?

If you want to receive proper advice, you need to provide this information first !